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authorRussell King <rmk@dyn-67.arm.linux.org.uk>2007-10-27 11:01:35 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2007-10-31 15:21:40 +0000
commit0214f9221aa06fba35c0cd5c80641b0fcfcb1cbe (patch)
tree7cf9e67f6acec67b7e9d84768c8fc8821f636162 /arch/arm
parent[ARM] Fix pxamci regression (diff)
downloadlinux-dev-0214f9221aa06fba35c0cd5c80641b0fcfcb1cbe.tar.xz
linux-dev-0214f9221aa06fba35c0cd5c80641b0fcfcb1cbe.zip
[ARM] Fix FIQ issue with ARM926
Jon Eibertzon writes: > We have noticed that the I-cache is disabled while waiting for > interrupt in cpu_arm926_do_idle in arch/arm/mm/proc-arm926.S > and we are curious to know why, because this causes us a great > performance hit when executing in FIQ-handlers. Is it assumed > here that every individual FIQ-handler re-enables the I-cache? The I-cache disable is an errata workaround, so the solution is to disable FIQs across the section with the I-cache disabled. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/mm/proc-arm926.S4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm/mm/proc-arm926.S b/arch/arm/mm/proc-arm926.S
index 5b80b6bdd0cb..194ef48968e6 100644
--- a/arch/arm/mm/proc-arm926.S
+++ b/arch/arm/mm/proc-arm926.S
@@ -105,9 +105,13 @@ ENTRY(cpu_arm926_do_idle)
mrc p15, 0, r1, c1, c0, 0 @ Read control register
mcr p15, 0, r0, c7, c10, 4 @ Drain write buffer
bic r2, r1, #1 << 12
+ mrs r3, cpsr @ Disable FIQs while Icache
+ orr ip, r3, #PSR_F_BIT @ is disabled
+ msr cpsr_c, ip
mcr p15, 0, r2, c1, c0, 0 @ Disable I cache
mcr p15, 0, r0, c7, c0, 4 @ Wait for interrupt
mcr p15, 0, r1, c1, c0, 0 @ Restore ICache enable
+ msr cpsr_c, r3 @ Restore FIQ state
mov pc, lr
/*