/*
* drivers/mtd/maps/gpio-addr-flash.c
*
* Handle the case where a flash device is mostly addressed using physical
* line and supplemented by GPIOs. This way you can hook up say a 8MiB flash
* to a 2MiB memory range and use the GPIOs to select a particular range.
*
* Copyright © 2000 Nicolas Pitre <nico@cam.org>
* Copyright © 2005-2009 Analog Devices Inc.
*
* Enter bugs at http://blackfin.uclinux.org/
*
* Licensed under the GPL-2 or later.
*/
#include <linux/gpio.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/map.h>
#include <linux/mtd/partitions.h>
#include <linux/mtd/physmap.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/types.h>
#define pr_devinit(fmt, args...) \
({ static const char __fmt[] = fmt; printk(__fmt, ## args); })
#define DRIVER_NAME "gpio-addr-flash"
#define PFX DRIVER_NAME ": "
/**
* struct async_state - keep GPIO flash state
* @mtd: MTD state for this mapping
* @map: MTD map state for this flash
* @gpio_count: number of GPIOs used to address
* @gpio_addrs: array of GPIOs to twiddle
* @gpio_values: cached GPIO values
* @win_size: dedicated memory size (if no GPIOs)
*/
struct async_state {
struct mtd_info *mtd;
struct map_info map;
size_t gpio_count;
unsigned *gpio_addrs;
int *gpio_values;
unsigned long win_size;
};
#define gf_map_info_to_state(mi) ((struct async_state *)(mi)->map_priv_1)
/**
* gf_set_gpios() - set GPIO address lines to access specified flash offset
* @state: GPIO flash state
* @ofs: desired offset to access
*
* Rather than call the GPIO framework every time, cache the last-programmed
* value. This speeds up sequential accesses (which are by far the most common
* type). We rely on the GPIO framework to treat non-zero value as high so
* that we don't have to normalize the bits.
*/
static void gf_set_gpios(struct async_state *state, unsigned long ofs)
{
size_t i = 0;
int value;
ofs /= state->win_size;
do {
value = ofs & (1 << i);
if (state->gpio_values[i] != value) {
gpio_set_value(state->gpio_addrs[i], value);
state->gpio_values[i] = value;
}
} while (++i < state->gpio_count);
}
/**
* gf_read() - read a word at the specified offset
* @map: MTD map state
* @ofs: desired offset to read
*/
static map_word gf_read(struct map_info *map, unsigned long ofs)
{
struct async_state *state = gf_map_info_to_state(map);
uint16_t word;
map_word test;
gf_set_gpios(state, ofs);
word = readw(map->virt + (ofs % state->win_size));
test.x[0] = word;
return test;
}
/**
* gf_copy_from() - copy a chunk of data from the flash
* @map: MTD map state
* @to: memory to copy to
* @from: flash offset to copy from
* @len: how much to copy
*
* We rely on the MTD layer to chunk up copies such that a single request here
* will not cross a window size. This allows us to only wiggle the GPIOs once
* before falling back to a normal memcpy. Reading the higher layer code shows
* that this is indeed the case, but add a BUG_ON() to future proof.
*/
static void gf_copy_from(struct map_info *map, void *to, unsigned long from, ssize_t len)
{
struct async_state *state = gf_map_info_to_state(map);
gf_set_gpios(state, from);
/* BUG if operation crosses the win_size */
BUG_ON(!((from + len) % state->win_size <= (from + len)));
/* operation does not cross the win_size, so one shot it */
memcpy_fromio(to, map->virt + (from % state->win_size), len);
}
/**
* gf_write() - write a word at the specified offset
* @map: MTD map state
* @ofs: desired offset to write
*/
static void gf_write(struct map_info *map, map_word d1, unsigned long ofs)
{
struct async_state *state = gf_map_info_to_state(map);
uint16_t d;
gf_set_gpios(state, ofs);
d = d1.x[0];
writew(d, map->virt + (ofs % state->win_size));
}
/**
* gf_copy_to() - copy a chunk of data to the flash
* @map: MTD map state
* @to: flash offset to copy to
* @from: memory to copy from
* @len: how much to copy
*
* See gf_copy_from() caveat.
