[PATCH v2] drm/amdgpu: add safeguards for querying GMC CG state

[Lang Yu]

We observed a GPU hang when querying GMC CG state(i.e.,
cat amdgpu_pm_info) on cyan skillfish. Acctually, cyan
skillfish doesn't support any CG features.

Only allow ASICs which support GMC CG features accessing
related registers. As some ASICs support GMC CG but cg_flags
are not set. Use GC IP version instead of cg_flags to
determine whether GMC CG is supported or not.

v2:
 - Use a function to encapsulate more functionality.(Christian)
 - Use IP verion to determine whether CG is supported or not.(Lijo)

Signed-off-by: Lang Yu <Lang.Yu at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c | 10 ++++++++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h |  1 +
 drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c  |  3 +++
 drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c   |  3 +++
 drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c   |  3 +++
 5 files changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
index d426de48d299..be1f03b02af6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
@@ -876,3 +876,13 @@ int amdgpu_gmc_vram_checking(struct amdgpu_device *adev)
 
 	return 0;
 }
+
+bool amdgpu_gmc_cg_enabled(struct amdgpu_device *adev)
+{
+	switch (adev->ip_versions[GC_HWIP][0]) {
+	case IP_VERSION(10, 1, 3):
+		return false;
+	default:
+		return true;
+	}
+}
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
index 93505bb0a36c..b916e73c7de1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
@@ -338,4 +338,5 @@ uint64_t amdgpu_gmc_vram_mc2pa(struct amdgpu_device *adev, uint64_t mc_addr);
 uint64_t amdgpu_gmc_vram_pa(struct amdgpu_device *adev, struct amdgpu_bo *bo);
 uint64_t amdgpu_gmc_vram_cpu_pa(struct amdgpu_device *adev, struct amdgpu_bo *bo);
 int amdgpu_gmc_vram_checking(struct amdgpu_device *adev);
+bool amdgpu_gmc_cg_enabled(struct amdgpu_device *adev);
 #endif
diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c
index 73ab0eebe4e2..4e46f618d6c1 100644
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c
@@ -1156,6 +1156,9 @@ static void gmc_v10_0_get_clockgating_state(void *handle, u32 *flags)
 {
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
 
+	if (!amdgpu_gmc_cg_enabled(adev))
+		return;
+
 	adev->mmhub.funcs->get_clockgating(adev, flags);
 
 	if (adev->ip_versions[ATHUB_HWIP][0] >= IP_VERSION(2, 1, 0))
diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
index ca9841d5669f..ff9dff2a6cf1 100644
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
@@ -1695,6 +1695,9 @@ static void gmc_v8_0_get_clockgating_state(void *handle, u32 *flags)
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
 	int data;
 
+	if (!amdgpu_gmc_cg_enabled(adev))
+		return;
+
 	if (amdgpu_sriov_vf(adev))
 		*flags = 0;
 
diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c
index 4595027a8c63..faf017609dfe 100644
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c
@@ -1952,6 +1952,9 @@ static void gmc_v9_0_get_clockgating_state(void *handle, u32 *flags)
 {
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
 
+	if (!amdgpu_gmc_cg_enabled(adev))
+		return;
+
 	adev->mmhub.funcs->get_clockgating(adev, flags);
 
 	athub_v1_0_get_clockgating(adev, flags);
-- 
2.25.1