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Subject[PATCH] ARC: fix broken noncoherent cache ops
Date
All DMA devices on ARC haven't worked with SW cache control
since commit a8eb92d02dd7 ("arc: fix arc_dma_{map,unmap}_page")
This happens because we don't check direction argument at all in
new implementation. Fix that.

Fixies: commit a8eb92d02dd7 ("arc: fix arc_dma_{map,unmap}_page")
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
---
NOTE:
* This patch was stress tested on HSDK with bonie++ (usb and sdio)
with IOC disabled. The ethernet wasn't tested because it doesn't
work with SW cache control as for today (see STAR 9001336019)

arch/arc/mm/dma.c | 46 ++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 44 insertions(+), 2 deletions(-)

diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
index 8c1071840979..cefb776a99ff 100644
--- a/arch/arc/mm/dma.c
+++ b/arch/arc/mm/dma.c
@@ -129,14 +129,56 @@ 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
+ *
+ * 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;
+
+ case DMA_FROM_DEVICE:
+ case DMA_BIDIRECTIONAL:
+ dma_cache_inv(paddr, size);
+ break;
+
+ default:
+ break;
+ }
}
--
2.14.4
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