drm/msm/a6xx: Use genpd notifier to ensure cx-gdsc collapse

As per the recommended recovery sequence of adreno gpu, cx gdsc should
collapse at hardware before it is turned back ON. This helps to clear
out the stale states in hardware before it is reinitialized. Use the
genpd notifier along with the newly introduced
dev_pm_genpd_synced_poweroff() api to ensure that cx gdsc has collapsed
before we turn it back ON.

Signed-off-by: Akhil P Oommen <[e-mail]>
Reviewed-by: Ulf Hansson <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/516472/
Link: https://lore.kernel.org/r/20230102161757.v5.5.I9e10545c6a448d5eb1b734839b871d1b3146dac3@changeid
Signed-off-by: Rob Clark <[e-mail]>

drivers/gpu/drm/msm/Kconfig

···
 	select SYNC_FILE
 	select PM_OPP
 	select NVMEM
+	select PM_GENERIC_DOMAINS
 	help
 	  DRM/KMS driver for MSM/snapdragon.
 

drivers/gpu/drm/msm/adreno/a6xx_gmu.c

···
 	gmu->initialized = false;
 }
 
+static int cxpd_notifier_cb(struct notifier_block *nb,
+			unsigned long action, void *data)
+{
+	struct a6xx_gmu *gmu = container_of(nb, struct a6xx_gmu, pd_nb);
+
+	if (action == GENPD_NOTIFY_OFF)
+		complete_all(&gmu->pd_gate);
+
+	return 0;
+}
+
 int a6xx_gmu_init(struct a6xx_gpu *a6xx_gpu, struct device_node *node)
 {
 	struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
···
 		ret = -ENODEV;
 		goto detach_cxpd;
 	}
+
+	init_completion(&gmu->pd_gate);
+	complete_all(&gmu->pd_gate);
+	gmu->pd_nb.notifier_call = cxpd_notifier_cb;
 
 	/*
 	 * Get a link to the GX power domain to reset the GPU in case of GMU

drivers/gpu/drm/msm/adreno/a6xx_gmu.h

···
 #ifndef _A6XX_GMU_H_
 #define _A6XX_GMU_H_
 
+#include <linux/completion.h>
 #include <linux/iopoll.h>
 #include <linux/interrupt.h>
+#include <linux/notifier.h>
 #include "msm_drv.h"
 #include "a6xx_hfi.h"
 
···
 	bool initialized;
 	bool hung;
 	bool legacy; /* a618 or a630 */
+
+	/* For power domain callback */
+	struct notifier_block pd_nb;
+	struct completion pd_gate;
 };
 
 static inline u32 gmu_read(struct a6xx_gmu *gmu, u32 offset)

drivers/gpu/drm/msm/adreno/a6xx_gpu.c

···
 
 #include <linux/bitfield.h>
 #include <linux/devfreq.h>
+#include <linux/pm_domain.h>
 #include <linux/soc/qcom/llcc-qcom.h>
 
 #define GPU_PAS_ID 13
···
 {
 	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
 	struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
+	struct a6xx_gmu *gmu = &a6xx_gpu->gmu;
 	int i, active_submits;
 
 	adreno_dump_info(gpu);
···
 	 */
 	gpu->active_submits = 0;
 
+	reinit_completion(&gmu->pd_gate);
+	dev_pm_genpd_add_notifier(gmu->cxpd, &gmu->pd_nb);
+	dev_pm_genpd_synced_poweroff(gmu->cxpd);
+
 	/* Drop the rpm refcount from active submits */
 	if (active_submits)
 		pm_runtime_put(&gpu->pdev->dev);
 
 	/* And the final one from recover worker */
 	pm_runtime_put_sync(&gpu->pdev->dev);
+
+	if (!wait_for_completion_timeout(&gmu->pd_gate, msecs_to_jiffies(1000)))
+		DRM_DEV_ERROR(&gpu->pdev->dev, "cx gdsc didn't collapse\n");
+
+	dev_pm_genpd_remove_notifier(gmu->cxpd);
 
 	pm_runtime_use_autosuspend(&gpu->pdev->dev);