From: Will Deacon Date: Mon, 14 Nov 2011 16:24:58 +0000 (+0100) Subject: ARM: 7161/1: errata: no automatic store buffer drain X-Git-Tag: v2.6.32.50~24 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=b94342e75946ed88a3048602390633b9f047d5f2;p=linux-pvops.git 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 Tested-by: Marc Zyngier Signed-off-by: Will Deacon Signed-off-by: Russell King Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index e516aa23af0f..b68faef7ca0c 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1332,6 +1332,18 @@ config ATAGS_PROC Should the atags used to boot the kernel be exported in an "atags" file in procfs. Useful with kexec. +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 "CPU Power Management" diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 0d96d0171c05..61f90d390547 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -156,6 +156,9 @@ void cpu_idle(void) #endif local_irq_disable(); +#ifdef CONFIG_PL310_ERRATA_769419 + wmb(); +#endif if (hlt_counter) { local_irq_enable(); cpu_relax();