drm/amdgpu: add workaround for S3 issues on some vega10 boards

Certain MC registers need a delay after writing them to properly
update in the init sequence.

Signed-off-by: Ken Wang <Ken.Wang@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.h

@@ -1687,6 +1687,8 @@ struct amdgpu_device {
 	bool has_hw_reset;
 	u8				reset_magic[AMDGPU_RESET_MAGIC_NUM];
 
+	/* record last mm index being written through WREG32*/
+	unsigned long last_mm_index;
 };
 
 static inline struct amdgpu_device *amdgpu_ttm_adev(struct ttm_bo_device *bdev)

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

@@ -129,6 +129,10 @@ void amdgpu_mm_wreg(struct amdgpu_device *adev, uint32_t reg, uint32_t v,
 {
 	trace_amdgpu_mm_wreg(adev->pdev->device, reg, v);
 
+	if (adev->asic_type >= CHIP_VEGA10 && reg == 0) {
+		adev->last_mm_index = v;
+	}
+
 	if (!(acc_flags & AMDGPU_REGS_NO_KIQ) && amdgpu_sriov_runtime(adev)) {
 		BUG_ON(in_interrupt());
 		return amdgpu_virt_kiq_wreg(adev, reg, v);
@@ -144,6 +148,10 @@ void amdgpu_mm_wreg(struct amdgpu_device *adev, uint32_t reg, uint32_t v,
 		writel(v, ((void __iomem *)adev->rmmio) + (mmMM_DATA * 4));
 		spin_unlock_irqrestore(&adev->mmio_idx_lock, flags);
 	}
+
+	if (adev->asic_type >= CHIP_VEGA10 && reg == 1 && adev->last_mm_index == 0x5702C) {
+		udelay(500);
+	}
 }
 
 u32 amdgpu_io_rreg(struct amdgpu_device *adev, u32 reg)
@@ -158,6 +166,9 @@ u32 amdgpu_io_rreg(struct amdgpu_device *adev, u32 reg)
 
 void amdgpu_io_wreg(struct amdgpu_device *adev, u32 reg, u32 v)
 {
+	if (adev->asic_type >= CHIP_VEGA10 && reg == 0) {
+		adev->last_mm_index = v;
+	}
 
 	if ((reg * 4) < adev->rio_mem_size)
 		iowrite32(v, adev->rio_mem + (reg * 4));
@@ -165,6 +176,10 @@ void amdgpu_io_wreg(struct amdgpu_device *adev, u32 reg, u32 v)
 		iowrite32((reg * 4), adev->rio_mem + (mmMM_INDEX * 4));
 		iowrite32(v, adev->rio_mem + (mmMM_DATA * 4));
 	}
+
+	if (adev->asic_type >= CHIP_VEGA10 && reg == 1 && adev->last_mm_index == 0x5702C) {
+		udelay(500);
+	}
 }
 
 /**