gpu: nvgpu: gpu railgate handling with runtime pm

Earlier implementation of railgate disable config is disabling
runtime pm during pm_init. This is causing multiple issues:
1. gpu rail will be on as soon as nvgpu driver probe is called.
   Actual gpu hw init may happen at much later point of time.
2. This is breaking railgate_enable sysfs node functionality.
   railgate_enable is not working if runtime pm is disabled.

To avoid all these issues for railgate disable, enable runtime pm
during pm_init and set auto-suspend delay to negative (-1), which
will disable runtime pm suspend calls.

Also fixed following issues along with this:
1. Updated railgate_enable debugfs implementation to use auto-suspend delay.
   To disable railgating:
   Set auto-suspend delay with negative value(-1) which will disable runtime
   pm suspend.
   To enable railgating:
   Set auto-suspend delay with railgate_delay value.
   Also removed redundant user_railgate_disabled gk20a device data and
   replaced with can_railgate, where ever it is applicable.
2. Initialized default railgate_delay to 500msec to avoid railgate
   on/off transitions with railigate enable from disabled state.
3. Created railgate_residency debug fs node irrespective of can_railgate
   initial state. This is helping with the case, where initial state of
   railgate state off and then railgate enable is done through sysfs node.

Bug 2073029

Change-Id: I531da6d93ba8907e806f65a1de2a447c1ec2665c
Signed-off-by: seshendra Gadagottu <sgadagottu@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1694944
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

drivers/gpu/nvgpu/common/linux/debug.c

@@ -267,9 +267,6 @@ static int gk20a_railgating_debugfs_init(struct gk20a *g)
 	struct nvgpu_os_linux *l = nvgpu_os_linux_from_gk20a(g);
 	struct dentry *d;
 
-	if (!g->can_railgate)
-		return 0;
-
 	d = debugfs_create_file(
 		"railgate_residency", S_IRUGO|S_IWUSR, l->debugfs, g,
 						&railgate_residency_fops);

drivers/gpu/nvgpu/common/linux/driver_common.c

@@ -168,8 +168,12 @@ static void nvgpu_init_pm_vars(struct gk20a *g)
 	g->ptimer_src_freq = platform->ptimer_src_freq;
 	g->support_pmu = support_gk20a_pmu(dev_from_gk20a(g));
 	g->can_railgate = platform->can_railgate_init;
-	g->railgate_delay = platform->railgate_delay_init;
 	g->ldiv_slowdown_factor = platform->ldiv_slowdown_factor_init;
+	/* if default delay is not set, set default delay to 500msec */
+	if (platform->railgate_delay_init)
+		g->railgate_delay = platform->railgate_delay_init;
+	else
+		g->railgate_delay = NVGPU_DEFAULT_RAILGATE_IDLE_TIMEOUT;
 	__nvgpu_set_enabled(g, NVGPU_PMU_PERFMON, platform->enable_perfmon);
 
 	/* set default values to aelpg parameters */

drivers/gpu/nvgpu/common/linux/module.c

@@ -458,10 +458,10 @@ int __gk20a_do_idle(struct gk20a *g, bool force_reset)
 	 * If User disables rail gating, we take one more
 	 * extra refcount
 	 */
-	if (g->user_railgate_disabled)
-		target_ref_cnt = 2;
-	else
+	if (g->can_railgate)
 		target_ref_cnt = 1;
+	else
+		target_ref_cnt = 2;
 	nvgpu_mutex_acquire(&platform->railgate_lock);
 
 	nvgpu_timeout_init(g, &timeout, GK20A_WAIT_FOR_IDLE_MS,
@@ -964,7 +964,7 @@ static int gk20a_pm_suspend(struct device *dev)
 	struct gk20a_platform *platform = dev_get_drvdata(dev);
 	struct gk20a *g = get_gk20a(dev);
 	int ret = 0;
-	int idle_usage_count = g->user_railgate_disabled ? 1 : 0;
+	int idle_usage_count = 0;
 
 	if (!g->power_on) {
 		if (!pm_runtime_enabled(dev))
@@ -1020,23 +1020,19 @@ static int gk20a_pm_init(struct device *dev)
 
 	nvgpu_log_fn(g, " ");
 
