From f6baa07497fbebcc05096097dfd9f32b8caa50b1 Mon Sep 17 00:00:00 2001
From: Oak Zeng <Oak.Zeng@amd.com>
Date: Wed, 6 Nov 2019 11:18:54 -0600
Subject: drm/amdgpu: Add comments to gmc structure
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Git-commit: f6baa07497fbebcc05096097dfd9f32b8caa50b1
Patch-mainline: v5.5-rc1
References: bsc#1152489
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>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h | 30 +++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
index 555d8e57fae9..406736a1bd3d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
@@ -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
--
2.28.0