summaryrefslogtreecommitdiffstats
path: root/arch/arm/mach-davinci/clock.c
diff options
context:
space:
mode:
authorSekhar Nori <nsekhar@ti.com>2009-08-31 15:48:03 +0530
committerKevin Hilman <khilman@deeprootsystems.com>2009-11-25 10:21:20 -0800
commitd6a61563f9e934ef20a1338780082f63802c8908 (patch)
tree543d650b9c87c6a63974db565d803ad26bf1ee38 /arch/arm/mach-davinci/clock.c
parentde381a91f544008f4f99571e2ef1f60b92d5f0cf (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/mach-davinci/clock.c')
-rw-r--r--arch/arm/mach-davinci/clock.c114
1 files changed, 111 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;