/*
* Freescale GPMI NAND Flash Driver
*
* Copyright (C) 2008-2011 Freescale Semiconductor, Inc.
* Copyright (C) 2008 Embedded Alley Solutions, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/slab.h>
#include "gpmi-nand.h"
#include "gpmi-regs.h"
#include "bch-regs.h"
static struct timing_threshod timing_default_threshold = {
.max_data_setup_cycles = (BM_GPMI_TIMING0_DATA_SETUP >>
BP_GPMI_TIMING0_DATA_SETUP),
.internal_data_setup_in_ns = 0,
.max_sample_delay_factor = (BM_GPMI_CTRL1_RDN_DELAY >>
BP_GPMI_CTRL1_RDN_DELAY),
.max_dll_clock_period_in_ns = 32,
.max_dll_delay_in_ns = 16,
};
#define MXS_SET_ADDR 0x4
#define MXS_CLR_ADDR 0x8
/*
* Clear the bit and poll it cleared. This is usually called with
* a reset address and mask being either SFTRST(bit 31) or CLKGATE
* (bit 30).
*/
static int clear_poll_bit(void __iomem *addr, u32 mask)
{
int timeout = 0x400;
/* clear the bit */
writel(mask, addr + MXS_CLR_ADDR);
/*
* SFTRST needs 3 GPMI clocks to settle, the reference manual
* recommends to wait 1us.
*/
udelay(1);
/* poll the bit becoming clear */
while ((readl(addr) & mask) && --timeout)
/* nothing */;
return !timeout;
}
#define MODULE_CLKGATE (1 << 30)
#define MODULE_SFTRST (1 << 31)
/*
* The current mxs_reset_block() will do two things:
* [1] enable the module.
* [2] reset the module.
*
* In most of the cases, it's ok.
* But in MX23, there is a hardware bug in the BCH block (see erratum #2847).
* If you try to soft reset the BCH block, it becomes unusable until
* the next hard reset. This case occurs in the NAND boot mode. When the board
* boots by NAND, the ROM of the chip will initialize the BCH blocks itself.
* So If the driver tries to reset the BCH again, the BCH will not work anymore.
* You will see a DMA timeout in this case. The bug has been fixed
* in the following chips, such as MX28.
*
* To avoid this bug, just add a new parameter `just_enable` for
* the mxs_reset_block(), and rewrite it here.
*/
static int gpmi_reset_block(void __iomem *reset_addr, bool just_enable)
{
int ret;
int timeout = 0x400;
/* clear and poll SFTRST */
ret = clear_poll_bit(reset_addr, MODULE_SFTRST);
if (unlikely(ret))
goto error;
/* clear CLKGATE */
writel(MODULE_CLKGATE, reset_addr + MXS_CLR_ADDR);
if (!just_enable) {
/* set SFTRST to reset the block */
writel(MODULE_SFTRST, reset_addr + MXS_SET_ADDR);
udelay(1);
/* poll CLKGATE becoming set */
while ((!(readl(reset_addr) & MODULE_CLKGATE)) && --timeout)
/* nothing */;
if (unlikely(!timeout))
goto error;
}
/* clear and poll SFTRST */
ret = clear_poll_bit(reset_addr, MODULE_SFTRST);
if (unlikely(ret))
goto error;
/* clear and poll CLKGATE */
ret = clear_poll_bit(reset_addr, MODULE_CLKGATE);
if (unlikely(ret))
goto error;
return 0;
error:
pr_err("%s(%p): module reset timeout\n", __func__, reset_addr);
return -ETIMEDOUT;
}
static int __gpmi_enable_clk(struct gpmi_nand_data *this, bool v)
{
struct clk *clk;
int ret;
int i;
for (i = 0; i < GPMI_CLK_MAX; i++) {
clk = this->resources.clock[i];
if (!clk)
break;
if (v) {
ret = clk_prepare_enable(clk);
if (ret)
goto err_clk;
} else {
clk_disable_unprepare(clk);
}
}
return 0;
err_clk:
for (; i > 0; i--)
clk_disable_unprepare(this->resources.clock[i - 1]);
return ret;
}
#define gpmi_enable_clk(x) __gpmi_enable_clk(x, true)
#define gpmi_disable_clk(x) __gpmi_enable_clk(x, false)
int gpmi_init(struct gpmi_nand_data *this)
{
struct resources *r = &this->resources;
int ret;
ret = gpmi_enable_clk(this);
if (ret)
goto err_out;
ret = gpmi_reset_block(r->gpmi_regs, false);
if (ret)
goto err_out;
/*
* Reset BCH here, too. We got failures otherwise :(
* See later BCH reset for explanation of MX23 handling
*/
ret = gpmi_reset_block(r->bch_regs, GPMI_IS_MX23(this));
if (ret)
goto err_out;
/* Choose NAND mode. */
writel(BM_GPMI_CTRL1_GPMI_MODE, r->gpmi_regs + HW_GPMI_CTRL1_CLR);
/* Set the IRQ polarity. */
writel(BM_GPMI_CTRL1_ATA_IRQRDY_POLARITY,
r->gpmi_regs + HW_GPMI_CTRL1_SET);
/* Disable Write-Protection. */
writel(BM_GPMI_CTRL1_DEV_RESET, r->gpmi_regs + HW_GPMI_CTRL1_SET);
/* Select BCH ECC. */
writel(BM_GPMI_CTRL1_BCH_MODE, r->gpmi_regs + HW_GPMI_CTRL1_SET);
/*
* Decouple the chip select from dma channel. We use dma0 for all
* the chips.
