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: v3.0.13~62 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=341f278d7bfbe7233438a8512d183d62ddfae34e;p=karo-tx-linux.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 91c84cbefcf2..2456badc8634 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 5e1e54197227..74ae833e5c7d 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();