[PATCH] drm/ttm: only use DMA32 if needed for dummy_read_page

[Yangyu Chen]

Some platforms may not have any memory in ZONE_DMA32 and use IOMMU to allow
32-bit-DMA-only device to work. Forcing GFP_DMA32 on dummy_read_page will
fail in such platforms. Only use DMA32 when it must to get the bug
resolved.

Signed-off-by: Yangyu Chen <c...@cyyself.name>
---
 drivers/gpu/drm/ttm/ttm_device.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index d48b39132b32..62f16fb72428 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -63,7 +63,7 @@ static void ttm_global_release(void)
        mutex_unlock(&ttm_global_mutex);
 }
 
-static int ttm_global_init(void)
+static int ttm_global_init(bool use_dma32)
 {
        struct ttm_global *glob = &ttm_glob;
        unsigned long num_pages, num_dma32;
@@ -95,7 +95,8 @@ static int ttm_global_init(void)
        ttm_pool_mgr_init(num_pages);
        ttm_tt_mgr_init(num_pages, num_dma32);
 
-       glob->dummy_read_page = alloc_page(__GFP_ZERO | GFP_DMA32);
+       glob->dummy_read_page = use_dma32 ? alloc_page(__GFP_ZERO | GFP_DMA32) :
+                                           alloc_page(__GFP_ZERO);
 
        if (unlikely(glob->dummy_read_page == NULL)) {
                ret = -ENOMEM;
@@ -200,7 +201,7 @@ int ttm_device_init(struct ttm_device *bdev, const struct 
ttm_device_funcs *func
        if (WARN_ON(vma_manager == NULL))
                return -EINVAL;
 
-       ret = ttm_global_init();
+       ret = ttm_global_init(use_dma32);
        if (ret)
                return ret;
 
-- 
2.43.0