*/
writel(BM_GPMI_CTRL1_DECOUPLE_CS, r->gpmi_regs + HW_GPMI_CTRL1_SET);
gpmi_disable_clk(this);
return 0;
err_out:
return ret;
}
/* This function is very useful. It is called only when the bug occur. */
void gpmi_dump_info(struct gpmi_nand_data *this)
{
struct resources *r = &this->resources;
struct bch_geometry *geo = &this->bch_geometry;
u32 reg;
int i;
dev_err(this->dev, "Show GPMI registers :\n");
for (i = 0; i <= HW_GPMI_DEBUG / 0x10 + 1; i++) {
reg = readl(r->gpmi_regs + i * 0x10);
dev_err(this->dev, "offset 0x%.3x : 0x%.8x\n", i * 0x10, reg);
}
/* start to print out the BCH info */
dev_err(this->dev, "Show BCH registers :\n");
for (i = 0; i <= HW_BCH_VERSION / 0x10 + 1; i++) {
reg = readl(r->bch_regs + i * 0x10);
dev_err(this->dev, "offset 0x%.3x : 0x%.8x\n", i * 0x10, reg);
}
dev_err(this->dev, "BCH Geometry :\n"
"GF length : %u\n"
"ECC Strength : %u\n"
"Page Size in Bytes : %u\n"
"Metadata Size in Bytes : %u\n"
"ECC Chunk Size in Bytes: %u\n"
"ECC Chunk Count : %u\n"
"Payload Size in Bytes : %u\n"
"Auxiliary Size in Bytes: %u\n"
"Auxiliary Status Offset: %u\n"
"Block Mark Byte Offset : %u\n"
"Block Mark Bit Offset : %u\n",
geo->gf_len,
geo->ecc_strength,
geo->page_size,
geo->metadata_size,
geo->ecc_chunk_size,
geo->ecc_chunk_count,
geo->payload_size,
geo->auxiliary_size,
geo->auxiliary_status_offset,
geo->block_mark_byte_offset,
geo->block_mark_bit_offset);
}
/* Configures the geometry for BCH. */
int bch_set_geometry(struct gpmi_nand_data *this)
{
struct resources *r = &this->resources;
struct bch_geometry *bch_geo = &this->bch_geometry;
unsigned int block_count;
unsigned int block_size;
unsigned int metadata_size;
unsigned int ecc_strength;
unsigned int page_size;
unsigned int gf_len;
int ret;
if (common_nfc_set_geometry(this))
return !0;
block_count = bch_geo->ecc_chunk_count - 1;
block_size = bch_geo->ecc_chunk_size;
metadata_size = bch_geo->metadata_size;
ecc_strength = bch_geo->ecc_strength >> 1;
page_size = bch_geo->page_size;
gf_len = bch_geo->gf_len;
ret = gpmi_enable_clk(this);
if (ret)
goto err_out;
/*
* Due to erratum #2847 of the MX23, the BCH cannot be soft reset on this
* chip, otherwise it will lock up. So we skip resetting BCH on the MX23.
* On the other hand, the MX28 needs the reset, because one case has been
* seen where the BCH produced ECC errors constantly after 10000
* consecutive reboots. The latter case has not been seen on the MX23
* yet, still we don't know if it could happen there as well.
*/
ret = gpmi_reset_block(r->bch_regs, GPMI_IS_MX23(this));
if (ret)
goto err_out;
/* Configure layout 0. */
writel(BF_BCH_FLASH0LAYOUT0_NBLOCKS(block_count)
| BF_BCH_FLASH0LAYOUT0_META_SIZE(metadata_size)
| BF_BCH_FLASH0LAYOUT0_ECC0(ecc_strength, this)
| BF_BCH_FLASH0LAYOUT0_GF(gf_len, this)
| BF_BCH_FLASH0LAYOUT0_DATA0_SIZE(block_size, this),
r->bch_regs + HW_BCH_FLASH0LAYOUT0);
writel(BF_BCH_FLASH0LAYOUT1_PAGE_SIZE(page_size)
| BF_BCH_FLASH0LAYOUT1_ECCN(ecc_strength, this)
| BF_BCH_FLASH0LAYOUT1_GF(gf_len, this)
| BF_BCH_FLASH0LAYOUT1_DATAN_SIZE(block_size, this),
r->bch_regs + HW_BCH_FLASH0LAYOUT1);
/* Set *all* chip selects to use layout 0. */
writel(0, r->bch_regs + HW_BCH_LAYOUTSELECT);
/* Enable interrupts. */
writel(BM_BCH_CTRL_COMPLETE_IRQ_EN,
r->bch_regs + HW_BCH_CTRL_SET);
gpmi_disable_clk(this);
return 0;
err_out:
return ret;
}
/* Converts time in nanoseconds to cycles. */
static unsigned int ns_to_cycles(unsigned int time,
unsigned int period, unsigned int min)
{
unsigned int k;
k = (time + period - 1) / period;
return max(k, min);
}
#define DEF_MIN_PROP_DELAY 5
#define DEF_MAX_PROP_DELAY 9
/* Apply timing to current hardware conditions. */
static int gpmi_nfc_compute_hardware_timing(struct gpmi_nand_data *this,
struct gpmi_nfc_hardware_timing *hw)
{
struct timing_threshod *nfc = &timing_default_threshold;
struct resources *r = &this->resources;
struct nand_chip *nand = &this->nand;
struct nand_timing target = this->timing;
bool improved_timing_is_available;
unsigned long clock_frequency_in_hz;
unsigned int clock_period_in_ns;
bool dll_use_half_periods;
unsigned int dll_delay_shift;
unsigned int max_sample_delay_in_ns;
unsigned int address_setup_in_cycles;
unsigned int data_setup_in_ns;
unsigned int data_setup_in_cycles;
unsigned int data_hold_in_cycles;
int ideal_sample_delay_in_ns;
unsigned int sample_delay_factor;
int tEYE;
unsigned int min_prop_delay_in_ns = DEF_MIN_PROP_DELAY;
unsigned int max_prop_delay_in_ns = DEF_MAX_PROP_DELAY;
/*
* If there are multiple chips, we need to relax the timings to allow
* for signal distortion due to higher capacitance.
*/
if (nand->numchips > 2) {
target.data_setup_in_ns += 10;
target.data_hold_in_ns += 10;
target.address_setup_in_ns += 10;
} else if (nand->numchips > 1) {
target.data_setup_in_ns += 5;
target.data_hold_in_ns += 5;
target.address_setup_in_ns += 5;
}
/* Check if improved timing information is available. */
improved_timing_is_available =
(target.tREA_in_ns >= 0) &&
(target.tRLOH_in_ns >= 0) &&
(target.tRHOH_in_ns >= 0);
/* Inspect the clock. */
nfc->clock_frequency_in_hz = clk_get_rate(r->clock[0]);
clock_frequency_in_hz = nfc->clock_frequency_in_hz;
clock_period_in_ns = NSEC_PER_SEC / clock_frequency_in_hz;
/*
* The NFC quantizes setup and hold parameters in terms of clock cycles.
* Here, we quantize the setup and hold timing parameters to the
* next-highest clock period to make sure we apply at least the
* specified times.
*
* For data setup and data hold, the hardware interprets a value of zero
* as the largest possible delay. This is not what's intended by a zero
* in the input parameter, so we impose a minimum of one cycle.
