- 根目录:
- arch
- arm
- mach-omap2
- clkt_clksel.c
/*
* clkt_clksel.c - OMAP2/3/4 clksel clock functions
*
* Copyright (C) 2005-2008 Texas Instruments, Inc.
* Copyright (C) 2004-2010 Nokia Corporation
*
* Contacts:
* Richard Woodruff <r-woodruff2@ti.com>
* Paul Walmsley
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*
* clksel clocks are clocks that do not have a fixed parent, or that
* can divide their parent's rate, or possibly both at the same time, based
* on the contents of a hardware register bitfield.
*
* All of the various mux and divider settings can be encoded into
* struct clksel* data structures, and then these can be autogenerated
* from some hardware database for each new chip generation. This
* should avoid the need to write, review, and validate a lot of new
* clock code for each new chip, since it can be exported from the SoC
* design flow. This is now done on OMAP4.
*
* The fusion of mux and divider clocks is a software creation. In
* hardware reality, the multiplexer (parent selection) and the
* divider exist separately. XXX At some point these clksel clocks
* should be split into "divider" clocks and "mux" clocks to better
* match the hardware.
*
* (The name "clksel" comes from the name of the corresponding
* register field in the OMAP2/3 family of SoCs.)
*
* XXX Currently these clocks are only used in the OMAP2/3/4 code, but
* many of the OMAP1 clocks should be convertible to use this
* mechanism.
*/
#undef DEBUG
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <plat/clock.h>
#include "clock.h"
/* Private functions */
/**
* _get_clksel_by_parent() - return clksel struct for a given clk & parent
* @clk: OMAP struct clk ptr to inspect
* @src_clk: OMAP struct clk ptr of the parent clk to search for
*
* Scan the struct clksel array associated with the clock to find
* the element associated with the supplied parent clock address.
* Returns a pointer to the struct clksel on success or NULL on error.
*/
static const struct clksel *_get_clksel_by_parent(struct clk *clk,
struct clk *src_clk)
{
const struct clksel *clks;
for (clks = clk->clksel; clks->parent; clks++)
if (clks->parent == src_clk)
break; /* Found the requested parent */
if (!clks->parent) {
/* This indicates a data problem */
WARN(1, "clock: Could not find parent clock %s in clksel array "
"of clock %s\n", src_clk->name, clk->name);
return NULL;
}
return clks;
}
/**
* _get_div_and_fieldval() - find the new clksel divisor and field value to use
* @src_clk: planned new parent struct clk *
* @clk: struct clk * that is being reparented
* @field_val: pointer to a u32 to contain the register data for the divisor
*
* Given an intended new parent struct clk * @src_clk, and the struct
* clk * @clk to the clock that is being reparented, find the
* appropriate rate divisor for the new clock (returned as the return
* value), and the corresponding register bitfield data to program to
* reach that divisor (returned in the u32 pointed to by @field_val).
* Returns 0 on error, or returns the newly-selected divisor upon
* success (in this latter case, the corresponding register bitfield
* value is passed back in the variable pointed to by @field_val)
*/
static u8 _get_div_and_fieldval(struct clk *src_clk, struct clk *clk,
u32 *field_val)
{
const struct clksel *clks;
const struct clksel_rate *clkr, *max_clkr = NULL;
u8 max_div = 0;
clks = _get_clksel_by_parent(clk, src_clk);
if (!clks)
return 0;
/*
* Find the highest divisor (e.g., the one resulting in the
* lowest rate) to use as the default. This should avoid
* clock rates that are too high for the device. XXX A better
* solution here would be to try to determine if there is a
* divisor matching the original clock rate before the parent
* switch, and if it cannot be found, to fall back to the
* highest divisor.
*/
for (clkr = clks->rates; clkr->div; clkr++) {
if (!(clkr->flags & cpu_mask))
continue;
if (clkr->div > max_div) {
max_div = clkr->div;
max_clkr = clkr;
}
}
if (max_div == 0) {
/* This indicates an error in the clksel data */
WARN(1, "clock: Could not find divisor for clock %s parent %s"
"\n", clk->name, src_clk->parent->name);
return 0;
}
*field_val = max_clkr->val;
return max_div;
}
/**
* _write_clksel_reg() - program a clock's clksel register in hardware
* @clk: struct clk * to program
* @v: clksel bitfield value to program (with LSB at bit 0)
*
* Shift the clksel register bitfield value @v to its appropriate
* location in the clksel register and write it in. This function
* will ensure that the write to the clksel_reg reaches its
* destination before returning -- important since PRM and CM register
* accesses can be quite slow compared to ARM cycles -- but does not
* take into account any time the hardware might take to switch the
* clock source.
