Modern processors may need to drain the WB before WFI

Since WFI may cause the processor to enter a low-power mode, data may
still be in the write buffer. This patch adds a DSB (or DWB) to the
cpu_(v6|v7)_do_idle functions before the WFI.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm/mm/proc-v6.S b/arch/arm/mm/proc-v6.S
index 294943b..f0cc599 100644 (file)
--- a/arch/arm/mm/proc-v6.S
+++ b/arch/arm/mm/proc-v6.S
@@ -71,6 +71,8 @@ ENTRY(cpu_v6_reset)
  *     IRQs are already disabled.
  */
 ENTRY(cpu_v6_do_idle)
+       mov     r1, #0
+       mcr     p15, 0, r1, c7, c10, 4          @ DWB - WFI may enter a low-power mode
        mcr     p15, 0, r1, c7, c0, 4           @ wait for interrupt
        mov     pc, lr
 

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 721b7d5..0e11d97 100644 (file)
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -63,6 +63,7 @@ ENDPROC(cpu_v7_reset)
  *     IRQs are already disabled.
  */
 ENTRY(cpu_v7_do_idle)
+       dsb                                     @ WFI may enter a low-power mode
        wfi
        mov     pc, lr
 ENDPROC(cpu_v7_do_idle)