*/
data_setup_in_cycles = ns_to_cycles(target.data_setup_in_ns,
clock_period_in_ns, 1);
data_hold_in_cycles = ns_to_cycles(target.data_hold_in_ns,
clock_period_in_ns, 1);
address_setup_in_cycles = ns_to_cycles(target.address_setup_in_ns,
clock_period_in_ns, 0);
/*
* The clock's period affects the sample delay in a number of ways:
*
* (1) The NFC HAL tells us the maximum clock period the sample delay
* DLL can tolerate. If the clock period is greater than half that
* maximum, we must configure the DLL to be driven by half periods.
*
* (2) We need to convert from an ideal sample delay, in ns, to a
* "sample delay factor," which the NFC uses. This factor depends on
* whether we're driving the DLL with full or half periods.
* Paraphrasing the reference manual:
*
* AD = SDF x 0.125 x RP
*
* where:
*
* AD is the applied delay, in ns.
* SDF is the sample delay factor, which is dimensionless.
* RP is the reference period, in ns, which is a full clock period
* if the DLL is being driven by full periods, or half that if
* the DLL is being driven by half periods.
*
* Let's re-arrange this in a way that's more useful to us:
*
* 8
* SDF = AD x ----
* RP
*
* The reference period is either the clock period or half that, so this
* is:
*
* 8 AD x DDF
* SDF = AD x ----- = --------
* f x P P
*
* where:
*
* f is 1 or 1/2, depending on how we're driving the DLL.
* P is the clock period.
* DDF is the DLL Delay Factor, a dimensionless value that
* incorporates all the constants in the conversion.
*
* DDF will be either 8 or 16, both of which are powers of two. We can
* reduce the cost of this conversion by using bit shifts instead of
* multiplication or division. Thus:
*
* AD << DDS
* SDF = ---------
* P
*
* or
*
* AD = (SDF >> DDS) x P
*
* where:
*
* DDS is the DLL Delay Shift, the logarithm to base 2 of the DDF.
*/
if (clock_period_in_ns > (nfc->max_dll_clock_period_in_ns >> 1)) {
dll_use_half_periods = true;
dll_delay_shift = 3 + 1;
} else {
dll_use_half_periods = false;
dll_delay_shift = 3;
}
/*
* Compute the maximum sample delay the NFC allows, under current
* conditions. If the clock is running too slowly, no sample delay is
* possible.
*/
if (clock_period_in_ns > nfc->max_dll_clock_period_in_ns)
max_sample_delay_in_ns = 0;
else {
/*
* Compute the delay implied by the largest sample delay factor
* the NFC allows.
*/
max_sample_delay_in_ns =
(nfc->max_sample_delay_factor * clock_period_in_ns) >>
dll_delay_shift;
/*
* Check if the implied sample delay larger than the NFC
* actually allows.
*/
if (max_sample_delay_in_ns > nfc->max_dll_delay_in_ns)
max_sample_delay_in_ns = nfc->max_dll_delay_in_ns;
}
/*
* Check if improved timing information is available. If not, we have to
* use a less-sophisticated algorithm.
*/
if (!improved_timing_is_available) {
/*
* Fold the read setup time required by the NFC into the ideal
* sample delay.
*/
ideal_sample_delay_in_ns = target.gpmi_sample_delay_in_ns +
nfc->internal_data_setup_in_ns;
/*
* The ideal sample delay may be greater than the maximum
* allowed by the NFC. If so, we can trade off sample delay time
* for more data setup time.
*
* In each iteration of the following loop, we add a cycle to
* the data setup time and subtract a corresponding amount from
* the sample delay until we've satisified the constraints or
* can't do any better.
*/
while ((ideal_sample_delay_in_ns > max_sample_delay_in_ns) &&
(data_setup_in_cycles < nfc->max_data_setup_cycles)) {
data_setup_in_cycles++;
ideal_sample_delay_in_ns -= clock_period_in_ns;
if (ideal_sample_delay_in_ns < 0)
ideal_sample_delay_in_ns = 0;
}
/*
* Compute the sample delay factor that corresponds most closely
* to the ideal sample delay. If the result is too large for the
* NFC, use the maximum value.
*
* Notice that we use the ns_to_cycles function to compute the
* sample delay factor. We do this because the form of the
* computation is the same as that for calculating cycles.
*/
sample_delay_factor =
ns_to_cycles(
ideal_sample_delay_in_ns << dll_delay_shift,
clock_period_in_ns, 0);
if (sample_delay_factor > nfc->max_sample_delay_factor)
sample_delay_factor = nfc->max_sample_delay_factor;
/* Skip to the part where we return our results. */
goto return_results;
}
/*
* If control arrives here, we have more detailed timing information,
* so we can use a better algorithm.
*/
/*
* Fold the read setup time required by the NFC into the maximum
* propagation delay.
*/
max_prop_delay_in_ns += nfc->internal_data_setup_in_ns;
/*
* Earlier, we computed the number of clock cycles required to satisfy
* the data setup time. Now, we need to know the actual nanoseconds.
*/
data_setup_in_ns = clock_period_in_ns * data_setup_in_cycles;
/*
* Compute tEYE, the width of the data eye when reading from the NAND
* Flash. The eye width is fundamentally determined by the data setup
* time, perturbed by propagation delays and some characteristics of the
* NAND Flash device.
*
* start of the eye = max_prop_delay + tREA
* end of the eye = min_prop_delay + tRHOH + data_setup
*/
tEYE = (int)min_prop_delay_in_ns + (int)target.tRHOH_in_ns +
(int)data_setup_in_ns;
tEYE -= (int)max_prop_delay_in_ns + (int)target.tREA_in_ns;
/*
* The eye must be open. If it's not, we can try to open it by
* increasing its main forcer, the data setup time.
*
* In each iteration of the following loop, we increase the data setup
* time by a single clock cycle. We do this until either the eye is
* open or we run into NFC limits.
*/
while ((tEYE <= 0) &&
(data_setup_in_cycles < nfc->max_data_setup_cycles)) {
/* Give a cycle to data setup. */
data_setup_in_cycles++;
/* Synchronize the data setup time with the cycles. */
data_setup_in_ns += clock_period_in_ns;
/* Adjust tEYE accordingly. */
tEYE += clock_period_in_ns;
}
/*
* When control arrives here, the eye is open. The ideal time to sample
* the data is in the center of the eye:
*
* end of the eye + start of the eye
* --------------------------------- - data_setup
* 2
*
* After some algebra, this simplifies to the code immediately below.
