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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 08:54:13 -0800
commit03c371b70411f1f2805e2965eff0629908b59c13 (patch)
treed52e1790be765d4aeab937d6c400aeb98bbf4895
parente9b529a3d8929c793ed6326d407ec7bf18bff6bb (diff)
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 3146ed3f6eca..dfe01400cd14 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1297,6 +1297,18 @@ 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
source "arch/arm/common/Kconfig"
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 1a347f481e5e..c9d11eaf4384 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -192,6 +192,9 @@ void cpu_idle(void)
#endif
local_irq_disable();
+#ifdef CONFIG_PL310_ERRATA_769419
+ wmb();
+#endif
if (hlt_counter) {
local_irq_enable();
cpu_relax();