drm/amdgpu: Read vram width from integrated system info table

On KB, KV, CZ we should read the vram width from integrated system
table, if we can. The NOOFCHAN in MC_SHARED_CHMAP is not accurate.

With this change we can enable two 4k displays on CZ again. This use
case was broken sometime in January when we started looking at
vram_width for bandwidth calculations instead of hardcoding this value.

v2:
  Return 0 if integrated system info table is not available.

Tested-by: Roman Li <[email protected]>
Signed-off-by: Harry Wentland <[email protected]>
Reviewed-by: Alex Deucher <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

1 files changed, 45 insertions, 40 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
index d19d1c5e2847..42b2f357a799 100644
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
@@ -38,6 +38,8 @@
 #include "vid.h"
 #include "vi.h"
 
+#include "amdgpu_atombios.h"
+
 
 static void gmc_v8_0_set_gart_funcs(struct amdgpu_device *adev);
 static void gmc_v8_0_set_irq_funcs(struct amdgpu_device *adev);
@@ -487,48 +489,51 @@ static void gmc_v8_0_mc_program(struct amdgpu_device *adev)
  */
 static int gmc_v8_0_mc_init(struct amdgpu_device *adev)
 {
-	u32 tmp;
-	int chansize, numchan;
+	adev->mc.vram_width = amdgpu_atombios_get_vram_width(adev);
+	if (!adev->mc.vram_width) {
+		u32 tmp;
+		int chansize, numchan;
 
-	/* Get VRAM informations */
-	tmp = RREG32(mmMC_ARB_RAMCFG);
-	if (REG_GET_FIELD(tmp, MC_ARB_RAMCFG, CHANSIZE)) {
-		chansize = 64;
-	} else {
-		chansize = 32;
-	}
-	tmp = RREG32(mmMC_SHARED_CHMAP);
-	switch (REG_GET_FIELD(tmp, MC_SHARED_CHMAP, NOOFCHAN)) {
-	case 0:
-	default:
-		numchan = 1;
-		break;
-	case 1:
-		numchan = 2;
-		break;
-	case 2:
-		numchan = 4;
-		break;
-	case 3:
-		numchan = 8;
-		break;
-	case 4:
-		numchan = 3;
-		break;
-	case 5:
-		numchan = 6;
-		break;
-	case 6:
-		numchan = 10;
-		break;
-	case 7:
-		numchan = 12;
-		break;
-	case 8:
-		numchan = 16;
-		break;
+		/* Get VRAM informations */
+		tmp = RREG32(mmMC_ARB_RAMCFG);
+		if (REG_GET_FIELD(tmp, MC_ARB_RAMCFG, CHANSIZE)) {
+			chansize = 64;
+		} else {
+			chansize = 32;
+		}
+		tmp = RREG32(mmMC_SHARED_CHMAP);
+		switch (REG_GET_FIELD(tmp, MC_SHARED_CHMAP, NOOFCHAN)) {
+		case 0:
+		default:
+			numchan = 1;
+			break;
+		case 1:
+			numchan = 2;
+			break;
+		case 2:
+			numchan = 4;
+			break;
+		case 3:
+			numchan = 8;
+			break;
+		case 4:
+			numchan = 3;
+			break;
+		case 5:
+			numchan = 6;
+			break;
+		case 6:
+			numchan = 10;
+			break;
+		case 7:
+			numchan = 12;
+			break;
+		case 8:
+			numchan = 16;
+			break;
+		}
+		adev->mc.vram_width = numchan * chansize;
 	}
-	adev->mc.vram_width = numchan * chansize;
 	/* Could aper size report 0 ? */
 	adev->mc.aper_base = pci_resource_start(adev->pdev, 0);
 	adev->mc.aper_size = pci_resource_len(adev->pdev, 0);