*/
ideal_sample_delay_in_ns =
((int)max_prop_delay_in_ns +
(int)target.tREA_in_ns +
(int)min_prop_delay_in_ns +
(int)target.tRHOH_in_ns -
(int)data_setup_in_ns) >> 1;
/*
* The following figure illustrates some aspects of a NAND Flash read:
*
*
* __ _____________________________________
* RDN \_________________/
*
* <---- tEYE ----->
* /-----------------\
* Read Data ----------------------------< >---------
* \-----------------/
* ^ ^ ^ ^
* | | | |
* |<--Data Setup -->|<--Delay Time -->| |
* | | | |
* | | |
* | |<-- Quantized Delay Time -->|
* | | |
*
*
* We have some issues we must now address:
*
* (1) The *ideal* sample delay time must not be negative. If it is, we
* jam it to zero.
*
* (2) The *ideal* sample delay time must not be greater than that
* allowed by the NFC. If it is, we can increase the data setup
* time, which will reduce the delay between the end of the data
* setup and the center of the eye. It will also make the eye
* larger, which might help with the next issue...
*
* (3) The *quantized* sample delay time must not fall either before the
* eye opens or after it closes (the latter is the problem
* illustrated in the above figure).
*/
/* Jam a negative ideal sample delay to zero. */
if (ideal_sample_delay_in_ns < 0)
ideal_sample_delay_in_ns = 0;
/*
* Extend the data setup as needed to reduce the ideal sample delay
* below the maximum permitted by the NFC.
*/
while ((ideal_sample_delay_in_ns > max_sample_delay_in_ns) &&
(data_setup_in_cycles < nfc->max_data_setup_cycles)) {
/* Give a cycle to data setup. */
data_setup_in_cycles++;
/* Synchronize the data setup time with the cycles. */
data_setup_in_ns += clock_period_in_ns;
/* Adjust tEYE accordingly. */
tEYE += clock_period_in_ns;
/*
* Decrease the ideal sample delay by one half cycle, to keep it
* in the middle of the eye.
*/
ideal_sample_delay_in_ns -= (clock_period_in_ns >> 1);
/* Jam a negative ideal sample delay to zero. */
if (ideal_sample_delay_in_ns < 0)
ideal_sample_delay_in_ns = 0;
}
/*
* Compute the sample delay factor that corresponds to the ideal sample
* delay. If the result is too large, then use the maximum allowed
* value.
*
* Notice that we use the ns_to_cycles function to compute the sample
* delay factor. We do this because the form of the computation is the
* same as that for calculating cycles.
*/
sample_delay_factor =
ns_to_cycles(ideal_sample_delay_in_ns << dll_delay_shift,
clock_period_in_ns, 0);
if (sample_delay_factor > nfc->max_sample_delay_factor)
sample_delay_factor = nfc->max_sample_delay_factor;
/*
* These macros conveniently encapsulate a computation we'll use to
* continuously evaluate whether or not the data sample delay is inside
* the eye.
*/
#define IDEAL_DELAY ((int) ideal_sample_delay_in_ns)
#define QUANTIZED_DELAY \
((int) ((sample_delay_factor * clock_period_in_ns) >> \
dll_delay_shift))
#define DELAY_ERROR (abs(QUANTIZED_DELAY - IDEAL_DELAY))
#define SAMPLE_IS_NOT_WITHIN_THE_EYE (DELAY_ERROR > (tEYE >> 1))
/*
* While the quantized sample time falls outside the eye, reduce the
* sample delay or extend the data setup to move the sampling point back
* toward the eye. Do not allow the number of data setup cycles to
* exceed the maximum allowed by the NFC.
*/
while (SAMPLE_IS_NOT_WITHIN_THE_EYE &&
(data_setup_in_cycles < nfc->max_data_setup_cycles)) {
/*
* If control arrives here, the quantized sample delay falls
* outside the eye. Check if it's before the eye opens, or after
* the eye closes.
*/
if (QUANTIZED_DELAY > IDEAL_DELAY) {
/*
* If control arrives here, the quantized sample delay
* falls after the eye closes. Decrease the quantized
* delay time and then go back to re-evaluate.
*/
if (sample_delay_factor != 0)
sample_delay_factor--;
continue;
}
/*
* If control arrives here, the quantized sample delay falls
* before the eye opens. Shift the sample point by increasing
* data setup time. This will also make the eye larger.
*/
/* Give a cycle to data setup. */
data_setup_in_cycles++;
/* Synchronize the data setup time with the cycles. */
data_setup_in_ns += clock_period_in_ns;
/* Adjust tEYE accordingly. */
tEYE += clock_period_in_ns;
/*
* Decrease the ideal sample delay by one half cycle, to keep it
* in the middle of the eye.
*/
ideal_sample_delay_in_ns -= (clock_period_in_ns >> 1);
/* ...and one less period for the delay time. */
ideal_sample_delay_in_ns -= clock_period_in_ns;
/* Jam a negative ideal sample delay to zero. */
if (ideal_sample_delay_in_ns < 0)
ideal_sample_delay_in_ns = 0;
/*
* We have a new ideal sample delay, so re-compute the quantized
* delay.
*/
sample_delay_factor =
ns_to_cycles(
ideal_sample_delay_in_ns << dll_delay_shift,
clock_period_in_ns, 0);
if (sample_delay_factor > nfc->max_sample_delay_factor)
sample_delay_factor = nfc->max_sample_delay_factor;
}
/* Control arrives here when we're ready to return our results. */
return_results:
hw->data_setup_in_cycles = data_setup_in_cycles;
hw->data_hold_in_cycles = data_hold_in_cycles;
hw->address_setup_in_cycles = address_setup_in_cycles;
hw->use_half_periods = dll_use_half_periods;
hw->sample_delay_factor = sample_delay_factor;
hw->device_busy_timeout = GPMI_DEFAULT_BUSY_TIMEOUT;
hw->wrn_dly_sel = BV_GPMI_CTRL1_WRN_DLY_SEL_4_TO_8NS;
/* Return success. */
return 0;
}
/*
* <1> Firstly, we should know what's the GPMI-clock means.
* The GPMI-clock is the internal clock in the gpmi nand controller.
* If you set 100MHz to gpmi nand controller, the GPMI-clock's period
* is 10ns. Mark the GPMI-clock's period as GPMI-clock-period.
*
* <2> Secondly, we should know what's the frequency on the nand chip pins.
* The frequency on the nand chip pins is derived from the GPMI-clock.
* We can get it from the following equation:
*
* F = G / (DS + DH)
*
* F : the frequency on the nand chip pins.
* G : the GPMI clock, such as 100MHz.
* DS : GPMI_HW_GPMI_TIMING0:DATA_SETUP
* DH : GPMI_HW_GPMI_TIMING0:DATA_HOLD
*
* <3> Thirdly, when the frequency on the nand chip pins is above 33MHz,
* the nand EDO(extended Data Out) timing could be applied.
