RE: [PATCH] drm/amdgpu: Set ttm caching flags during bo allocation

[Xu, Feifei]

[AMD Official Use Only]

Reviewed-by: Feifei Xu <feifei...@amd.com>

-----Original Message-----
From: amd-gfx <amd-gfx-boun...@lists.freedesktop.org> On Behalf Of Oak Zeng
Sent: Tuesday, June 29, 2021 7:16 AM
To: amd-gfx@lists.freedesktop.org
Cc: Kuehling, Felix <felix.kuehl...@amd.com>; Zhu, James <james....@amd.com>; 
Koenig, Christian <christian.koe...@amd.com>; Zeng, Oak <oak.z...@amd.com>
Subject: [PATCH] drm/amdgpu: Set ttm caching flags during bo allocation

The ttm caching flags (ttm_cached, ttm_write_combined etc) are used to 
determine a buffer object's mapping attributes in both CPU page table and GPU 
page table (when that buffer is also accessed by GPU). Currently the ttm 
caching flags are set in function amdgpu_ttm_io_mem_reserve which is called 
during DRM_AMDGPU_GEM_MMAP ioctl. This has a problem since the GPU mapping of 
the buffer object (ioctl DRM_AMDGPU_GEM_VA) can happen earlier than the mmap 
time, thus the GPU page table update code can't pick up the right ttm caching 
flags to decide the right GPU page table attributes.

This patch moves the ttm caching flags setting to function amdgpu_vram_mgr_new 
- this function is called during the first step of a buffer object create (eg, 
DRM_AMDGPU_GEM_CREATE) so the later both CPU and GPU mapping function calls 
will pick up this flag for CPU/GPU page table set up.

Signed-off-by: Oak Zeng <oak.z...@amd.com>
Suggested-by: Christian Koenig <christian.koe...@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c      | 4 ----
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 5 +++++
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 6297363..93acf6f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -607,10 +607,6 @@ static int amdgpu_ttm_io_mem_reserve(struct ttm_device 
*bdev,

                mem->bus.offset += adev->gmc.aper_base;
                mem->bus.is_iomem = true;
-               if (adev->gmc.xgmi.connected_to_cpu)
-                       mem->bus.caching = ttm_cached;
-               else
-                       mem->bus.caching = ttm_write_combined;
                break;
        default:
                return -EINVAL;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index a52e17e..6cb66eb 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -454,6 +454,11 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager 
*man,
        if (i == 1)
                mem->placement |= TTM_PL_FLAG_CONTIGUOUS;

+       if (adev->gmc.xgmi.connected_to_cpu)
+               mem->bus.caching = ttm_cached;
+       else
+               mem->bus.caching = ttm_write_combined;
+
        atomic64_add(vis_usage, &mgr->vis_usage);
        mem->mm_node = nodes;
        return 0;
--
2.7.4

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