-	/* Initialise pm runtime */
-	if (g->railgate_delay) {
+	/*
+	 * Initialise pm runtime. For railgate disable
+	 * case, set autosuspend delay to negative which
+	 * will suspend runtime pm
+	 */
+	if (g->railgate_delay && g->can_railgate)
 		pm_runtime_set_autosuspend_delay(dev,
 				 g->railgate_delay);
-		pm_runtime_use_autosuspend(dev);
-	}
+	else
+		pm_runtime_set_autosuspend_delay(dev, -1);
 
-	if (g->can_railgate) {
-		pm_runtime_enable(dev);
-		if (!pm_runtime_enabled(dev))
-			gk20a_pm_unrailgate(dev);
-		else
-			gk20a_pm_railgate(dev);
-	} else {
-		__pm_runtime_disable(dev, false);
-		gk20a_pm_unrailgate(dev);
-	}
+	pm_runtime_use_autosuspend(dev);
+	pm_runtime_enable(dev);
 
 	return err;
 }

drivers/gpu/nvgpu/common/linux/sysfs.c

@@ -305,24 +305,23 @@ static ssize_t railgate_enable_store(struct device *dev,
 	unsigned long railgate_enable = 0;
 	/* dev is guaranteed to be valid here. Ok to de-reference */
 	struct gk20a *g = get_gk20a(dev);
-	int err = 0;
+	int err;
 
 	if (kstrtoul(buf, 10, &railgate_enable) < 0)
 		return -EINVAL;
 
 	if (railgate_enable && !g->can_railgate) {
-		/* release extra ref count */
-		gk20a_idle(g);
 		g->can_railgate = true;
-		g->user_railgate_disabled = false;
+		pm_runtime_set_autosuspend_delay(dev, g->railgate_delay);
 	} else if (railgate_enable == 0 && g->can_railgate) {
-		/* take extra ref count */
-		err = gk20a_busy(g);
-		if (err)
-			return err;
 		g->can_railgate = false;
-		g->user_railgate_disabled = true;
+		pm_runtime_set_autosuspend_delay(dev, -1);
 	}
+	/* wake-up system to make rail-gating setting effective */
+	err = gk20a_busy(g);
+	if (err)
+		return err;
+	gk20a_idle(g);
 
 	nvgpu_info(g, "railgate is %s.", g->can_railgate ?
 		"enabled" : "disabled");

drivers/gpu/nvgpu/gk20a/gk20a.c

@@ -370,9 +370,6 @@ int gk20a_wait_for_idle(struct gk20a *g)
 	if (!g)
 		return -ENODEV;
 
-	if (g->user_railgate_disabled)
-		target_usage_count = 1;
-
 	while ((nvgpu_atomic_read(&g->usage_count) != target_usage_count)
 			&& (wait_length-- >= 0))
 		nvgpu_msleep(20);

drivers/gpu/nvgpu/gk20a/gk20a.h

@@ -1358,7 +1358,6 @@ struct gk20a {
 	u32 ptimer_src_freq;
 
 	bool can_railgate;
-	bool user_railgate_disabled;
 	int railgate_delay;
 	u8 ldiv_slowdown_factor;
 	unsigned int aggressive_sync_destroy_thresh;

drivers/gpu/nvgpu/include/nvgpu/defaults.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, NVIDIA CORPORATION.  All rights reserved.
+ * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -28,4 +28,6 @@
  */
 #define NVGPU_DEFAULT_GR_IDLE_TIMEOUT	3000
 
+#define NVGPU_DEFAULT_RAILGATE_IDLE_TIMEOUT 500
+
 #endif