drm/amdgpu: fix modprobe failure of the secondary GPU when GDDR6 training enabled(V5)

[why]
In dual GPUs scenario, stolen_size is assigned to zero on the secondary GPU,
since there is no pre-OS console using that memory. Then the bottom region of
VRAM was allocated as GTT, unfortunately a small region of bottom VRAM was
encroached by UMC firmware during GDDR6 BIST training, this cause page fault.

[how]
Forcing stolen_size to 3MB, then the bottom region of VRAM was
allocated as stolen memory, GTT corruption avoid.
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Tianci.Yin <tianci.yin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -60,6 +60,11 @@
  */
 #define AMDGPU_GMC_FAULT_TIMEOUT	5000ULL
 
+/*
+ * Default stolen memory size, 1024 * 768 * 4
+ */
+#define AMDGPU_STOLEN_BIST_TRAINING_DEFAULT_SIZE	0x300000ULL
+
 struct firmware;
 
 /*

drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c

@@ -640,7 +640,12 @@ static int gmc_v10_0_late_init(void *handle)
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
 	int r;
 
-	amdgpu_bo_late_init(adev);
+	/*
+	 * Can't free the stolen VGA memory when it might be used for memory
+	 * training again.
+	 */
+	if (!adev->fw_vram_usage.mem_train_support)
+		amdgpu_bo_late_init(adev);
 
 	r = amdgpu_gmc_allocate_vm_inv_eng(adev);
 	if (r)
@@ -824,6 +829,19 @@ static int gmc_v10_0_sw_init(void *handle)
 
 	adev->gmc.stolen_size = gmc_v10_0_get_vbios_fb_size(adev);
 
+	/*
+	 * In dual GPUs scenario, stolen_size is assigned to zero on the
+	 * secondary GPU, since there is no pre-OS console using that memory.
+	 * Then the bottom region of VRAM was allocated as GTT, unfortunately a
+	 * small region of bottom VRAM was encroached by UMC firmware during
+	 * GDDR6 BIST training, this cause page fault.
+	 * The page fault can be fixed by forcing stolen_size to 3MB, then the
+	 * bottom region of VRAM was allocated as stolen memory, GTT corruption
+	 * avoid.
+	 */
+	adev->gmc.stolen_size = max(adev->gmc.stolen_size,
+				    AMDGPU_STOLEN_BIST_TRAINING_DEFAULT_SIZE);
+
 	/* Memory manager */
 	r = amdgpu_bo_init(adev);
 	if (r)
@@ -863,6 +881,13 @@ static void gmc_v10_0_gart_fini(struct amdgpu_device *adev)
 static int gmc_v10_0_sw_fini(void *handle)
 {
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
+	void *stolen_vga_buf;
+
+	/*
+	 * Free the stolen memory if it wasn't already freed in late_init
+	 * because of memory training.
+	 */
+	amdgpu_bo_free_kernel(&adev->stolen_vga_memory, NULL, &stolen_vga_buf);
 
 	amdgpu_vm_manager_fini(adev);
 	gmc_v10_0_gart_fini(adev);