[PATCH] ARM: 2650/1: PXA27x sleep - workaround Errata 39 & 50 (Patch 2667)

Patch from Jeff Lackey

This patch updates arch/arm/mach-pxa/sleep.S to support
the PXA270 CPU.  It works around Errata 39 & 50 from the
Intel(R) PXA27x Processor Family Specification Update.

Signed-off-by: Jeff Lackey
Signed-off-by: Russell King

arch/arm/mach-pxa/sleep.S

@@ -18,6 +18,11 @@
 
 #include <asm/arch/pxa-regs.h>
 
+#ifdef CONFIG_PXA27x			// workaround for Errata 50
+#define MDREFR_KDIV	0x200a4000	// all banks
+#define CCCR_SLEEP	0x00000107	// L=7 2N=2 A=0 PPDIS=0 CPDIS=0
+#endif
+
 		.text
 
 /*
@@ -28,7 +33,9 @@
 
 ENTRY(pxa_cpu_suspend)
 
+#ifndef CONFIG_IWMMXT
 	mra	r2, r3, acc0
+#endif
 	stmfd	sp!, {r2 - r12, lr}		@ save registers on stack
 
 	@ get coprocessor registers
@@ -61,14 +68,23 @@ ENTRY(pxa_cpu_suspend)
 	@ prepare value for sleep mode
 	mov	r1, #3				@ sleep mode
 
-	@ prepare to put SDRAM into self-refresh manually
-	ldr	r4, =MDREFR
-	ldr	r5, [r4]
-	orr	r5, r5, #MDREFR_SLFRSH
-
 	@ prepare pointer to physical address 0 (virtual mapping in generic.c)
 	mov	r2, #UNCACHED_PHYS_0
 
+	@ prepare SDRAM refresh settings
+	ldr	r4, =MDREFR
+	ldr	r5, [r4]
+
+	@ enable SDRAM self-refresh mode
+	orr	r5, r5, #MDREFR_SLFRSH
+
+#ifdef CONFIG_PXA27x
+	@ set SDCLKx divide-by-2 bits (this is part of a workaround for Errata 50)
+	ldr	r6, =MDREFR_KDIV
+	orr	r5, r5, r6
+#endif
+
+#ifdef CONFIG_PXA25x
 	@ Intel PXA255 Specification Update notes problems
 	@ about suspending with PXBus operating above 133MHz
 	@ (see Errata 31, GPIO output signals, ... unpredictable in sleep
@@ -100,6 +116,18 @@ ENTRY(pxa_cpu_suspend)
 	mov	r0, #0
 	mcr	p14, 0, r0, c6, c0, 0
 	orr	r0, r0, #2			@ initiate change bit
+#endif
+#ifdef CONFIG_PXA27x
+	@ Intel PXA270 Specification Update notes problems sleeping
+	@ with core operating above 91 MHz
+	@ (see Errata 50, ...processor does not exit from sleep...)
+
+	ldr	r6, =CCCR
+	ldr	r8, [r6]		@ keep original value for resume
+
+	ldr	r7, =CCCR_SLEEP		@ prepare CCCR sleep value
+	mov	r0, #0x2		@ prepare value for CLKCFG
+#endif
 
 	@ align execution to a cache line
 	b	1f
@@ -111,6 +139,7 @@ ENTRY(pxa_cpu_suspend)
 	@ All needed values are now in registers.
 	@ These last instructions should be in cache
 
+#if defined(CONFIG_PXA25x) || defined(CONFIG_PXA27x)
 	@ initiate the frequency change...
 	str	r7, [r6]
 	mcr	p14, 0, r0, c6, c0, 0
@@ -118,14 +147,27 @@ ENTRY(pxa_cpu_suspend)
 	@ restore the original cpu speed value for resume
 	str	r8, [r6]
 
-	@ put SDRAM into self-refresh
+	@ need 6 13-MHz cycles before changing PWRMODE
-	str	r5, [r4]
+	@ just set frequency to 91-MHz... 6*91/13 = 42
+
+	mov	r0, #42
+10:	subs	r0, r0, #1
+	bne	10b
+#endif
+
+	@ Do not reorder...
+	@ Intel PXA270 Specification Update notes problems performing
+	@ external accesses after SDRAM is put in self-refresh mode
+	@ (see Errata 39 ...hangs when entering self-refresh mode)
 
 	@ force address lines low by reading at physical address 0
 	ldr	r3, [r2]
 
+	@ put SDRAM into self-refresh
+	str	r5, [r4]
+
 	@ enter sleep mode
-	mcr	p14, 0, r1, c7, c0, 0
+	mcr	p14, 0, r1, c7, c0, 0		@ PWRMODE
 
 20:	b	20b				@ loop waiting for sleep
 
@@ -188,7 +230,9 @@ resume_after_mmu:
 	bl	cpu_xscale_proc_init
 #endif
 	ldmfd	sp!, {r2, r3}
+#ifndef CONFIG_IWMMXT
 	mar	acc0, r2, r3
+#endif
 	ldmfd	sp!, {r4 - r12, pc}		@ return to caller