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authorEugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>2018-07-24 17:13:02 +0300
committerVineet Gupta <vgupta@synopsys.com>2018-07-27 13:12:40 -0700
commit4c612add7b18844ddd733ebdcbe754520155999b (patch)
tree9e21f86905d7924adb22b75512fe4fecf4a2d086 /arch/arc/mm
parent6d20caed9b92d0db005324281e10bb9fd4813a32 (diff)
ARC: dma [non IOC]: fix arc_dma_sync_single_for_(device|cpu)
ARC backend for dma_sync_single_for_(device|cpu) was broken as it was not honoring the @dir argument and simply forcing it based on the call: - arc_dma_sync_single_for_device(dir) assumed DMA_TO_DEVICE (cache wback) - arc_dma_sync_single_for_cpu(dir) assumed DMA_FROM_DEVICE (cache inv) This is not true given the DMA API programming model and has been discussed here [1] in some detail. Interestingly while the deficiency has been there forever, it only started showing up after 4.17 dma common ops rework, commit a8eb92d02dd7 ("arc: fix arc_dma_{map,unmap}_page") which wired up these calls under the more commonly used dma_map_page API triggering the issue. [1]: https://lkml.org/lkml/2018/5/18/979 Fixes: commit a8eb92d02dd7 ("arc: fix arc_dma_{map,unmap}_page") Cc: stable@kernel.org # v4.17+ Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com> Signed-off-by: Vineet Gupta <vgupta@synopsys.com> [vgupta: reworked changelog]
Diffstat (limited to 'arch/arc/mm')
-rw-r--r--arch/arc/mm/dma.c49
1 files changed, 47 insertions, 2 deletions
diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
index 8c1071840979..ec47e6079f5d 100644
--- a/arch/arc/mm/dma.c
+++ b/arch/arc/mm/dma.c
@@ -129,14 +129,59 @@ int arch_dma_mmap(struct device *dev, struct vm_area_struct *vma,
return ret;
}
+/*
+ * Cache operations depending on function and direction argument, inspired by
+ * https://lkml.org/lkml/2018/5/18/979
+ * "dma_sync_*_for_cpu and direction=TO_DEVICE (was Re: [PATCH 02/20]
+ * dma-mapping: provide a generic dma-noncoherent implementation)"
+ *
+ * | map == for_device | unmap == for_cpu
+ * |----------------------------------------------------------------
+ * TO_DEV | writeback writeback | none none
+ * FROM_DEV | invalidate invalidate | invalidate* invalidate*
+ * BIDIR | writeback+inv writeback+inv | invalidate invalidate
+ *
+ * [*] needed for CPU speculative prefetches
+ *
+ * NOTE: we don't check the validity of direction argument as it is done in
+ * upper layer functions (in include/linux/dma-mapping.h)
+ */
+
void arch_sync_dma_for_device(struct device *dev, phys_addr_t paddr,
size_t size, enum dma_data_direction dir)
{
- dma_cache_wback(paddr, size);
+ switch (dir) {
+ case DMA_TO_DEVICE:
+ dma_cache_wback(paddr, size);
+ break;
+
+ case DMA_FROM_DEVICE:
+ dma_cache_inv(paddr, size);
+ break;
+
+ case DMA_BIDIRECTIONAL:
+ dma_cache_wback_inv(paddr, size);
+ break;
+
+ default:
+ break;
+ }
}
void arch_sync_dma_for_cpu(struct device *dev, phys_addr_t paddr,
size_t size, enum dma_data_direction dir)
{
- dma_cache_inv(paddr, size);
+ switch (dir) {
+ case DMA_TO_DEVICE:
+ break;
+
+ /* FROM_DEVICE invalidate needed if speculative CPU prefetch only */
+ case DMA_FROM_DEVICE:
+ case DMA_BIDIRECTIONAL:
+ dma_cache_inv(paddr, size);
+ break;
+
+ default:
+ break;
+ }
}