[PATCH] drm/amdgpu: Fixup bad vram size on gmc v6 and v7

[Qiang Ma <maqianga@xxxxxxxxxxxxx>]

Some boards(like Oland PRO: 0x1002:0x6613) seem to have
garbage in the upper 16 bits of the vram size register,
kern log as follows:

[    6.000000] [drm] Detected VRAM RAM=2256537600M, BAR=256M
[    6.007812] [drm] RAM width 64bits GDDR5
[    6.031250] [drm] amdgpu: 2256537600M of VRAM memory ready

This is obviously not true, check for this and clamp the size
properly. Fixes boards reporting bogus amounts of vram,
kern log as follows:

[    2.789062] [drm] Probable bad vram size: 0x86800800
[    2.789062] [drm] Detected VRAM RAM=2048M, BAR=256M
[    2.789062] [drm] RAM width 64bits GDDR5
[    2.789062] [drm] amdgpu: 2048M of VRAM memory ready

Signed-off-by: Qiang Ma <maqianga@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c | 11 +++++++++--
 drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c | 13 ++++++++++---
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c
index 23b478639921..3703695f7789 100644
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c
@@ -309,8 +309,15 @@ static int gmc_v6_0_mc_init(struct amdgpu_device *adev)
 	}
 	adev->gmc.vram_width = numchan * chansize;
 	/* size in MB on si */
-	adev->gmc.mc_vram_size = RREG32(mmCONFIG_MEMSIZE) * 1024ULL * 1024ULL;
-	adev->gmc.real_vram_size = RREG32(mmCONFIG_MEMSIZE) * 1024ULL * 1024ULL;
+	tmp = RREG32(mmCONFIG_MEMSIZE);
+	/* some boards may have garbage in the upper 16 bits */
+	if (tmp & 0xffff0000) {
+		DRM_INFO("Probable bad vram size: 0x%08x\n", tmp);
+		if (tmp & 0xffff)
+			tmp &= 0xffff;
+	}
+	adev->gmc.mc_vram_size = tmp * 1024ULL * 1024ULL;
+	adev->gmc.real_vram_size = adev->gmc.mc_vram_size;
 
 	if (!(adev->flags & AMD_IS_APU)) {
 		r = amdgpu_device_resize_fb_bar(adev);
diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
index 3da7b6a2b00d..1df1fc578ff6 100644
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
@@ -316,10 +316,10 @@ static void gmc_v7_0_mc_program(struct amdgpu_device *adev)
 static int gmc_v7_0_mc_init(struct amdgpu_device *adev)
 {
 	int r;
+	u32 tmp;
 
 	adev->gmc.vram_width = amdgpu_atombios_get_vram_width(adev);
 	if (!adev->gmc.vram_width) {
-		u32 tmp;
 		int chansize, numchan;
 
 		/* Get VRAM informations */
@@ -363,8 +363,15 @@ static int gmc_v7_0_mc_init(struct amdgpu_device *adev)
 		adev->gmc.vram_width = numchan * chansize;
 	}
 	/* size in MB on si */
-	adev->gmc.mc_vram_size = RREG32(mmCONFIG_MEMSIZE) * 1024ULL * 1024ULL;
-	adev->gmc.real_vram_size = RREG32(mmCONFIG_MEMSIZE) * 1024ULL * 1024ULL;
+	tmp = RREG32(mmCONFIG_MEMSIZE);
+	/* some boards may have garbage in the upper 16 bits */
+	if (tmp & 0xffff0000) {
+		DRM_INFO("Probable bad vram size: 0x%08x\n", tmp);
+		if (tmp & 0xffff)
+			tmp &= 0xffff;
+	}
+	adev->gmc.mc_vram_size = tmp * 1024ULL * 1024ULL;
+	adev->gmc.real_vram_size = adev->gmc.mc_vram_size;
 
 	if (!(adev->flags & AMD_IS_APU)) {
 		r = amdgpu_device_resize_fb_bar(adev);
-- 
2.20.1