linux-kernel - [PATCH] drm/ttm: only use DMA32 if needed for dummy_read

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Message-ID: <tencent_0B319B215E8D487CC082C0DA5E8E46B86B08@qq.com>
Date: Tue, 16 Jan 2024 15:24:06 +0800
From: Yangyu Chen <cyy@...self.name>
To: dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Cc: Christian Koenig <christian.koenig@....com>,
	Huang Rui <ray.huang@....com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Jiuyang Liu <liu@...yang.me>,
	Yichuan Gao <i@...is.me>,
	Yangyu Chen <cyy@...self.name>
Subject: [PATCH] drm/ttm: only use DMA32 if needed for dummy_read_page

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 <cyy@...self.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