OMAP3 SRAM: clear the SDRC PWRENA bit during SDRC frequency change

Clear the SDRC_POWER.PWRENA bit before putting the SDRAM into self-refresh
mode.  This prevents the SDRC from attempting to power off the SDRAM,
which can cause the system to hang.

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

diff --git a/arch/arm/mach-omap2/sram34xx.S b/arch/arm/mach-omap2/sram34xx.S
index 8d524f3..9a45415 100644 (file)
--- a/arch/arm/mach-omap2/sram34xx.S
+++ b/arch/arm/mach-omap2/sram34xx.S
@@ -77,7 +77,9 @@ lock_dll:
 sdram_in_selfrefresh:
        ldr     r4, omap3_sdrc_power    @ read the SDRC_POWER register
        ldr     r5, [r4]                @ read the contents of SDRC_POWER
+       mov     r9, r5                  @ keep a copy of SDRC_POWER bits
        orr     r5, r5, #0x40           @ enable self refresh on idle req
+       bic     r5, r5, #0x4            @ clear PWDENA
        str     r5, [r4]                @ write back to SDRC_POWER register
        ldr     r5, [r4]                @ posted-write barrier for SDRC
        ldr     r4, omap3_cm_iclken1_core       @ read the CM_ICLKEN1_CORE reg
@@ -128,10 +130,9 @@ wait_sdrc_idle1:
        and     r5, r5, #0x2
        cmp     r5, #0
        bne     wait_sdrc_idle1
+restore_sdrc_power_val:
        ldr     r4, omap3_sdrc_power
-       ldr     r5, [r4]
-       bic     r5, r5, #0x40
-       str     r5, [r4]
+       str     r9, [r4]                @ restore SDRC_POWER, no barrier needed
        bx      lr
 wait_dll_lock:
        ldr     r4, omap3_sdrc_dlla_status