linux-kernel - [PATCH] nouveau: remove bogus uses of DMA_ATTR_SKIP_CPU

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Date:   Wed,  3 Jul 2019 13:35:13 -0700
From:   Christoph Hellwig <hch@....de>
To:     bskeggs@...hat.com
Cc:     jglisse@...hat.com, nouveau@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] nouveau: remove bogus uses of DMA_ATTR_SKIP_CPU_SYNC

DMA_ATTR_SKIP_CPU_SYNC should only be used when the driver manually
performs dma cache maintainance operations using the dma_sync_*
calls.  Nouveau doesn't do that, and generally just assumes DMA
is coherent.  Use plain dma_map_page which doesn't make this code
correct but at least a little less wrong and simpler.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 drivers/gpu/drm/nouveau/nouveau_dmem.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index b9ced2e61667..a5d9b537cbaf 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -186,9 +186,8 @@ nouveau_dmem_fault_alloc_and_copy(struct vm_area_struct *vma,
 		}
 
 		fault->dma[fault->npages] =
-			dma_map_page_attrs(dev, dpage, 0, PAGE_SIZE,
-					   PCI_DMA_BIDIRECTIONAL,
-					   DMA_ATTR_SKIP_CPU_SYNC);
+			dma_map_page(dev, dpage, 0, PAGE_SIZE,
+				     PCI_DMA_BIDIRECTIONAL);
 		if (dma_mapping_error(dev, fault->dma[fault->npages])) {
 			dst_pfns[i] = MIGRATE_PFN_ERROR;
 			__free_page(dpage);
@@ -706,9 +705,8 @@ nouveau_dmem_migrate_alloc_and_copy(struct vm_area_struct *vma,
 		}
 
 		migrate->dma[migrate->dma_nr] =
-			dma_map_page_attrs(dev, spage, 0, PAGE_SIZE,
-					   PCI_DMA_BIDIRECTIONAL,
-					   DMA_ATTR_SKIP_CPU_SYNC);
+			dma_map_page(dev, spage, 0, PAGE_SIZE,
+				     PCI_DMA_BIDIRECTIONAL);
 		if (dma_mapping_error(dev, migrate->dma[migrate->dma_nr])) {
 			nouveau_dmem_page_free_locked(drm, dpage);
 			dst_pfns[i] = 0;
-- 
2.20.1