amdgpu/gmc_v9: save/restore sdpif regs during S3

fixes S3 issue with IOMMU + S/G  enabled @ 64M VRAM.
Suggested-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Shirish S <shirish.s@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_gmc.h

@@ -195,6 +195,7 @@ struct amdgpu_gmc {
 	uint32_t                srbm_soft_reset;
 	bool			prt_warning;
 	uint64_t		stolen_size;
+	uint32_t		sdpif_register;
 	/* apertures */
 	u64			shared_aperture_start;
 	u64			shared_aperture_end;

drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c

@@ -1271,6 +1271,19 @@ static void gmc_v9_0_init_golden_registers(struct amdgpu_device *adev)
 	}
 }
 
+/**
+ * gmc_v9_0_restore_registers - restores regs
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * This restores register values, saved at suspend.
+ */
+static void gmc_v9_0_restore_registers(struct amdgpu_device *adev)
+{
+	if (adev->asic_type == CHIP_RAVEN)
+		WREG32(mmDCHUBBUB_SDPIF_MMIO_CNTRL_0, adev->gmc.sdpif_register);
+}
+
 /**
  * gmc_v9_0_gart_enable - gart enable
  *
@@ -1376,6 +1389,20 @@ static int gmc_v9_0_hw_init(void *handle)
 	return r;
 }
 
+/**
+ * gmc_v9_0_save_registers - saves regs
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * This saves potential register values that should be
+ * restored upon resume
+ */
+static void gmc_v9_0_save_registers(struct amdgpu_device *adev)
+{
+	if (adev->asic_type == CHIP_RAVEN)
+		adev->gmc.sdpif_register = RREG32(mmDCHUBBUB_SDPIF_MMIO_CNTRL_0);
+}
+
 /**
  * gmc_v9_0_gart_disable - gart disable
  *
@@ -1412,9 +1439,16 @@ static int gmc_v9_0_hw_fini(void *handle)
 
 static int gmc_v9_0_suspend(void *handle)
 {
+	int r;
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
 
-	return gmc_v9_0_hw_fini(adev);
+	r = gmc_v9_0_hw_fini(adev);
+	if (r)
+		return r;
+
+	gmc_v9_0_save_registers(adev);
+
+	return 0;
 }
 
 static int gmc_v9_0_resume(void *handle)
@@ -1422,6 +1456,7 @@ static int gmc_v9_0_resume(void *handle)
 	int r;
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
 
+	gmc_v9_0_restore_registers(adev);
 	r = gmc_v9_0_hw_init(adev);
 	if (r)
 		return r;

drivers/gpu/drm/amd/include/asic_reg/dce/dce_12_0_offset.h

@@ -7376,6 +7376,8 @@
 #define mmCRTC4_CRTC_DRR_CONTROL                                                                       0x0f3e
 #define mmCRTC4_CRTC_DRR_CONTROL_BASE_IDX                                                              2
 
+#define mmDCHUBBUB_SDPIF_MMIO_CNTRL_0                                                                  0x395d
+#define mmDCHUBBUB_SDPIF_MMIO_CNTRL_0_BASE_IDX                                                         2
 
 // addressBlock: dce_dc_fmt4_dispdec
 // base address: 0x2000