davinci: support changing the clock rate in clock framework

clk_round_rate, clk_set_rate have been updated to handle dynamic
frequency changes.

The motivation behind the changes is to support dynamic CPU frequency
change.

davinci_set_pllrate() changes the PLL rate of a given PLL. This function
has been presented as a generic function though it has been tested only
on OMAP-L138 EVM. No other currently available DaVinci device will probably
use this function, but any future device specific changes will hopefully be
small enough to get taken care using a cpu_is_xxx() macro.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
This commit is contained in:
Sekhar Nori 2009-08-31 15:48:03 +05:30 committed by Kevin Hilman
parent de381a91f5
commit d6a61563f9
2 changed files with 120 additions and 4 deletions

View file

@ -19,6 +19,7 @@
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/delay.h>
#include <mach/hardware.h>
@ -99,17 +100,44 @@ long clk_round_rate(struct clk *clk, unsigned long rate)
if (clk == NULL || IS_ERR(clk))
return -EINVAL;
if (clk->round_rate)
return clk->round_rate(clk, rate);
return clk->rate;
}
EXPORT_SYMBOL(clk_round_rate);
/* Propagate rate to children */
static void propagate_rate(struct clk *root)
{
struct clk *clk;
list_for_each_entry(clk, &root->children, childnode) {
if (clk->recalc)
clk->rate = clk->recalc(clk);
propagate_rate(clk);
}
}
int clk_set_rate(struct clk *clk, unsigned long rate)
{
if (clk == NULL || IS_ERR(clk))
return -EINVAL;
unsigned long flags;
int ret = -EINVAL;
/* changing the clk rate is not supported */
return -EINVAL;
if (clk == NULL || IS_ERR(clk))
return ret;
spin_lock_irqsave(&clockfw_lock, flags);
if (clk->set_rate)
ret = clk->set_rate(clk, rate);
if (ret == 0) {
if (clk->recalc)
clk->rate = clk->recalc(clk);
propagate_rate(clk);
}
spin_unlock_irqrestore(&clockfw_lock, flags);
return ret;
}
EXPORT_SYMBOL(clk_set_rate);
@ -296,6 +324,86 @@ static unsigned long clk_pllclk_recalc(struct clk *clk)
return rate;
}
/**
* davinci_set_pllrate - set the output rate of a given PLL.
*
* Note: Currently tested to work with OMAP-L138 only.
*
* @pll: pll whose rate needs to be changed.
* @prediv: The pre divider value. Passing 0 disables the pre-divider.
* @pllm: The multiplier value. Passing 0 leads to multiply-by-one.
* @postdiv: The post divider value. Passing 0 disables the post-divider.
*/
int davinci_set_pllrate(struct pll_data *pll, unsigned int prediv,
unsigned int mult, unsigned int postdiv)
{
u32 ctrl;
unsigned int locktime;
if (pll->base == NULL)
return -EINVAL;
/*
* PLL lock time required per OMAP-L138 datasheet is
* (2000 * prediv)/sqrt(pllm) OSCIN cycles. We approximate sqrt(pllm)
* as 4 and OSCIN cycle as 25 MHz.
*/
if (prediv) {
locktime = ((2000 * prediv) / 100);
prediv = (prediv - 1) | PLLDIV_EN;
} else {
locktime = 20;
}
if (postdiv)
postdiv = (postdiv - 1) | PLLDIV_EN;
if (mult)
mult = mult - 1;
ctrl = __raw_readl(pll->base + PLLCTL);
/* Switch the PLL to bypass mode */
ctrl &= ~(PLLCTL_PLLENSRC | PLLCTL_PLLEN);
__raw_writel(ctrl, pll->base + PLLCTL);
/*
* Wait for 4 OSCIN/CLKIN cycles to ensure that the PLLC has switched
* to bypass mode. Delay of 1us ensures we are good for all > 4MHz
* OSCIN/CLKIN inputs. Typically the input is ~25MHz.
*/
udelay(1);
/* Reset and enable PLL */
ctrl &= ~(PLLCTL_PLLRST | PLLCTL_PLLDIS);
__raw_writel(ctrl, pll->base + PLLCTL);
if (pll->flags & PLL_HAS_PREDIV)
__raw_writel(prediv, pll->base + PREDIV);
__raw_writel(mult, pll->base + PLLM);
if (pll->flags & PLL_HAS_POSTDIV)
__raw_writel(postdiv, pll->base + POSTDIV);
/*
* Wait for PLL to reset properly, OMAP-L138 datasheet says
* 'min' time = 125ns
*/
udelay(1);
/* Bring PLL out of reset */
ctrl |= PLLCTL_PLLRST;
__raw_writel(ctrl, pll->base + PLLCTL);
udelay(locktime);
/* Remove PLL from bypass mode */
ctrl |= PLLCTL_PLLEN;
__raw_writel(ctrl, pll->base + PLLCTL);
return 0;
}
EXPORT_SYMBOL(davinci_set_pllrate);
int __init davinci_clk_init(struct davinci_clk *clocks)
{
struct davinci_clk *c;

View file

@ -22,6 +22,10 @@
/* PLL/Reset register offsets */
#define PLLCTL 0x100
#define PLLCTL_PLLEN BIT(0)
#define PLLCTL_PLLPWRDN BIT(1)
#define PLLCTL_PLLRST BIT(3)
#define PLLCTL_PLLDIS BIT(4)
#define PLLCTL_PLLENSRC BIT(5)
#define PLLCTL_CLKMODE BIT(8)
#define PLLM 0x110
@ -74,6 +78,8 @@ struct clk {
struct pll_data *pll_data;
u32 div_reg;
unsigned long (*recalc) (struct clk *);
int (*set_rate) (struct clk *clk, unsigned long rate);
int (*round_rate) (struct clk *clk, unsigned long rate);
};
/* Clock flags */
@ -97,6 +103,8 @@ struct davinci_clk {
}
int davinci_clk_init(struct davinci_clk *clocks);
int davinci_set_pllrate(struct pll_data *pll, unsigned int prediv,
unsigned int mult, unsigned int postdiv);
extern struct platform_device davinci_wdt_device;