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 <roman.li@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c

@@ -754,6 +754,35 @@ union igp_info {
 	struct _ATOM_INTEGRATED_SYSTEM_INFO_V1_9 info_9;
 };
 
+/*
+ * Return vram width from integrated system info table, if available,
+ * or 0 if not.
+ */
+int amdgpu_atombios_get_vram_width(struct amdgpu_device *adev)
+{
+	struct amdgpu_mode_info *mode_info = &adev->mode_info;
+	int index = GetIndexIntoMasterTable(DATA, IntegratedSystemInfo);
+	u16 data_offset, size;
+	union igp_info *igp_info;
+	u8 frev, crev;
+
+	/* get any igp specific overrides */
+	if (amdgpu_atom_parse_data_header(mode_info->atom_context, index, &size,
+				   &frev, &crev, &data_offset)) {
+		igp_info = (union igp_info *)
+			(mode_info->atom_context->bios + data_offset);
+		switch (crev) {
+		case 8:
+		case 9:
+			return igp_info->info_8.ucUMAChannelNumber * 64;
+		default:
+			return 0;
+		}
+	}
+
+	return 0;
+}
+
 static void amdgpu_atombios_get_igp_ss_overrides(struct amdgpu_device *adev,
 						 struct amdgpu_atom_ss *ss,
 						 int id)

drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.h

@@ -148,6 +148,8 @@ int amdgpu_atombios_get_clock_info(struct amdgpu_device *adev);
 
 int amdgpu_atombios_get_gfx_info(struct amdgpu_device *adev);
 
+int amdgpu_atombios_get_vram_width(struct amdgpu_device *adev);
+
 bool amdgpu_atombios_get_asic_ss_info(struct amdgpu_device *adev,
 				      struct amdgpu_atom_ss *ss,
 				      int id, u32 clock);

drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c

@@ -37,6 +37,8 @@
 #include "oss/oss_2_0_d.h"
 #include "oss/oss_2_0_sh_mask.h"
 
+#include "amdgpu_atombios.h"
+
 static void gmc_v7_0_set_gart_funcs(struct amdgpu_device *adev);
 static void gmc_v7_0_set_irq_funcs(struct amdgpu_device *adev);
 static int gmc_v7_0_wait_for_idle(void *handle);
@@ -325,6 +327,8 @@ static void gmc_v7_0_mc_program(struct amdgpu_device *adev)
  */
 static int gmc_v7_0_mc_init(struct amdgpu_device *adev)
 {
+	adev->mc.vram_width = amdgpu_atombios_get_vram_width(adev);
+	if (!adev->mc.vram_width) {
 		u32 tmp;
 		int chansize, numchan;
 
@@ -367,6 +371,7 @@ static int gmc_v7_0_mc_init(struct amdgpu_device *adev)
 			break;
 		}
 		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);

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);
@@ -487,6 +489,8 @@ static void gmc_v8_0_mc_program(struct amdgpu_device *adev)
  */
 static int gmc_v8_0_mc_init(struct amdgpu_device *adev)
 {
+	adev->mc.vram_width = amdgpu_atombios_get_vram_width(adev);
+	if (!adev->mc.vram_width) {
 		u32 tmp;
 		int chansize, numchan;
 
@@ -529,6 +533,7 @@ static int gmc_v8_0_mc_init(struct amdgpu_device *adev)
 			break;
 		}
 		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);