drm/amdgpu/ctx: only reset stable pstate if the user changed it (v2)

Check if the requested stable pstate matches the current one before
changing it.  This avoids changing the stable pstate on context
destroy if the user never changed it in the first place via the
IOCTL.

v2: compare the current and requested rather than setting a flag (Lijo)

Fixes: 8cda7a4f ("drm/amdgpu/UAPI: add new CTX OP to get/set stable pstates")
Reviewed-by: NLijo Lazar <lijo.lazar@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

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

@@ -296,6 +296,7 @@ static int amdgpu_ctx_set_stable_pstate(struct amdgpu_ctx *ctx,
 {
 	struct amdgpu_device *adev = ctx->adev;
 	enum amd_dpm_forced_level level;
+	u32 current_stable_pstate;
 	int r;
 
 	mutex_lock(&adev->pm.stable_pstate_ctx_lock);
@@ -304,6 +305,10 @@ static int amdgpu_ctx_set_stable_pstate(struct amdgpu_ctx *ctx,
 		goto done;
 	}
 
+	r = amdgpu_ctx_get_stable_pstate(ctx, &current_stable_pstate);
+	if (r || (stable_pstate == current_stable_pstate))
+		goto done;
+
 	switch (stable_pstate) {
 	case AMDGPU_CTX_STABLE_PSTATE_NONE:
 		level = AMD_DPM_FORCED_LEVEL_AUTO;