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davinci: clock: add support for setting sysclk rate

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Setting sysclk rate will be useful in cases where the
sysclk is not at a fixed ratio to the PLL output but
can asynchronously be changed.

This support forms the basis of attempt to keep the AEMIF
clock constant on OMAP-L138 even as PLL0 output changes
as ARM clock is changed to save power.

This patch has been tested on OMAP-L138.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
This commit is contained in:
Sekhar Nori 2010-07-20 16:46:49 +05:30 committed by Kevin Hilman
parent 0a477f6b8c
commit b39639b820
2 changed files with 78 additions and 0 deletions
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73
arch/arm/mach-davinci/clock.c
View file

@ -287,6 +287,79 @@ static unsigned long clk_sysclk_recalc(struct clk *clk)
return rate;
}
int davinci_set_sysclk_rate(struct clk *clk, unsigned long rate)
{
unsigned v;
struct pll_data *pll;
unsigned long input;
unsigned ratio = 0;
/* If this is the PLL base clock, wrong function to call */
if (clk->pll_data)
return -EINVAL;
/* There must be a parent... */
if (WARN_ON(!clk->parent))
return -EINVAL;
/* ... the parent must be a PLL... */
if (WARN_ON(!clk->parent->pll_data))
return -EINVAL;
/* ... and this clock must have a divider. */
if (WARN_ON(!clk->div_reg))
return -EINVAL;
pll = clk->parent->pll_data;
input = clk->parent->rate;
/* If pre-PLL, source clock is before the multiplier and divider(s) */
if (clk->flags & PRE_PLL)
input = pll->input_rate;
if (input > rate) {
/*
* Can afford to provide an output little higher than requested
* only if maximum rate supported by hardware on this sysclk
* is known.
*/
if (clk->maxrate) {
ratio = DIV_ROUND_CLOSEST(input, rate);
if (input / ratio > clk->maxrate)
ratio = 0;
}
if (ratio == 0)
ratio = DIV_ROUND_UP(input, rate);
ratio--;
}
if (ratio > PLLDIV_RATIO_MASK)
return -EINVAL;
do {
v = __raw_readl(pll->base + PLLSTAT);
} while (v & PLLSTAT_GOSTAT);
v = __raw_readl(pll->base + clk->div_reg);
v &= ~PLLDIV_RATIO_MASK;
v |= ratio | PLLDIV_EN;
__raw_writel(v, pll->base + clk->div_reg);
v = __raw_readl(pll->base + PLLCMD);
v |= PLLCMD_GOSET;
__raw_writel(v, pll->base + PLLCMD);
do {
v = __raw_readl(pll->base + PLLSTAT);
} while (v & PLLSTAT_GOSTAT);
return 0;
}
EXPORT_SYMBOL(davinci_set_sysclk_rate);
static unsigned long clk_leafclk_recalc(struct clk *clk)
{
if (WARN_ON(!clk->parent))

5
arch/arm/mach-davinci/clock.h
View file

@ -70,6 +70,9 @@
#include <linux/list.h>
#include <asm/clkdev.h>
#define PLLSTAT_GOSTAT BIT(0)
#define PLLCMD_GOSET BIT(0)
struct pll_data {
u32 phys_base;
void __iomem *base;
@ -86,6 +89,7 @@ struct clk {
struct module *owner;
const char *name;
unsigned long rate;
unsigned long maxrate; /* H/W supported max rate */
u8 usecount;
u8 lpsc;
u8 gpsc;
@ -118,6 +122,7 @@ struct clk {
int davinci_clk_init(struct clk_lookup *clocks);
int davinci_set_pllrate(struct pll_data *pll, unsigned int prediv,
unsigned int mult, unsigned int postdiv);
int davinci_set_sysclk_rate(struct clk *clk, unsigned long rate);
extern struct platform_device davinci_wdt_device;
extern void davinci_watchdog_reset(struct platform_device *);