[PATCH 2/7] drm/gpusvm: use more selective dma dir in get_pages()

[Matthew Auld]

If we are only reading the memory then from the device pov the direction
can be DMA_TO_DEVICE. This aligns with the xe-userptr code. Using the
most restrictive data direction to represent the access is normally a
good idea.

Signed-off-by: Matthew Auld <matthew.a...@intel.com>
Cc: Thomas Hellström <thomas.hellst...@linux.intel.com>
Cc: Matthew Brost <matthew.br...@intel.com>
---
 drivers/gpu/drm/drm_gpusvm.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index 48993cef4a74..7f1cf5492bba 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -1355,6 +1355,8 @@ int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
        int err = 0;
        struct dev_pagemap *pagemap;
        struct drm_pagemap *dpagemap;
+       enum dma_data_direction dma_dir = ctx->read_only ? DMA_TO_DEVICE :
+                                                          DMA_BIDIRECTIONAL;
 
 retry:
        hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
@@ -1459,7 +1461,7 @@ int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
                                dpagemap->ops->device_map(dpagemap,
                                                          gpusvm->drm->dev,
                                                          page, order,
-                                                         DMA_BIDIRECTIONAL);
+                                                         dma_dir);
                        if (dma_mapping_error(gpusvm->drm->dev,
                                              range->dma_addr[j].addr)) {
                                err = -EFAULT;
@@ -1478,7 +1480,7 @@ int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
                        addr = dma_map_page(gpusvm->drm->dev,
                                            page, 0,
                                            PAGE_SIZE << order,
-                                           DMA_BIDIRECTIONAL);
+                                           dma_dir);
                        if (dma_mapping_error(gpusvm->drm->dev, addr)) {
                                err = -EFAULT;
                                goto err_unmap;
@@ -1486,7 +1488,7 @@ int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
 
                        range->dma_addr[j] = drm_pagemap_device_addr_encode
                                (addr, DRM_INTERCONNECT_SYSTEM, order,
-                                DMA_BIDIRECTIONAL);
+                                dma_dir);
                }
                i += 1 << order;
                num_dma_mapped = i;
-- 
2.48.1