diff options
author | Sekhar Nori <nsekhar@ti.com> | 2009-08-31 15:48:03 +0530 |
---|---|---|
committer | Kevin Hilman <khilman@deeprootsystems.com> | 2009-11-25 10:21:20 -0800 |
commit | d6a61563f9e934ef20a1338780082f63802c8908 (patch) | |
tree | 543d650b9c87c6a63974db565d803ad26bf1ee38 /arch/arm | |
parent | de381a91f544008f4f99571e2ef1f60b92d5f0cf (diff) |
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>
Diffstat (limited to 'arch/arm')
-rw-r--r-- | arch/arm/mach-davinci/clock.c | 114 | ||||
-rw-r--r-- | arch/arm/mach-davinci/clock.h | 8 |
2 files changed, 119 insertions, 3 deletions
diff --git a/arch/arm/mach-davinci/clock.c b/arch/arm/mach-davinci/clock.c index 6de1e3428f1..09e0e1c00a5 100644 --- a/arch/arm/mach-davinci/clock.c +++ b/arch/arm/mach-davinci/clock.c @@ -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) { + unsigned long flags; + int ret = -EINVAL; + if (clk == NULL || IS_ERR(clk)) - return -EINVAL; + return ret; - /* changing the clk rate is not supported */ - return -EINVAL; + 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; diff --git a/arch/arm/mach-davinci/clock.h b/arch/arm/mach-davinci/clock.h index 202b9ff27b9..a75d3f70b35 100644 --- a/arch/arm/mach-davinci/clock.h +++ b/arch/arm/mach-davinci/clock.h @@ -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; |