OMAP3 clock: initialize SDRC timings at kernel start

On the OMAP3, initialize SDRC timings when the kernel boots.  This ensures
that the kernel is running with known, optimized SDRC timings, rather than
whatever was configured by the bootloader.

Signed-off-by: Paul Walmsley <paul@pwsan.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/arch/arm/mach-omap2/io.c b/arch/arm/mach-omap2/io.c
index 32afd9448216..3a86b0f66031 100644
--- a/arch/arm/mach-omap2/io.c
+++ b/arch/arm/mach-omap2/io.c
@@ -21,6 +21,7 @@
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/io.h>
+#include <linux/clk.h>
 
 #include <asm/tlb.h>
 
@@ -241,6 +242,40 @@ void __init omap2_map_common_io(void)
 	omapfb_reserve_sdram();
 }
 
+/*
+ * omap2_init_reprogram_sdrc - reprogram SDRC timing parameters
+ *
+ * Sets the CORE DPLL3 M2 divider to the same value that it's at
+ * currently.  This has the effect of setting the SDRC SDRAM AC timing
+ * registers to the values currently defined by the kernel.  Currently
+ * only defined for OMAP3; will return 0 if called on OMAP2.  Returns
+ * -EINVAL if the dpll3_m2_ck cannot be found, 0 if called on OMAP2,
+ * or passes along the return value of clk_set_rate().
+ */
+static int __init _omap2_init_reprogram_sdrc(void)
+{
+	struct clk *dpll3_m2_ck;
+	int v = -EINVAL;
+	long rate;
+
+	if (!cpu_is_omap34xx())
+		return 0;
+
+	dpll3_m2_ck = clk_get(NULL, "dpll3_m2_ck");
+	if (!dpll3_m2_ck)
+		return -EINVAL;
+
+	rate = clk_get_rate(dpll3_m2_ck);
+	pr_info("Reprogramming SDRC clock to %ld Hz\n", rate);
+	v = clk_set_rate(dpll3_m2_ck, rate);
+	if (v)
+		pr_err("dpll3_m2_clk rate change failed: %d\n", v);
+
+	clk_put(dpll3_m2_ck);
+
+	return v;
+}
+
 void __init omap2_init_common_hw(struct omap_sdrc_params *sp)
 {
 	omap2_mux_init();
@@ -249,6 +284,7 @@ void __init omap2_init_common_hw(struct omap_sdrc_params *sp)
 	clkdm_init(clockdomains_omap, clkdm_pwrdm_autodeps);
 	omap2_clk_init();
 	omap2_sdrc_init(sp);
+	_omap2_init_reprogram_sdrc();
 #endif
 	gpmc_init();
 }