drm/amd/amdgpu: add info about vram and gtt max allocation size

Signed-off-by: Junwei Zhang <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

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

···
 				    min((size_t)size, sizeof(vram_gtt_total)))
 				    ? -EFAULT : 0;
 	}
+	case AMDGPU_INFO_VRAM_GTT_MAX: {
+		struct drm_amdgpu_info_vram_gtt_max vram_gtt_max;
+		u64 max_size;
+
+		max_size = adev->mc.real_vram_size - adev->vram_pin_size;
+		vram_gtt_max.vram_max_size = max_size * 3 / 4;
+
+		max_size = adev->mc.visible_vram_size - (adev->vram_pin_size -
+				adev->invisible_pin_size);
+		vram_gtt_max.vram_cpu_accessible_max_size = max_size * 3 / 4;
+
+		max_size = adev->mc.gtt_size - adev->gart_pin_size;
+		vram_gtt_max.gtt_max_size = max_size * 3 / 4;
+
+		return copy_to_user(out, &vram_gtt_max,
+				    min((size_t)size, sizeof(vram_gtt_max)))
+				    ? -EFAULT : 0;
+	}
 	case AMDGPU_INFO_READ_MMR_REG: {
 		unsigned n, alloc_size;
 		uint32_t *regs;

include/uapi/drm/amdgpu_drm.h

···
 #define AMDGPU_INFO_NUM_EVICTIONS		0x18
 /* Query the total size of VRAM and GTT domains */
 #define AMDGPU_INFO_VRAM_GTT_TOTAL		0x19
+/* Query the max allocation size of VRAM and GTT domains */
+#define AMDGPU_INFO_VRAM_GTT_MAX		0x1a
 
 #define AMDGPU_INFO_MMR_SE_INDEX_SHIFT	0
 #define AMDGPU_INFO_MMR_SE_INDEX_MASK	0xff
···
 	__u64 vram_total_size;
 	__u64 vram_cpu_accessible_total_size;
 	__u64 gtt_total_size;
+};
+
+struct drm_amdgpu_info_vram_gtt_max {
+	__u64 vram_max_size;
+	__u64 vram_cpu_accessible_max_size;
+	__u64 gtt_max_size;
 };
 
 struct drm_amdgpu_info_firmware {