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Subject[PATCH v6 08/24] arm64: Unmask PMR before going idle
Date
CPU does not received signals for interrupts with a priority masked by
ICC_PMR_EL1. This means the CPU might not come back from a WFI
instruction.

Make sure ICC_PMR_EL1 does not mask interrupts when doing a WFI.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
---
arch/arm64/mm/proc.S | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 2c75b0b..3c7064c 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -20,6 +20,7 @@

#include <linux/init.h>
#include <linux/linkage.h>
+#include <linux/irqchip/arm-gic-v3.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
#include <asm/hwcap.h>
@@ -53,10 +54,27 @@
* cpu_do_idle()
*
* Idle the processor (wait for interrupt).
+ *
+ * If the CPU supports priority masking we must do additional work to
+ * ensure that interrupts are not masked at the PMR (because the core will
+ * not wake up if we block the wake up signal in the interrupt controller).
*/
ENTRY(cpu_do_idle)
+alternative_if_not ARM64_HAS_IRQ_PRIO_MASKING
+ dsb sy // WFI may enter a low-power mode
+ wfi
+ ret
+alternative_else
+ mrs x0, daif // save I bit
+ msr daifset, #2 // set I bit
+ mrs_s x1, SYS_ICC_PMR_EL1 // save PMR
+alternative_endif
+ mov x2, #GIC_PRIO_IRQON
+ msr_s SYS_ICC_PMR_EL1, x2 // unmask PMR
dsb sy // WFI may enter a low-power mode
wfi
+ msr_s SYS_ICC_PMR_EL1, x1 // restore PMR
+ msr daif, x0 // restore I bit
ret
ENDPROC(cpu_do_idle)

--
1.9.1
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