drm/amdgpu: fixup bad vram size on gmc v8

Some boards(like RX550) seem to have garbage in the upper
16 bits of the vram size register.  Check for
this and clamp the size properly.  Fixes
boards reporting bogus amounts of vram.

after add this patch,the maximum GPU VRAM size is 64GB,
otherwise only 64GB vram size will be used.

Signed-off-by: Zongmin Zhou<zhouzongmin@kylinos.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
index 492ebed2915be44d92c285fd14fc95d30b7d27c0..63b890f1e8afb8159978af0fa7eb6b9665ad3a8e 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
@@ -515,10 +515,10 @@ static void gmc_v8_0_mc_program(struct amdgpu_device *adev)
 static int gmc_v8_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 */
@@ -562,8 +562,15 @@ static int gmc_v8_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);