OMAP3 clock: add a short delay when lowering CORE clk rate

When changing the SDRAM clock from 166MHz to 83MHz via the CORE DPLL M2
divider, add a short delay before returning to SDRAM to allow the SDRC
time to stabilize.  Without this delay, the system is prone to random
panics upon re-entering SDRAM.

This time delay varies based on MPU frequency.  At 500MHz MPU frequency at
room temperature, 64 loops seems to work okay; so add another 32 loops for
environmental and process variation.

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

arch/arm/plat-omap/include/mach/sram.h

@@ -24,7 +24,7 @@ extern u32 omap2_set_prcm(u32 dpll_ctrl_val, u32 sdrc_rfr_val, int bypass);
 extern u32 omap3_configure_core_dpll(u32 sdrc_rfr_ctrl,
 				     u32 sdrc_actim_ctrla,
 				     u32 sdrc_actim_ctrlb, u32 m2,
-				     u32 unlock_dll);
+				     u32 unlock_dll, u32 f);
 
 /* Do not use these */
 extern void omap1_sram_reprogram_clock(u32 ckctl, u32 dpllctl);
@@ -62,7 +62,7 @@ extern unsigned long omap243x_sram_reprogram_sdrc_sz;
 extern u32 omap3_sram_configure_core_dpll(u32 sdrc_rfr_ctrl,
 					  u32 sdrc_actim_ctrla,
 					  u32 sdrc_actim_ctrlb, u32 m2,
-					  u32 unlock_dll);
+					  u32 unlock_dll, u32 f);
 extern unsigned long omap3_sram_configure_core_dpll_sz;
 
 #endif