* The GPMI implements a feedback read strobe to sample the read data.
* The feedback read strobe can be delayed to support the nand EDO timing
* where the read strobe may deasserts before the read data is valid, and
* read data is valid for some time after read strobe.
*
* The following figure illustrates some aspects of a NAND Flash read:
*
* |<---tREA---->|
* | |
* | | |
* |<--tRP-->| |
* | | |
* __ ___|__________________________________
* RDN \________/ |
* |
* /---------\
* Read Data --------------< >---------
* \---------/
* | |
* |<-D->|
* FeedbackRDN ________ ____________
* \___________/
*
* D stands for delay, set in the HW_GPMI_CTRL1:RDN_DELAY.
*
*
* <4> Now, we begin to describe how to compute the right RDN_DELAY.
*
* 4.1) From the aspect of the nand chip pins:
* Delay = (tREA + C - tRP) {1}
*
* tREA : the maximum read access time. From the ONFI nand standards,
* we know that tREA is 16ns in mode 5, tREA is 20ns is mode 4.
* Please check it in : www.onfi.org
* C : a constant for adjust the delay. default is 4.
* tRP : the read pulse width.
* Specified by the HW_GPMI_TIMING0:DATA_SETUP:
* tRP = (GPMI-clock-period) * DATA_SETUP
*
* 4.2) From the aspect of the GPMI nand controller:
* Delay = RDN_DELAY * 0.125 * RP {2}
*
* RP : the DLL reference period.
* if (GPMI-clock-period > DLL_THRETHOLD)
* RP = GPMI-clock-period / 2;
* else
* RP = GPMI-clock-period;
*
* Set the HW_GPMI_CTRL1:HALF_PERIOD if GPMI-clock-period
* is greater DLL_THRETHOLD. In other SOCs, the DLL_THRETHOLD
* is 16ns, but in mx6q, we use 12ns.
*
* 4.3) since {1} equals {2}, we get:
*
* (tREA + 4 - tRP) * 8
* RDN_DELAY = --------------------- {3}
* RP
*
* 4.4) We only support the fastest asynchronous mode of ONFI nand.
* For some ONFI nand, the mode 4 is the fastest mode;
* while for some ONFI nand, the mode 5 is the fastest mode.
* So we only support the mode 4 and mode 5. It is no need to
* support other modes.
*/
static void gpmi_compute_edo_timing(struct gpmi_nand_data *this,
struct gpmi_nfc_hardware_timing *hw)
{
struct resources *r = &this->resources;
unsigned long rate = clk_get_rate(r->clock[0]);
int mode = this->timing_mode;
int dll_threshold = this->devdata->max_chain_delay;
unsigned long delay;
unsigned long clk_period;
int t_rea;
int c = 4;
int t_rp;
int rp;
/*
* [1] for GPMI_HW_GPMI_TIMING0:
* The async mode requires 40MHz for mode 4, 50MHz for mode 5.
* The GPMI can support 100MHz at most. So if we want to
* get the 40MHz or 50MHz, we have to set DS=1, DH=1.
* Set the ADDRESS_SETUP to 0 in mode 4.
*/
hw->data_setup_in_cycles = 1;
hw->data_hold_in_cycles = 1;
hw->address_setup_in_cycles = ((mode == 5) ? 1 : 0);
/* [2] for GPMI_HW_GPMI_TIMING1 */
hw->device_busy_timeout = 0x9000;
/* [3] for GPMI_HW_GPMI_CTRL1 */
hw->wrn_dly_sel = BV_GPMI_CTRL1_WRN_DLY_SEL_NO_DELAY;
/*
* Enlarge 10 times for the numerator and denominator in {3}.
* This make us to get more accurate result.
*/
clk_period = NSEC_PER_SEC / (rate / 10);
dll_threshold *= 10;
t_rea = ((mode == 5) ? 16 : 20) * 10;
c *= 10;
t_rp = clk_period * 1; /* DATA_SETUP is 1 */
if (clk_period > dll_threshold) {
hw->use_half_periods = 1;
rp = clk_period / 2;
} else {
hw->use_half_periods = 0;
rp = clk_period;
}
/*
* Multiply the numerator with 10, we could do a round off:
* 7.8 round up to 8; 7.4 round down to 7.
*/
delay = (((t_rea + c - t_rp) * 8) * 10) / rp;
delay = (delay + 5) / 10;
hw->sample_delay_factor = delay;
}
static int enable_edo_mode(struct gpmi_nand_data *this, int mode)
{
struct resources *r = &this->resources;
struct nand_chip *nand = &this->nand;
struct mtd_info *mtd = &this->mtd;
uint8_t *feature;
unsigned long rate;
int ret;
feature = kzalloc(ONFI_SUBFEATURE_PARAM_LEN, GFP_KERNEL);
if (!feature)
return -ENOMEM;
nand->select_chip(mtd, 0);
/* [1] send SET FEATURE commond to NAND */
feature[0] = mode;
ret = nand->onfi_set_features(mtd, nand,
ONFI_FEATURE_ADDR_TIMING_MODE, feature);
if (ret)
goto err_out;
/* [2] send GET FEATURE command to double-check the timing mode */
memset(feature, 0, ONFI_SUBFEATURE_PARAM_LEN);
ret = nand->onfi_get_features(mtd, nand,
ONFI_FEATURE_ADDR_TIMING_MODE, feature);
