[PATCH v2 1/3] drm/amdgpu: use pitch and surface offset for GMC v7/v8 fb size

[Richard Lane <richardlanedev@gmail.com>]

gmc_v7_0_get_vbios_fb_size() and gmc_v8_0_get_vbios_fb_size() currently
calculate the pre-OS framebuffer reservation as VIEWPORT_WIDTH *
VIEWPORT_HEIGHT * 4, assuming the scanout stride matches the viewport
width and that the surface starts at offset 0 of VRAM.

On Apple 27" 5K iMacs, EFI initializes a single 2560x2880 viewport at
boot but allocates a 5120-pixel stride surface (mmGRPH_PITCH = 5120)
and places mmGRPH_PRIMARY_SURFACE_ADDRESS at a 3 MiB offset (0x300000)
from vram_start, spanning [3 MiB, 59.25 MiB) in VRAM. Reserving only
2560 * 2880 * 4 bytes allows permanent TTM driver BOs to overlap the
active scanout and corrupt the boot splash screen.

Calculate the reservation size using mmGRPH_PITCH instead of
VIEWPORT_WIDTH and add the mmGRPH_PRIMARY_SURFACE_ADDRESS offset from
vram_start so the full active pre-OS scanout region is preserved.

Signed-off-by: Richard Lane <richardlanedev@gmail.com>
---
 drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c | 8 +++++---
 drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c | 8 +++++---
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
index c09f5153679e..00704dbfc1bb 100644
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
@@ -929,9 +929,11 @@ static unsigned int gmc_v7_0_get_vbios_fb_size(struct amdgpu_device *adev)
 	} else {
 		u32 viewport = RREG32(mmVIEWPORT_SIZE);
 
-		size = (REG_GET_FIELD(viewport, VIEWPORT_SIZE, VIEWPORT_HEIGHT) *
-			REG_GET_FIELD(viewport, VIEWPORT_SIZE, VIEWPORT_WIDTH) *
-			4);
+		size = REG_GET_FIELD(viewport, VIEWPORT_SIZE, VIEWPORT_HEIGHT) *
+		       RREG32(mmGRPH_PITCH) * 4;
+		if (size)
+			size += RREG32(mmGRPH_PRIMARY_SURFACE_ADDRESS) -
+				lower_32_bits(adev->gmc.vram_start);
 	}
 
 	return size;
diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
index 15592027e7c0..a64a3cc07858 100644
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
@@ -1037,9 +1037,11 @@ static unsigned int gmc_v8_0_get_vbios_fb_size(struct amdgpu_device *adev)
 	} else {
 		u32 viewport = RREG32(mmVIEWPORT_SIZE);
 
-		size = (REG_GET_FIELD(viewport, VIEWPORT_SIZE, VIEWPORT_HEIGHT) *
-			REG_GET_FIELD(viewport, VIEWPORT_SIZE, VIEWPORT_WIDTH) *
-			4);
+		size = REG_GET_FIELD(viewport, VIEWPORT_SIZE, VIEWPORT_HEIGHT) *
+		       RREG32(mmGRPH_PITCH) * 4;
+		if (size)
+			size += RREG32(mmGRPH_PRIMARY_SURFACE_ADDRESS) -
+				lower_32_bits(adev->gmc.vram_start);
 	}
 
 	return size;
-- 
2.55.0