From f86f55d3ad21b21b736bdeb29bee0f0937b77138 Mon Sep 17 00:00:00 2001 From: Jim Quinlan Date: Tue, 27 Aug 2013 16:57:51 -0400 Subject: MIPS: DMA: For BMIPS5000 cores flush region just like non-coherent R10000 The BMIPS5000 (Zephyr) processor utilizes instruction speculation. A stale misprediction address in either the JTB or the CRS may trigger a prefetch inside a region that is currently being used by a DMA engine, which is not IO-coherent. This prefetch will fetch a line into the scache, and that line will soon become stale (ie wrong) during/after the DMA. Mayhem ensues. In dma-default.c, the r10000 is handled as a special case in the same way that we want to handle Zephyr. So we generalize the exception cases into a function, and include Zephyr as one of the processors that needs this special care. Signed-off-by: Jim Quinlan Cc: linux-mips@linux-mips.org Cc: cernekee@gmail.com Patchwork: https://patchwork.linux-mips.org/patch/5776/ Signed-off-by: Ralf Baechle --- arch/mips/mm/dma-default.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) (limited to 'arch/mips') diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c index aaccf1c10699..468f7f967f97 100644 --- a/arch/mips/mm/dma-default.c +++ b/arch/mips/mm/dma-default.c @@ -50,16 +50,20 @@ static inline struct page *dma_addr_to_page(struct device *dev, } /* + * The affected CPUs below in 'cpu_needs_post_dma_flush()' can + * speculatively fill random cachelines with stale data at any time, + * requiring an extra flush post-DMA. + * * Warning on the terminology - Linux calls an uncached area coherent; * MIPS terminology calls memory areas with hardware maintained coherency * coherent. */ - -static inline int cpu_is_noncoherent_r10000(struct device *dev) +static inline int cpu_needs_post_dma_flush(struct device *dev) { return !plat_device_is_coherent(dev) && (current_cpu_type() == CPU_R10000 || - current_cpu_type() == CPU_R12000); + current_cpu_type() == CPU_R12000 || + current_cpu_type() == CPU_BMIPS5000); } static gfp_t massage_gfp_flags(const struct device *dev, gfp_t gfp) @@ -230,7 +234,7 @@ static inline void __dma_sync(struct page *page, static void mips_dma_unmap_page(struct device *dev, dma_addr_t dma_addr, size_t size, enum dma_data_direction direction, struct dma_attrs *attrs) { - if (cpu_is_noncoherent_r10000(dev)) + if (cpu_needs_post_dma_flush(dev)) __dma_sync(dma_addr_to_page(dev, dma_addr), dma_addr & ~PAGE_MASK, size, direction); @@ -284,7 +288,7 @@ static void mips_dma_unmap_sg(struct device *dev, struct scatterlist *sg, static void mips_dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle, size_t size, enum dma_data_direction direction) { - if (cpu_is_noncoherent_r10000(dev)) + if (cpu_needs_post_dma_flush(dev)) __dma_sync(dma_addr_to_page(dev, dma_handle), dma_handle & ~PAGE_MASK, size, direction); } @@ -305,7 +309,7 @@ static void mips_dma_sync_sg_for_cpu(struct device *dev, /* Make sure that gcc doesn't leave the empty loop body. */ for (i = 0; i < nelems; i++, sg++) { - if (cpu_is_noncoherent_r10000(dev)) + if (cpu_needs_post_dma_flush(dev)) __dma_sync(sg_page(sg), sg->offset, sg->length, direction); } -- cgit v1.2.3-58-ga151