if (ret || feature[0] != mode)
goto err_out;
nand->select_chip(mtd, -1);
/* [3] set the main IO clock, 100MHz for mode 5, 80MHz for mode 4. */
rate = (mode == 5) ? 100000000 : 80000000;
clk_set_rate(r->clock[0], rate);
/* Let the gpmi_begin() re-compute the timing again. */
this->flags &= ~GPMI_TIMING_INIT_OK;
this->flags |= GPMI_ASYNC_EDO_ENABLED;
this->timing_mode = mode;
kfree(feature);
dev_info(this->dev, "enable the asynchronous EDO mode %d\n", mode);
return 0;
err_out:
nand->select_chip(mtd, -1);
kfree(feature);
dev_err(this->dev, "mode:%d ,failed in set feature.\n", mode);
return -EINVAL;
}
int gpmi_extra_init(struct gpmi_nand_data *this)
{
struct nand_chip *chip = &this->nand;
/* Enable the asynchronous EDO feature. */
if (GPMI_IS_MX6(this) && chip->onfi_version) {
int mode = onfi_get_async_timing_mode(chip);
/* We only support the timing mode 4 and mode 5. */
if (mode & ONFI_TIMING_MODE_5)
mode = 5;
else if (mode & ONFI_TIMING_MODE_4)
mode = 4;
else
return 0;
return enable_edo_mode(this, mode);
}
return 0;
}
/* Begin the I/O */
void gpmi_begin(struct gpmi_nand_data *this)
{
struct resources *r = &this->resources;
void __iomem *gpmi_regs = r->gpmi_regs;
unsigned int clock_period_in_ns;
uint32_t reg;
unsigned int dll_wait_time_in_us;
struct gpmi_nfc_hardware_timing hw;
int ret;
/* Enable the clock. */
ret = gpmi_enable_clk(this);
if (ret) {
dev_err(this->dev, "We failed in enable the clk\n");
goto err_out;
}
/* Only initialize the timing once */
if (this->flags & GPMI_TIMING_INIT_OK)
return;
this->flags |= GPMI_TIMING_INIT_OK;
if (this->flags & GPMI_ASYNC_EDO_ENABLED)
gpmi_compute_edo_timing(this, &hw);
else
gpmi_nfc_compute_hardware_timing(this, &hw);
/* [1] Set HW_GPMI_TIMING0 */
reg = BF_GPMI_TIMING0_ADDRESS_SETUP(hw.address_setup_in_cycles) |
BF_GPMI_TIMING0_DATA_HOLD(hw.data_hold_in_cycles) |
BF_GPMI_TIMING0_DATA_SETUP(hw.data_setup_in_cycles);
writel(reg, gpmi_regs + HW_GPMI_TIMING0);
/* [2] Set HW_GPMI_TIMING1 */
writel(BF_GPMI_TIMING1_BUSY_TIMEOUT(hw.device_busy_timeout),
gpmi_regs + HW_GPMI_TIMING1);
/* [3] The following code is to set the HW_GPMI_CTRL1. */
/* Set the WRN_DLY_SEL */
writel(BM_GPMI_CTRL1_WRN_DLY_SEL, gpmi_regs + HW_GPMI_CTRL1_CLR);
writel(BF_GPMI_CTRL1_WRN_DLY_SEL(hw.wrn_dly_sel),
gpmi_regs + HW_GPMI_CTRL1_SET);
/* DLL_ENABLE must be set to 0 when setting RDN_DELAY or HALF_PERIOD. */
writel(BM_GPMI_CTRL1_DLL_ENABLE, gpmi_regs + HW_GPMI_CTRL1_CLR);
/* Clear out the DLL control fields. */
reg = BM_GPMI_CTRL1_RDN_DELAY | BM_GPMI_CTRL1_HALF_PERIOD;
writel(reg, gpmi_regs + HW_GPMI_CTRL1_CLR);
/* If no sample delay is called for, return immediately. */
if (!hw.sample_delay_factor)
return;
/* Set RDN_DELAY or HALF_PERIOD. */
reg = ((hw.use_half_periods) ? BM_GPMI_CTRL1_HALF_PERIOD : 0)
| BF_GPMI_CTRL1_RDN_DELAY(hw.sample_delay_factor);
writel(reg, gpmi_regs + HW_GPMI_CTRL1_SET);
/* At last, we enable the DLL. */
writel(BM_GPMI_CTRL1_DLL_ENABLE, gpmi_regs + HW_GPMI_CTRL1_SET);
/*
* After we enable the GPMI DLL, we have to wait 64 clock cycles before
* we can use the GPMI. Calculate the amount of time we need to wait,
* in microseconds.
*/
clock_period_in_ns = NSEC_PER_SEC / clk_get_rate(r->clock[0]);
dll_wait_time_in_us = (clock_period_in_ns * 64) / 1000;
if (!dll_wait_time_in_us)
dll_wait_time_in_us = 1;
/* Wait for the DLL to settle. */
udelay(dll_wait_time_in_us);
err_out:
return;
}
void gpmi_end(struct gpmi_nand_data *this)
{
gpmi_disable_clk(this);
}
/* Clears a BCH interrupt. */
void gpmi_clear_bch(struct gpmi_nand_data *this)
{
struct resources *r = &this->resources;
writel(BM_BCH_CTRL_COMPLETE_IRQ, r->bch_regs + HW_BCH_CTRL_CLR);
}
/* Returns the Ready/Busy status of the given chip. */
int gpmi_is_ready(struct gpmi_nand_data *this, unsigned chip)
{
struct resources *r = &this->resources;
uint32_t mask = 0;
uint32_t reg = 0;
if (GPMI_IS_MX23(this)) {
mask = MX23_BM_GPMI_DEBUG_READY0 << chip;
reg = readl(r->gpmi_regs + HW_GPMI_DEBUG);
} else if (GPMI_IS_MX28(this) || GPMI_IS_MX6(this)) {
/*
* In the imx6, all the ready/busy pins are bound
* together. So we only need to check chip 0.
