OMAP2/3 SDRC: don't set SDRC_POWER.PWDENA on boot

Stop setting SDRC_POWER.PWDENA on boot.  There is a nasty erratum
(34xx erratum 1.150) that can cause memory corruption if PWDENA is
enabled.

Based originally on a patch from Samu P. Onkalo <samu.p.onkalo@nokia.com>.

Tested on BeagleBoard rev C2.
Signed-off-by: NPaul Walmsley <paul@pwsan.com>
Cc: Samu P. Onkalo <samu.p.onkalo@nokia.com>

arch/arm/mach-omap2/sdrc.c

@@ -125,8 +125,11 @@ void __init omap2_sdrc_init(struct omap_sdrc_params *sdrc_cs0,
 	sdrc_init_params_cs1 = sdrc_cs1;
 
 	/* XXX Enable SRFRONIDLEREQ here also? */
+	/*
+	 * PWDENA should not be set due to 34xx erratum 1.150 - PWDENA
+	 * can cause random memory corruption
+	 */
 	l = (1 << SDRC_POWER_EXTCLKDIS_SHIFT) |
-		(1 << SDRC_POWER_PWDENA_SHIFT) |
 		(1 << SDRC_POWER_PAGEPOLICY_SHIFT);
 	sdrc_write_reg(l, SDRC_POWER);
 }

arch/arm/mach-omap2/sram34xx.S

@@ -58,7 +58,6 @@
 
 /* SDRC_POWER bit settings */
 #define SRFRONIDLEREQ_MASK		0x40
-#define PWDENA_MASK			0x4
 
 /* CM_IDLEST1_CORE bit settings */
 #define ST_SDRC_MASK			0x2
@@ -160,7 +159,6 @@ sdram_in_selfrefresh:
 	ldr	r12, [r11]		@ read the contents of SDRC_POWER
 	mov	r9, r12			@ keep a copy of SDRC_POWER bits
 	orr 	r12, r12, #SRFRONIDLEREQ_MASK	@ enable self refresh on idle
-	bic 	r12, r12, #PWDENA_MASK	@ clear PWDENA
 	str 	r12, [r11]		@ write back to SDRC_POWER register
 	ldr	r12, [r11]		@ posted-write barrier for SDRC
 idle_sdrc: