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authorMike Turquette <mturquette@ti.com>2010-02-24 12:06:00 -0700
committerPaul Walmsley <paul@pwsan.com>2010-02-24 12:06:00 -0700
commita7e069fc5a560c096a2597d7be27f45fb4a01df7 (patch)
tree5171d2350215339101f9966ea17decbb1819d7f3 /arch/arm/mach-omap2/clock34xx.c
parentc23a97d377077c67e01f7526de3a411b316ee4f6 (diff)
OMAP3630: Clock: Workaround for DPLL HS divider limitation
This patch implements a workaround for the DPLL HS divider limitation in OMAP3630 as given by Errata ID: i556. Errata: When PWRDN bit is set, it resets the internal HSDIVIDER divide-by value (Mx). The reset value gets loaded instead of the previous value. The following HSDIVIDERs exhibit above behavior: . DPLL4 : M6 / M5 / M4 / M3 / M2 (CM_CLKEN_PLL[31:26] register bits) . DPLL3 : M3 (CM_CLKEN_PLL[12] register bit). Work Around: It is mandatory to apply the following sequence to ensure the write value will be loaded in DPLL HSDIVIDER FSM: The global sequence when using PWRDN bit is the following: . Disable Mx HSDIVIDER clock output related functional clock enable bits (in CM_FCLKEN_xxx / CM_ICLKEN_xxx) . Enable PWRDN bit of HSDIVIDER . Disable PWRDN bit of HSDIVIDER . Read current HSDIVIDER register value . Write different value in HSDIVIDER register . Write expected value in HSDIVIDER register . Enable Mx HSDIVIDER clock output related functional clocks (CM_FCLKEN_xxx / CM_ICLKEN_xxx) Signed-off-by: Mike Turquette <mturquette@ti.com> Signed-off-by: Vishwanath BS <vishwanath.bs@ti.com> Signed-off-by: Vijaykumar GN <vijaykumar.gn@ti.com> [paul@pwsan.com: updated patch to apply; made workaround function static; marked as being 36xx-specific] Signed-off-by: Paul Walmsley <paul@pwsan.com>
Diffstat (limited to 'arch/arm/mach-omap2/clock34xx.c')
-rw-r--r--arch/arm/mach-omap2/clock34xx.c43
1 files changed, 43 insertions, 0 deletions
diff --git a/arch/arm/mach-omap2/clock34xx.c b/arch/arm/mach-omap2/clock34xx.c
index de7391b6bcfd..9039e8cbe487 100644
--- a/arch/arm/mach-omap2/clock34xx.c
+++ b/arch/arm/mach-omap2/clock34xx.c
@@ -150,6 +150,49 @@ const struct clkops clkops_omap3430es2_hsotgusb_wait = {
.find_companion = omap2_clk_dflt_find_companion,
};
+/**
+ * omap36xx_pwrdn_clk_enable_with_hsdiv_restore - enable clocks suffering
+ * from HSDivider PWRDN problem Implements Errata ID: i556.
+ * @clk: DPLL output struct clk
+ *
+ * 3630 only: dpll3_m3_ck, dpll4_m2_ck, dpll4_m3_ck, dpll4_m4_ck,
+ * dpll4_m5_ck & dpll4_m6_ck dividers gets loaded with reset
+ * valueafter their respective PWRDN bits are set. Any dummy write
+ * (Any other value different from the Read value) to the
+ * corresponding CM_CLKSEL register will refresh the dividers.
+ */
+static int omap36xx_pwrdn_clk_enable_with_hsdiv_restore(struct clk *clk)
+{
+ u32 dummy_v, orig_v, clksel_shift;
+ int ret;
+
+ /* Clear PWRDN bit of HSDIVIDER */
+ ret = omap2_dflt_clk_enable(clk);
+
+ /* Restore the dividers */
+ if (!ret) {
+ clksel_shift = __ffs(clk->parent->clksel_mask);
+ orig_v = __raw_readl(clk->parent->clksel_reg);
+ dummy_v = orig_v;
+
+ /* Write any other value different from the Read value */
+ dummy_v ^= (1 << clksel_shift);
+ __raw_writel(dummy_v, clk->parent->clksel_reg);
+
+ /* Write the original divider */
+ __raw_writel(orig_v, clk->parent->clksel_reg);
+ }
+
+ return ret;
+}
+
+const struct clkops clkops_omap36xx_pwrdn_with_hsdiv_wait_restore = {
+ .enable = omap36xx_pwrdn_clk_enable_with_hsdiv_restore,
+ .disable = omap2_dflt_clk_disable,
+ .find_companion = omap2_clk_dflt_find_companion,
+ .find_idlest = omap2_clk_dflt_find_idlest,
+};
+
const struct clkops omap3_clkops_noncore_dpll_ops = {
.enable = omap3_noncore_dpll_enable,
.disable = omap3_noncore_dpll_disable,