*/
if (GPMI_IS_MX6(this))
chip = 0;
/* MX28 shares the same R/B register as MX6Q. */
mask = MX28_BF_GPMI_STAT_READY_BUSY(1 << chip);
reg = readl(r->gpmi_regs + HW_GPMI_STAT);
} else
dev_err(this->dev, "unknown arch.\n");
return reg & mask;
}
static inline void set_dma_type(struct gpmi_nand_data *this,
enum dma_ops_type type)
{
this->last_dma_type = this->dma_type;
this->dma_type = type;
}
int gpmi_send_command(struct gpmi_nand_data *this)
{
struct dma_chan *channel = get_dma_chan(this);
struct dma_async_tx_descriptor *desc;
struct scatterlist *sgl;
int chip = this->current_chip;
u32 pio[3];
/* [1] send out the PIO words */
pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(BV_GPMI_CTRL0_COMMAND_MODE__WRITE)
| BM_GPMI_CTRL0_WORD_LENGTH
| BF_GPMI_CTRL0_CS(chip, this)
| BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
| BF_GPMI_CTRL0_ADDRESS(BV_GPMI_CTRL0_ADDRESS__NAND_CLE)
| BM_GPMI_CTRL0_ADDRESS_INCREMENT
| BF_GPMI_CTRL0_XFER_COUNT(this->command_length);
pio[1] = pio[2] = 0;
desc = dmaengine_prep_slave_sg(channel,
(struct scatterlist *)pio,
ARRAY_SIZE(pio), DMA_TRANS_NONE, 0);
if (!desc)
return -EINVAL;
/* [2] send out the COMMAND + ADDRESS string stored in @buffer */
sgl = &this->cmd_sgl;
sg_init_one(sgl, this->cmd_buffer, this->command_length);
dma_map_sg(this->dev, sgl, 1, DMA_TO_DEVICE);
desc = dmaengine_prep_slave_sg(channel,
sgl, 1, DMA_MEM_TO_DEV,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc)
return -EINVAL;
/* [3] submit the DMA */
set_dma_type(this, DMA_FOR_COMMAND);
return start_dma_without_bch_irq(this, desc);
}
int gpmi_send_data(struct gpmi_nand_data *this)
{
struct dma_async_tx_descriptor *desc;
struct dma_chan *channel = get_dma_chan(this);
int chip = this->current_chip;
uint32_t command_mode;
uint32_t address;
u32 pio[2];
/* [1] PIO */
command_mode = BV_GPMI_CTRL0_COMMAND_MODE__WRITE;
address = BV_GPMI_CTRL0_ADDRESS__NAND_DATA;
pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(command_mode)
| BM_GPMI_CTRL0_WORD_LENGTH
| BF_GPMI_CTRL0_CS(chip, this)
| BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
| BF_GPMI_CTRL0_ADDRESS(address)
| BF_GPMI_CTRL0_XFER_COUNT(this->upper_len);
pio[1] = 0;
desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)pio,
ARRAY_SIZE(pio), DMA_TRANS_NONE, 0);
if (!desc)
return -EINVAL;
/* [2] send DMA request */
prepare_data_dma(this, DMA_TO_DEVICE);
desc = dmaengine_prep_slave_sg(channel, &this->data_sgl,
1, DMA_MEM_TO_DEV,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc)
return -EINVAL;
/* [3] submit the DMA */
set_dma_type(this, DMA_FOR_WRITE_DATA);
return start_dma_without_bch_irq(this, desc);
}
int gpmi_read_data(struct gpmi_nand_data *this)
{
struct dma_async_tx_descriptor *desc;
struct dma_chan *channel = get_dma_chan(this);
int chip = this->current_chip;
u32 pio[2];
/* [1] : send PIO */
pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(BV_GPMI_CTRL0_COMMAND_MODE__READ)
| BM_GPMI_CTRL0_WORD_LENGTH
| BF_GPMI_CTRL0_CS(chip, this)
| BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
| BF_GPMI_CTRL0_ADDRESS(BV_GPMI_CTRL0_ADDRESS__NAND_DATA)
| BF_GPMI_CTRL0_XFER_COUNT(this->upper_len);
pio[1] = 0;
desc = dmaengine_prep_slave_sg(channel,
(struct scatterlist *)pio,
ARRAY_SIZE(pio), DMA_TRANS_NONE, 0);
if (!desc)
return -EINVAL;
/* [2] : send DMA request */
prepare_data_dma(this, DMA_FROM_DEVICE);
desc = dmaengine_prep_slave_sg(channel, &this->data_sgl,
1, DMA_DEV_TO_MEM,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc)
return -EINVAL;
/* [3] : submit the DMA */
set_dma_type(this, DMA_FOR_READ_DATA);
return start_dma_without_bch_irq(this, desc);
}
int gpmi_send_page(struct gpmi_nand_data *this,
dma_addr_t payload, dma_addr_t auxiliary)
{
struct bch_geometry *geo = &this->bch_geometry;
uint32_t command_mode;
uint32_t address;
uint32_t ecc_command;
uint32_t buffer_mask;
struct dma_async_tx_descriptor *desc;
struct dma_chan *channel = get_dma_chan(this);
int chip = this->current_chip;
u32 pio[6];
/* A DMA descriptor that does an ECC page read. */
command_mode = BV_GPMI_CTRL0_COMMAND_MODE__WRITE;
address = BV_GPMI_CTRL0_ADDRESS__NAND_DATA;
ecc_command = BV_GPMI_ECCCTRL_ECC_CMD__BCH_ENCODE;
buffer_mask = BV_GPMI_ECCCTRL_BUFFER_MASK__BCH_PAGE |
BV_GPMI_ECCCTRL_BUFFER_MASK__BCH_AUXONLY;
pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(command_mode)
| BM_GPMI_CTRL0_WORD_LENGTH
| BF_GPMI_CTRL0_CS(chip, this)
| BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
| BF_GPMI_CTRL0_ADDRESS(address)
| BF_GPMI_CTRL0_XFER_COUNT(0);
pio[1] = 0;
pio[2] = BM_GPMI_ECCCTRL_ENABLE_ECC
| BF_GPMI_ECCCTRL_ECC_CMD(ecc_command)
| BF_GPMI_ECCCTRL_BUFFER_MASK(buffer_mask);
pio[3] = geo->page_size;
pio[4] = payload;
pio[5] = auxiliary;
desc = dmaengine_prep_slave_sg(channel,
(struct scatterlist *)pio,
ARRAY_SIZE(pio), DMA_TRANS_NONE,
DMA_CTRL_ACK);
if (!desc)
return -EINVAL;
set_dma_type(this, DMA_FOR_WRITE_ECC_PAGE);
return start_dma_with_bch_irq(this, desc);
}
int gpmi_read_page(struct gpmi_nand_data *this,
dma_addr_t payload, dma_addr_t auxiliary)
{
struct bch_geometry *geo = &this->bch_geometry;
uint32_t command_mode;
uint32_t address;
uint32_t ecc_command;
uint32_t buffer_mask;
struct dma_async_tx_descriptor *desc;
struct dma_chan *channel = get_dma_chan(this);
int chip = this->current_chip;
u32 pio[6];
/* [1] Wait for the chip to report ready. */
command_mode = BV_GPMI_CTRL0_COMMAND_MODE__WAIT_FOR_READY;
address = BV_GPMI_CTRL0_ADDRESS__NAND_DATA;
pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(command_mode)