*/
static void _write_clksel_reg(struct clk *clk, u32 field_val)
{
u32 v;
v = __raw_readl(clk->clksel_reg);
v &= ~clk->clksel_mask;
v |= field_val << __ffs(clk->clksel_mask);
__raw_writel(v, clk->clksel_reg);
v = __raw_readl(clk->clksel_reg); /* OCP barrier */
}
/**
* _clksel_to_divisor() - turn clksel field value into integer divider
* @clk: OMAP struct clk to use
* @field_val: register field value to find
*
* Given a struct clk of a rate-selectable clksel clock, and a register field
* value to search for, find the corresponding clock divisor. The register
* field value should be pre-masked and shifted down so the LSB is at bit 0
* before calling. Returns 0 on error or returns the actual integer divisor
* upon success.
*/
static u32 _clksel_to_divisor(struct clk *clk, u32 field_val)
{
const struct clksel *clks;
const struct clksel_rate *clkr;
clks = _get_clksel_by_parent(clk, clk->parent);
if (!clks)
return 0;
for (clkr = clks->rates; clkr->div; clkr++) {
if (!(clkr->flags & cpu_mask))
continue;
if (clkr->val == field_val)
break;
}
if (!clkr->div) {
/* This indicates a data error */
WARN(1, "clock: Could not find fieldval %d for clock %s parent "
"%s\n", field_val, clk->name, clk->parent->name);
return 0;
}
return clkr->div;
}
/**
* _divisor_to_clksel() - turn clksel integer divisor into a field value
* @clk: OMAP struct clk to use
* @div: integer divisor to search for
*
* Given a struct clk of a rate-selectable clksel clock, and a clock
* divisor, find the corresponding register field value. Returns the
* register field value _before_ left-shifting (i.e., LSB is at bit
* 0); or returns 0xFFFFFFFF (~0) upon error.
*/
static u32 _divisor_to_clksel(struct clk *clk, u32 div)
{
const struct clksel *clks;
const struct clksel_rate *clkr;
/* should never happen */
WARN_ON(div == 0);
clks = _get_clksel_by_parent(clk, clk->parent);
if (!clks)
return ~0;
for (clkr = clks->rates; clkr->div; clkr++) {
if (!(clkr->flags & cpu_mask))
continue;
if (clkr->div == div)
break;
}
if (!clkr->div) {
pr_err("clock: Could not find divisor %d for clock %s parent "
"%s\n", div, clk->name, clk->parent->name);
return ~0;
}
return clkr->val;
}
/**
* _read_divisor() - get current divisor applied to parent clock (from hdwr)
* @clk: OMAP struct clk to use.
*
* Read the current divisor register value for @clk that is programmed
* into the hardware, convert it into the actual divisor value, and
* return it; or return 0 on error.
*/
static u32 _read_divisor(struct clk *clk)
{
u32 v;
if (!clk->clksel || !clk->clksel_mask)
return 0;
v = __raw_readl(clk->clksel_reg);
v &= clk->clksel_mask;
v >>= __ffs(clk->clksel_mask);
return _clksel_to_divisor(clk, v);
}
/* Public functions */
/**
* omap2_clksel_round_rate_div() - find divisor for the given clock and rate
* @clk: OMAP struct clk to use
* @target_rate: desired clock rate
* @new_div: ptr to where we should store the divisor
*
* Finds 'best' divider value in an array based on the source and target
* rates. The divider array must be sorted with smallest divider first.
* This function is also used by the DPLL3 M2 divider code.
*
* Returns the rounded clock rate or returns 0xffffffff on error.
*/
u32 omap2_clksel_round_rate_div(struct clk *clk, unsigned long target_rate,
u32 *new_div)
{
unsigned long test_rate;
const struct clksel *clks;
const struct clksel_rate *clkr;
u32 last_div = 0;
if (!clk->clksel || !clk->clksel_mask)
return ~0;
pr_debug("clock: clksel_round_rate_div: %s target_rate %ld\n",
clk->name, target_rate);
*new_div = 1;
clks = _get_clksel_by_parent(clk, clk->parent);
if (!clks)
return ~0;
for (clkr = clks->rates; clkr->div; clkr++) {
if (!(clkr->flags & cpu_mask))
continue;
/* Sanity check */
if (clkr->div <= last_div)
pr_err("clock: clksel_rate table not sorted "
"for clock %s", clk->name);
last_div = clkr->div;
test_rate = clk->parent->rate / clkr->div;
if (test_rate <= target_rate)
break; /* found it */
}
if (!clkr->div) {
pr_err("clock: Could not find divisor for target "
"rate %ld for clock %s parent %s\n", target_rate,
clk->name, clk->parent->name);
return ~0;
}
*new_div = clkr->div;
pr_debug("clock: new_div = %d, new_rate = %ld\n", *new_div,
(clk->parent->rate / clkr->div));
return clk->parent->rate / clkr->div;
}
/*
* Clocktype interface functions to the OMAP clock code
* (i.e., those used in struct clk field function pointers, etc.)
*/
/**
* omap2_init_clksel_parent() - set a clksel clk's parent field from the hdwr
* @clk: OMAP clock struct ptr to use
*
* Given a pointer @clk to a source-selectable struct clk, read the
* hardware register and determine what its parent is currently set
* to. Update @clk's .parent field with the appropriate clk ptr. No
* return value.