*/
static void gf_copy_to(struct map_info *map, unsigned long to,
const void *from, ssize_t len)
{
struct async_state *state = gf_map_info_to_state(map);
gf_set_gpios(state, to);
/* BUG if operation crosses the win_size */
BUG_ON(!((to + len) % state->win_size <= (to + len)));
/* operation does not cross the win_size, so one shot it */
memcpy_toio(map->virt + (to % state->win_size), from, len);
}
static const char * const part_probe_types[] = {
"cmdlinepart", "RedBoot", NULL };
/**
* gpio_flash_probe() - setup a mapping for a GPIO assisted flash
* @pdev: platform device
*
* The platform resource layout expected looks something like:
* struct mtd_partition partitions[] = { ... };
* struct physmap_flash_data flash_data = { ... };
* unsigned flash_gpios[] = { GPIO_XX, GPIO_XX, ... };
* struct resource flash_resource[] = {
* {
* .name = "cfi_probe",
* .start = 0x20000000,
* .end = 0x201fffff,
* .flags = IORESOURCE_MEM,
* }, {
* .start = (unsigned long)flash_gpios,
* .end = ARRAY_SIZE(flash_gpios),
* .flags = IORESOURCE_IRQ,
* }
* };
* struct platform_device flash_device = {
* .name = "gpio-addr-flash",
* .dev = { .platform_data = &flash_data, },
* .num_resources = ARRAY_SIZE(flash_resource),
* .resource = flash_resource,
* ...
* };
*/
static int gpio_flash_probe(struct platform_device *pdev)
{
size_t i, arr_size;
struct physmap_flash_data *pdata;
struct resource *memory;
struct resource *gpios;
struct async_state *state;
pdata = dev_get_platdata(&pdev->dev);
memory = platform_get_resource(pdev, IORESOURCE_MEM, 0);
gpios = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
if (!memory || !gpios || !gpios->end)
return -EINVAL;
arr_size = sizeof(int) * gpios->end;
state = kzalloc(sizeof(*state) + arr_size, GFP_KERNEL);
if (!state)
return -ENOMEM;
/*
* We cast start/end to known types in the boards file, so cast
* away their pointer types here to the known types (gpios->xxx).
*/
state->gpio_count = gpios->end;
state->gpio_addrs = (void *)(unsigned long)gpios->start;
state->gpio_values = (void *)(state + 1);
state->win_size = resource_size(memory);
memset(state->gpio_values, 0xff, arr_size);
state->map.name = DRIVER_NAME;
state->map.read = gf_read;
state->map.copy_from = gf_copy_from;
state->map.write = gf_write;
state->map.copy_to = gf_copy_to;
state->map.bankwidth = pdata->width;
state->map.size = state->win_size * (1 << state->gpio_count);
state->map.virt = ioremap_nocache(memory->start, state->map.size);
state->map.phys = NO_XIP;
state->map.map_priv_1 = (unsigned long)state;
platform_set_drvdata(pdev, state);
i = 0;
do {
if (gpio_request(state->gpio_addrs[i], DRIVER_NAME)) {
pr_devinit(KERN_ERR PFX "failed to request gpio %d\n",
state->gpio_addrs[i]);
while (i--)
gpio_free(state->gpio_addrs[i]);
kfree(state);
return -EBUSY;
}
gpio_direction_output(state->gpio_addrs[i], 0);
} while (++i < state->gpio_count);
pr_devinit(KERN_NOTICE PFX "probing %d-bit flash bus\n",
state->map.bankwidth * 8);
state->mtd = do_map_probe(memory->name, &state->map);
if (!state->mtd) {
for (i = 0; i < state->gpio_count; ++i)
gpio_free(state->gpio_addrs[i]);
kfree(state);
return -ENXIO;
}
mtd_device_parse_register(state->mtd, part_probe_types, NULL,
pdata->parts, pdata->nr_parts);
return 0;
}
static int gpio_flash_remove(struct platform_device *pdev)
{
struct async_state *state = platform_get_drvdata(pdev);
size_t i = 0;
do {
gpio_free(state->gpio_addrs[i]);
} while (++i < state->gpio_count);
mtd_device_unregister(state->mtd);
map_destroy(state->mtd);
kfree(state);
return 0;
}
static struct platform_driver gpio_flash_driver = {
.probe = gpio_flash_probe,
.remove = gpio_flash_remove,
.driver = {
.name = DRIVER_NAME,
},
};
module_platform_driver(gpio_flash_driver);
MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
MODULE_DESCRIPTION("MTD map driver for flashes addressed physically and with gpios");
MODULE_LICENSE("GPL");