From b4ed9f86df441d7ac304f70cc711c257e7c8ebf1 Mon Sep 17 00:00:00 2001 From: Fabio Estevam Date: Wed, 11 Mar 2015 17:12:12 -0300 Subject: [PATCH] mx6: Set shared override bit in PL310 AUX_CTRL register Having bit 22 cleared in the PL310 Auxiliary Control register (shared attribute override enable) has the side effect of transforming Normal Shared Non-cacheable reads into Cacheable no-allocate reads. Coherent DMA buffers in Linux always have a Cacheable alias via the kernel linear mapping and the processor can speculatively load cache lines into the PL310 controller. With bit 22 cleared, Non-cacheable reads would unexpectedly hit such cache lines leading to buffer corruption. This was inspired by a patch from Catalin Marinas [1] and also from recent discussions in the linux-arm-kernel list [2] where Russell King and Rob Herring suggested that bootloaders should initialize the cache. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2010-November/031810.html [2] https://lkml.org/lkml/2015/2/20/199 Signed-off-by: Fabio Estevam Acked-by: Catalin Marinas --- arch/arm/cpu/armv7/mx6/soc.c | 8 ++++++++ arch/arm/include/asm/pl310.h | 2 ++ 2 files changed, 10 insertions(+) diff --git a/arch/arm/cpu/armv7/mx6/soc.c b/arch/arm/cpu/armv7/mx6/soc.c index dd34138896..21ef9d0573 100644 --- a/arch/arm/cpu/armv7/mx6/soc.c +++ b/arch/arm/cpu/armv7/mx6/soc.c @@ -523,6 +523,14 @@ void v7_outer_cache_enable(void) struct pl310_regs *const pl310 = (struct pl310_regs *)L2_PL310_BASE; unsigned int val; + + /* + * Set bit 22 in the auxiliary control register. If this bit + * is cleared, PL310 treats Normal Shared Non-cacheable + * accesses as Cacheable no-allocate. + */ + setbits_le32(&pl310->pl310_aux_ctrl, L310_SHARED_ATT_OVERRIDE_ENABLE); + #if defined CONFIG_MX6SL struct iomuxc *iomux = (struct iomuxc *)IOMUXC_BASE_ADDR; val = readl(&iomux->gpr[11]); diff --git a/arch/arm/include/asm/pl310.h b/arch/arm/include/asm/pl310.h index ddc245bfd5..de7650eae7 100644 --- a/arch/arm/include/asm/pl310.h +++ b/arch/arm/include/asm/pl310.h @@ -16,6 +16,8 @@ #define L2X0_STNDBY_MODE_EN (1 << 0) #define L2X0_CTRL_EN 1 +#define L310_SHARED_ATT_OVERRIDE_ENABLE (1 << 22) + struct pl310_regs { u32 pl310_cache_id; u32 pl310_cache_type; -- 2.25.1