[PATCH] drm/amdgpu: fix modprobe failure of the 2nd GPU when GDDR6 training enabled

[Tianci Yin]

From: "Tianci.Yin" <tianci.yin at amd.com>

[why]
In dual GPUs scenario, stolen_size is assigned to zero on the 2nd GPU,
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 pagefault.

[how]
Forcing stolen_size to 3MB, then the bottom region of VRAM was
allocated as stolen memory, GTT corruption avoid.
The stolen memory of the 2nd GPU will be free in late_init phase,
no memory wasted.

Change-Id: Icd0ad7de41333282949bb1e3e676c6c307ddd081
Signed-off-by: Tianci.Yin <tianci.yin at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h |  6 ++++++
 drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c  | 21 +++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
index c91dd602d5f1..440b793316df 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
+++ b/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_VGA_DEFAULT_SIZE	0x300000
+
 struct firmware;
 
 /*
@@ -192,6 +197,7 @@ struct amdgpu_gmc {
 	uint32_t                srbm_soft_reset;
 	bool			prt_warning;
 	uint64_t		stolen_size;
+	bool			stolen_temp_reserved;
 	/* apertures */
 	u64			shared_aperture_start;
 	u64			shared_aperture_end;
diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c
index 7dc8c068c62a..0c96b67d6ca7 100644
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c
@@ -566,6 +566,11 @@ static int gmc_v10_0_late_init(void *handle)
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
 	int r;
 
+	if (adev->gmc.stolen_temp_reserved) {
+		amdgpu_bo_late_init(adev);
+		adev->gmc.stolen_temp_reserved = false;
+	}
+
 	r = amdgpu_gmc_allocate_vm_inv_eng(adev);
 	if (r)
 		return r;
@@ -756,6 +761,22 @@ static int gmc_v10_0_sw_init(void *handle)
 		return r;
 
 	adev->gmc.stolen_size = gmc_v10_0_get_vbios_fb_size(adev);
+	/*
+	 * In dual GPUs scenario, stolen_size is assigned to zero on the 2nd GPU,
+	 * 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 pagefault.
+	 * 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.
+	 * The stolen memory of the 2nd GPU will be free in late_init phase,
+	 * no memory wasted.
+	 */
+	if (adev->fw_vram_usage.mem_train_support &&
+		adev->gmc.stolen_size == 0) {
+		adev->gmc.stolen_size = AMDGPU_STOLEN_VGA_DEFAULT_SIZE;
+		adev->gmc.stolen_temp_reserved = true;
+	} else
+		adev->gmc.stolen_temp_reserved = false;
 
 	/* Memory manager */
 	r = amdgpu_bo_init(adev);
-- 
2.17.1