| From 11ed0ba1754841316d4095478944300acf19acc3 Mon Sep 17 00:00:00 2001 |
| From: Will Deacon <will.deacon@arm.com> |
| Date: Mon, 14 Nov 2011 17:24:58 +0100 |
| Subject: ARM: 7161/1: errata: no automatic store buffer drain |
| |
| From: Will Deacon <will.deacon@arm.com> |
| |
| 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> |
| |
| --- |
| arch/arm/Kconfig | 12 ++++++++++++ |
| arch/arm/kernel/process.c | 3 +++ |
| 2 files changed, 15 insertions(+) |
| |
| --- 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" |
| --- 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(); |
