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[PATCH 01/16] arm64: Use arch_timer_get_rate when trapping CNTFRQ_EL0

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  [PATCH 01/16] arm64: Use arch_timer_get_rate when trapping CNTFRQ_EL0 Marc Zyngier <marc.zyngier@arm.com> - 2017-07-21 19:20 +0200

#1693881 — [PATCH 01/16] arm64: Use arch_timer_get_rate when trapping CNTFRQ_EL0

In an ideal world, CNTFRQ_EL0 always contains the timer frequency
for the kernel to use. Sadly, we get quite a few broken systems
where the firmware authors cannot be bothered to program that
register on all CPUs, and rely on DT to provide that frequency.

So when trapping CNTFRQ_EL0, make sure to return the actual rate
(as known by the kernel), and not CNTFRQ_EL0.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 arch/arm64/kernel/traps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index c7c7088097be..b02295673216 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -519,7 +519,7 @@ static void cntfrq_read_handler(unsigned int esr, struct pt_regs *regs)
 {
 	int rt = (esr & ESR_ELx_SYS64_ISS_RT_MASK) >> ESR_ELx_SYS64_ISS_RT_SHIFT;
 
-	pt_regs_write_reg(regs, rt, read_sysreg(cntfrq_el0));
+	pt_regs_write_reg(regs, rt, arch_timer_get_rate());
 	regs->pc += 4;
 }
 
-- 
2.11.0

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