drm/msm: Add support for GPU cooling

Register GPU as a devfreq cooling device so that it can be passively
cooled by the thermal framework.
Signed-off-by: Akhil P Oommen <akhilpo@codeaurora.org>
Tested-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/msm_gpu.c

@@ -14,6 +14,7 @@
 #include <generated/utsrelease.h>
 #include <linux/string_helpers.h>
 #include <linux/devfreq.h>
+#include <linux/devfreq_cooling.h>
 #include <linux/devcoredump.h>
 #include <linux/sched/task.h>
 
@@ -107,9 +108,18 @@ static void msm_devfreq_init(struct msm_gpu *gpu)
 	if (IS_ERR(gpu->devfreq.devfreq)) {
 		DRM_DEV_ERROR(&gpu->pdev->dev, "Couldn't initialize GPU devfreq\n");
 		gpu->devfreq.devfreq = NULL;
+		return;
 	}
 
 	devfreq_suspend_device(gpu->devfreq.devfreq);
+
+	gpu->cooling = of_devfreq_cooling_register(gpu->pdev->dev.of_node,
+			gpu->devfreq.devfreq);
+	if (IS_ERR(gpu->cooling)) {
+		DRM_DEV_ERROR(&gpu->pdev->dev,
+				"Couldn't register GPU cooling device\n");
+		gpu->cooling = NULL;
+	}
 }
 
 static int enable_pwrrail(struct msm_gpu *gpu)
@@ -1044,4 +1054,6 @@ void msm_gpu_cleanup(struct msm_gpu *gpu)
 	if (gpu->worker) {
 		kthread_destroy_worker(gpu->worker);
 	}
+
+	devfreq_cooling_unregister(gpu->cooling);
 }

drivers/gpu/drm/msm/msm_gpu.h

@@ -155,6 +155,8 @@ struct msm_gpu {
 	struct msm_gpu_state *crashstate;
 	/* True if the hardware supports expanded apriv (a650 and newer) */
 	bool hw_apriv;
+
+	struct thermal_cooling_device *cooling;
 };
 
 static inline struct msm_gpu *dev_to_gpu(struct device *dev)