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drm/amdgpu: Add comments to gmc structure 

Explain fields like aper_base, agp_start etc. The definition
of those fields are confusing as they are from different view
(CPU or GPU). Add comments for easier understand.

Signed-off-by: Oak Zeng <Oak.Zeng@amd.com>
Reviewed-by: Alex Deucher <Alex.Deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Oak Zeng 2019-11-06 11:18:54 -06:00 committed by Alex Deucher
parent ef177d11d6
commit f6baa07497
1 changed files with 30 additions and 0 deletions
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30
drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
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@ -127,18 +127,48 @@ struct amdgpu_xgmi {
};
struct amdgpu_gmc {
/* FB's physical address in MMIO space (for CPU to
* map FB). This is different compared to the agp/
* gart/vram_start/end field as the later is from
* GPU's view and aper_base is from CPU's view.
*/
resource_size_t aper_size;
resource_size_t aper_base;
/* for some chips with <= 32MB we need to lie
* about vram size near mc fb location */
u64 mc_vram_size;
u64 visible_vram_size;
/* AGP aperture start and end in MC address space
* Driver find a hole in the MC address space
* to place AGP by setting MC_VM_AGP_BOT/TOP registers
* Under VMID0, logical address == MC address. AGP
* aperture maps to physical bus or IOVA addressed.
* AGP aperture is used to simulate FB in ZFB case.
* AGP aperture is also used for page table in system
* memory (mainly for APU).
*
*/
u64 agp_size;
u64 agp_start;
u64 agp_end;
/* GART aperture start and end in MC address space
* Driver find a hole in the MC address space
* to place GART by setting VM_CONTEXT0_PAGE_TABLE_START/END_ADDR
* registers
* Under VMID0, logical address inside GART aperture will
* be translated through gpuvm gart page table to access
* paged system memory
*/
u64 gart_size;
u64 gart_start;
u64 gart_end;
/* Frame buffer aperture of this GPU device. Different from
* fb_start (see below), this only covers the local GPU device.
* Driver get fb_start from MC_VM_FB_LOCATION_BASE (set by vbios)
* and calculate vram_start of this local device by adding an
* offset inside the XGMI hive.
* Under VMID0, logical address == MC address
*/
u64 vram_start;
u64 vram_end;
/* FB region , it's same as local vram region in single GPU, in XGMI