*/
void omap2_init_clksel_parent(struct clk *clk)
{
const struct clksel *clks;
const struct clksel_rate *clkr;
u32 r, found = 0;
if (!clk->clksel || !clk->clksel_mask)
return;
r = __raw_readl(clk->clksel_reg) & clk->clksel_mask;
r >>= __ffs(clk->clksel_mask);
for (clks = clk->clksel; clks->parent && !found; clks++) {
for (clkr = clks->rates; clkr->div && !found; clkr++) {
if (!(clkr->flags & cpu_mask))
continue;
if (clkr->val == r) {
if (clk->parent != clks->parent) {
pr_debug("clock: inited %s parent "
"to %s (was %s)\n",
clk->name, clks->parent->name,
((clk->parent) ?
clk->parent->name : "NULL"));
clk_reparent(clk, clks->parent);
};
found = 1;
}
}
}
/* This indicates a data error */
WARN(!found, "clock: %s: init parent: could not find regval %0x\n",
clk->name, r);
return;
}
/**
* omap2_clksel_recalc() - function ptr to pass via struct clk .recalc field
* @clk: struct clk *
*
* This function is intended to be called only by the clock framework.
* Each clksel clock should have its struct clk .recalc field set to this
* function. Returns the clock's current rate, based on its parent's rate
* and its current divisor setting in the hardware.
*/
unsigned long omap2_clksel_recalc(struct clk *clk)
{
unsigned long rate;
u32 div = 0;
div = _read_divisor(clk);
if (div == 0)
return clk->rate;
rate = clk->parent->rate / div;
pr_debug("clock: %s: recalc'd rate is %ld (div %d)\n", clk->name,
rate, div);
return rate;
}
/**
* omap2_clksel_round_rate() - find rounded rate for the given clock and rate
* @clk: OMAP struct clk to use
* @target_rate: desired clock rate
*
* This function is intended to be called only by the clock framework.
* Finds best target rate based on the source clock and possible dividers.
* rates. The divider array must be sorted with smallest divider first.
*
* Returns the rounded clock rate or returns 0xffffffff on error.
*/
long omap2_clksel_round_rate(struct clk *clk, unsigned long target_rate)
{
u32 new_div;
return omap2_clksel_round_rate_div(clk, target_rate, &new_div);
}
/**
* omap2_clksel_set_rate() - program clock rate in hardware
* @clk: struct clk * to program rate
* @rate: target rate to program
*
* This function is intended to be called only by the clock framework.
* Program @clk's rate to @rate in the hardware. The clock can be
* either enabled or disabled when this happens, although if the clock
* is enabled, some downstream devices may glitch or behave
* unpredictably when the clock rate is changed - this depends on the
* hardware. This function does not currently check the usecount of
* the clock, so if multiple drivers are using the clock, and the rate
* is changed, they will all be affected without any notification.
* Returns -EINVAL upon error, or 0 upon success.
*/
int omap2_clksel_set_rate(struct clk *clk, unsigned long rate)
{
u32 field_val, validrate, new_div = 0;
if (!clk->clksel || !clk->clksel_mask)
return -EINVAL;
validrate = omap2_clksel_round_rate_div(clk, rate, &new_div);
if (validrate != rate)
return -EINVAL;
field_val = _divisor_to_clksel(clk, new_div);
if (field_val == ~0)
return -EINVAL;
_write_clksel_reg(clk, field_val);
clk->rate = clk->parent->rate / new_div;
pr_debug("clock: %s: set rate to %ld\n", clk->name, clk->rate);
return 0;
}
/*
* Clksel parent setting function - not passed in struct clk function
* pointer - instead, the OMAP clock code currently assumes that any
* parent-setting clock is a clksel clock, and calls
* omap2_clksel_set_parent() by default
*/
/**
* omap2_clksel_set_parent() - change a clock's parent clock
* @clk: struct clk * of the child clock
* @new_parent: struct clk * of the new parent clock
*
* This function is intended to be called only by the clock framework.
* Change the parent clock of clock @clk to @new_parent. This is
* intended to be used while @clk is disabled. This function does not
* currently check the usecount of the clock, so if multiple drivers
* are using the clock, and the parent is changed, they will all be
* affected without any notification. Returns -EINVAL upon error, or
* 0 upon success.
*/
int omap2_clksel_set_parent(struct clk *clk, struct clk *new_parent)
{
u32 field_val = 0;
u32 parent_div;
if (!clk->clksel || !clk->clksel_mask)
return -EINVAL;
parent_div = _get_div_and_fieldval(new_parent, clk, &field_val);
if (!parent_div)
return -EINVAL;
_write_clksel_reg(clk, field_val);
clk_reparent(clk, new_parent);
/* CLKSEL clocks follow their parents' rates, divided by a divisor */
clk->rate = new_parent->rate;
if (parent_div > 0)
clk->rate /= parent_div;
pr_debug("clock: %s: set parent to %s (new rate %ld)\n",
clk->name, clk->parent->name, clk->rate);
return 0;
}