| BM_GPMI_CTRL0_WORD_LENGTH
| BF_GPMI_CTRL0_CS(chip, this)
| BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
| BF_GPMI_CTRL0_ADDRESS(address)
| BF_GPMI_CTRL0_XFER_COUNT(0);
pio[1] = 0;
desc = dmaengine_prep_slave_sg(channel,
(struct scatterlist *)pio, 2,
DMA_TRANS_NONE, 0);
if (!desc)
return -EINVAL;
/* [2] Enable the BCH block and read. */
command_mode = BV_GPMI_CTRL0_COMMAND_MODE__READ;
address = BV_GPMI_CTRL0_ADDRESS__NAND_DATA;
ecc_command = BV_GPMI_ECCCTRL_ECC_CMD__BCH_DECODE;
buffer_mask = BV_GPMI_ECCCTRL_BUFFER_MASK__BCH_PAGE
| BV_GPMI_ECCCTRL_BUFFER_MASK__BCH_AUXONLY;
pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(command_mode)
| BM_GPMI_CTRL0_WORD_LENGTH
| BF_GPMI_CTRL0_CS(chip, this)
| BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
| BF_GPMI_CTRL0_ADDRESS(address)
| BF_GPMI_CTRL0_XFER_COUNT(geo->page_size);
pio[1] = 0;
pio[2] = BM_GPMI_ECCCTRL_ENABLE_ECC
| BF_GPMI_ECCCTRL_ECC_CMD(ecc_command)
| BF_GPMI_ECCCTRL_BUFFER_MASK(buffer_mask);
pio[3] = geo->page_size;
pio[4] = payload;
pio[5] = auxiliary;
desc = dmaengine_prep_slave_sg(channel,
(struct scatterlist *)pio,
ARRAY_SIZE(pio), DMA_TRANS_NONE,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc)
return -EINVAL;
/* [3] Disable the BCH block */
command_mode = BV_GPMI_CTRL0_COMMAND_MODE__WAIT_FOR_READY;
address = BV_GPMI_CTRL0_ADDRESS__NAND_DATA;
pio[0] = BF_GPMI_CTRL0_COMMAND_MODE(command_mode)
| BM_GPMI_CTRL0_WORD_LENGTH
| BF_GPMI_CTRL0_CS(chip, this)
| BF_GPMI_CTRL0_LOCK_CS(LOCK_CS_ENABLE, this)
| BF_GPMI_CTRL0_ADDRESS(address)
| BF_GPMI_CTRL0_XFER_COUNT(geo->page_size);
pio[1] = 0;
pio[2] = 0; /* clear GPMI_HW_GPMI_ECCCTRL, disable the BCH. */
desc = dmaengine_prep_slave_sg(channel,
(struct scatterlist *)pio, 3,
DMA_TRANS_NONE,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc)
return -EINVAL;
/* [4] submit the DMA */
set_dma_type(this, DMA_FOR_READ_ECC_PAGE);
return start_dma_with_bch_irq(this, desc);
}
/**
* gpmi_copy_bits - copy bits from one memory region to another
* @dst: destination buffer
* @dst_bit_off: bit offset we're starting to write at
* @src: source buffer
* @src_bit_off: bit offset we're starting to read from
* @nbits: number of bits to copy
*
* This functions copies bits from one memory region to another, and is used by
* the GPMI driver to copy ECC sections which are not guaranteed to be byte
* aligned.
*
* src and dst should not overlap.
*
*/
void gpmi_copy_bits(u8 *dst, size_t dst_bit_off,
const u8 *src, size_t src_bit_off,
size_t nbits)
{
size_t i;
size_t nbytes;
u32 src_buffer = 0;
size_t bits_in_src_buffer = 0;
if (!nbits)
return;
/*
* Move src and dst pointers to the closest byte pointer and store bit
* offsets within a byte.
*/
src += src_bit_off / 8;
src_bit_off %= 8;
dst += dst_bit_off / 8;
dst_bit_off %= 8;
/*
* Initialize the src_buffer value with bits available in the first
* byte of data so that we end up with a byte aligned src pointer.
*/
if (src_bit_off) {
src_buffer = src[0] >> src_bit_off;
if (nbits >= (8 - src_bit_off)) {
bits_in_src_buffer += 8 - src_bit_off;
} else {
src_buffer &= GENMASK(nbits - 1, 0);
bits_in_src_buffer += nbits;
}
nbits -= bits_in_src_buffer;
src++;
}
/* Calculate the number of bytes that can be copied from src to dst. */
nbytes = nbits / 8;
/* Try to align dst to a byte boundary. */
if (dst_bit_off) {
if (bits_in_src_buffer < (8 - dst_bit_off) && nbytes) {
src_buffer |= src[0] << bits_in_src_buffer;
bits_in_src_buffer += 8;
src++;
nbytes--;
}
if (bits_in_src_buffer >= (8 - dst_bit_off)) {
dst[0] &= GENMASK(dst_bit_off - 1, 0);
dst[0] |= src_buffer << dst_bit_off;
src_buffer >>= (8 - dst_bit_off);
bits_in_src_buffer -= (8 - dst_bit_off);
dst_bit_off = 0;
dst++;
if (bits_in_src_buffer > 7) {
bits_in_src_buffer -= 8;
dst[0] = src_buffer;
dst++;
src_buffer >>= 8;
}
}
}
if (!bits_in_src_buffer && !dst_bit_off) {
/*
* Both src and dst pointers are byte aligned, thus we can
* just use the optimized memcpy function.
*/
if (nbytes)
memcpy(dst, src, nbytes);
} else {
/*
* src buffer is not byte aligned, hence we have to copy each
* src byte to the src_buffer variable before extracting a byte
* to store in dst.
*/
for (i = 0; i < nbytes; i++) {
src_buffer |= src[i] << bits_in_src_buffer;
dst[i] = src_buffer;
src_buffer >>= 8;
}
}
/* Update dst and src pointers */
dst += nbytes;
src += nbytes;
/*
* nbits is the number of remaining bits. It should not exceed 8 as
* we've already copied as much bytes as possible.
*/
nbits %= 8;
/*
* If there's no more bits to copy to the destination and src buffer
* was already byte aligned, then we're done.
*/
if (!nbits && !bits_in_src_buffer)
return;
/* Copy the remaining bits to src_buffer */
if (nbits)
src_buffer |= (*src & GENMASK(nbits - 1, 0)) <<
bits_in_src_buffer;
bits_in_src_buffer += nbits;
/*
* In case there were not enough bits to get a byte aligned dst buffer
* prepare the src_buffer variable to match the dst organization (shift
* src_buffer by dst_bit_off and retrieve the least significant bits
* from dst).
*/
if (dst_bit_off)
src_buffer = (src_buffer << dst_bit_off) |
(*dst & GENMASK(dst_bit_off - 1, 0));
bits_in_src_buffer += dst_bit_off;
/*
* Keep most significant bits from dst if we end up with an unaligned
* number of bits.
*/
nbytes = bits_in_src_buffer / 8;
if (bits_in_src_buffer % 8) {
src_buffer |= (dst[nbytes] &
GENMASK(7, bits_in_src_buffer % 8)) <<
(nbytes * 8);
nbytes++;
}
/* Copy the remaining bytes to dst */
for (i = 0; i < nbytes; i++) {
dst[i] = src_buffer;
src_buffer >>= 8;
}
}