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authorWill Deacon <will.deacon@arm.com>2011-11-14 17:24:58 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2011-12-09 08:52:25 -0800
commit341f278d7bfbe7233438a8512d183d62ddfae34e (patch)
treec22524b513fb146f44760a4d7a28f2903e1fd050
parent0443648aa178dbf8090edfd6dc54f31f916a174b (diff)
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ARM: 7161/1: errata: no automatic store buffer drain
commit 11ed0ba1754841316d4095478944300acf19acc3 upstream. This patch implements a workaround for PL310 erratum 769419. On revisions of the PL310 prior to r3p2, the Store Buffer does not automatically drain. This can cause normal, non-cacheable writes to be retained when the memory system is idle, leading to suboptimal I/O performance for drivers using coherent DMA. This patch adds an optional wmb() call to the cpu_idle loop. On systems with an outer cache, this causes an explicit flush of the store buffer. Acked-by: Catalin Marinas <catalin.marinas@arm.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--arch/arm/Kconfig12
-rw-r--r--arch/arm/kernel/process.c3
2 files changed, 15 insertions, 0 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 91c84cb..2456bad 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1312,6 +1312,18 @@ config ARM_ERRATA_764369
relevant cache maintenance functions and sets a specific bit
in the diagnostic control register of the SCU.
+config PL310_ERRATA_769419
+ bool "PL310 errata: no automatic Store Buffer drain"
+ depends on CACHE_L2X0
+ help
+ On revisions of the PL310 prior to r3p2, the Store Buffer does
+ not automatically drain. This can cause normal, non-cacheable
+ writes to be retained when the memory system is idle, leading
+ to suboptimal I/O performance for drivers using coherent DMA.
+ This option adds a write barrier to the cpu_idle loop so that,
+ on systems with an outer cache, the store buffer is drained
+ explicitly.
+
endmenu
menu "Kernel Features"
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 5e1e541..74ae833 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -191,6 +191,9 @@ void cpu_idle(void)
#endif
local_irq_disable();
+#ifdef CONFIG_PL310_ERRATA_769419
+ wmb();
+#endif
if (hlt_counter) {
local_irq_enable();
cpu_relax();