[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

1 files changed, 50 insertions, 6 deletions

diff --git a/arch/arm/mach-pxa/sleep.S b/arch/arm/mach-pxa/sleep.S
index 16cad2c2497c..5786ccad938c 100644
--- a/arch/arm/mach-pxa/sleep.S
+++ b/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
+        @ 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
 
-        @ prepare pointer to physical address 0 (virtual mapping in generic.c)
-        mov     r2, #UNCACHED_PHYS_0
+#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
-        str     r5, [r4]
+        @ need 6 13-MHz cycles before changing PWRMODE
+        @ 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