[PATCH] drm/amdgpu: fix S3 failure on specific platform

[ken.wang at amd.com]

From: Ken Wang <Qingqing.Wang at amd.com>

Change-Id: Ie932508ad6949f8bfc7c8db1f5874d3440d09fc6
Signed-off-by: Ken Wang <Qingqing.Wang at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h        | 3 +++
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index ecc33c4..54c30fe 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -1702,6 +1702,9 @@ struct amdgpu_device {
 	/* record hw reset is performed */
 	bool has_hw_reset;
 
+	/* 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)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 21e504a..24b908c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -124,6 +124,10 @@ 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);
@@ -139,6 +143,10 @@ 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)
-- 
2.7.4