[PATCH 0/3] drm/msm: Improved devfreq tuning

[PATCH 0/3] drm/msm: Improved devfreq tuning

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

This is the outcome of trying to fix some bad gpu freq behavior seen in
some use-cases, in particular mobile games that throttle themselves to
30fps.  With the existing tuning, we'd end up spending most of the time
that we should be running fast at a low freq, and most of the idle time
at a high freq.

First two patches are prep, 3/3 is the interesting bit.  See the patch
description in 3/3 for more details.

Rob Clark (3):
  drm/msm: Split out devfreq handling
  drm/msm: Split out get_freq() helper
  drm/msm: Devfreq tuning

 drivers/gpu/drm/msm/Makefile          |   1 +
 drivers/gpu/drm/msm/adreno/a6xx_gpu.c |   4 +-
 drivers/gpu/drm/msm/msm_gpu.c         | 124 ++--------------
 drivers/gpu/drm/msm/msm_gpu.h         |  27 +++-
 drivers/gpu/drm/msm/msm_gpu_devfreq.c | 203 ++++++++++++++++++++++++++
 5 files changed, 238 insertions(+), 121 deletions(-)
 create mode 100644 drivers/gpu/drm/msm/msm_gpu_devfreq.c

-- 
2.31.1

[PATCH 1/3] drm/msm: Split out devfreq handling

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

Before we start adding more cleverness, split it into it's own file.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/gpu/drm/msm/Makefile          |   1 +
 drivers/gpu/drm/msm/adreno/a6xx_gpu.c |   4 +-
 drivers/gpu/drm/msm/msm_gpu.c         | 116 +---------------------
 drivers/gpu/drm/msm/msm_gpu.h         |  18 ++--
 drivers/gpu/drm/msm/msm_gpu_devfreq.c | 133 ++++++++++++++++++++++++++
 5 files changed, 151 insertions(+), 121 deletions(-)
 create mode 100644 drivers/gpu/drm/msm/msm_gpu_devfreq.c

diff --git a/drivers/gpu/drm/msm/Makefile b/drivers/gpu/drm/msm/Makefile
index 2c00aa70b708..904535eda0c4 100644
--- a/drivers/gpu/drm/msm/Makefile
+++ b/drivers/gpu/drm/msm/Makefile
@@ -90,6 +90,7 @@ msm-y := \
 	msm_gem_submit.o \
 	msm_gem_vma.o \
 	msm_gpu.o \
+	msm_gpu_devfreq.o \
 	msm_iommu.o \
 	msm_perf.o \
 	msm_rd.o \
diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
index a7df02298479..55ea136b8933 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -1477,7 +1477,7 @@ static int a6xx_pm_resume(struct msm_gpu *gpu)
 	if (ret)
 		return ret;
 
-	msm_gpu_resume_devfreq(gpu);
+	msm_devfreq_resume(gpu);
 
 	a6xx_llc_activate(a6xx_gpu);
 
@@ -1494,7 +1494,7 @@ static int a6xx_pm_suspend(struct msm_gpu *gpu)
 
 	a6xx_llc_deactivate(a6xx_gpu);
 
-	devfreq_suspend_device(gpu->devfreq.devfreq);
+	msm_devfreq_suspend(gpu);
 
 	ret = a6xx_gmu_stop(a6xx_gpu);
 	if (ret)
diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
index c4e202f0366c..70d8610b1b73 100644
--- a/drivers/gpu/drm/msm/msm_gpu.c
+++ b/drivers/gpu/drm/msm/msm_gpu.c
@@ -13,8 +13,6 @@
 
 #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>
 
@@ -22,106 +20,6 @@
  * Power Management:
  */
 
-static int msm_devfreq_target(struct device *dev, unsigned long *freq,
-		u32 flags)
-{
-	struct msm_gpu *gpu = dev_to_gpu(dev);
-	struct dev_pm_opp *opp;
-
-	opp = devfreq_recommended_opp(dev, freq, flags);
-
-	if (IS_ERR(opp))
-		return PTR_ERR(opp);
-
-	trace_msm_gpu_freq_change(dev_pm_opp_get_freq(opp));
-
-	if (gpu->funcs->gpu_set_freq)
-		gpu->funcs->gpu_set_freq(gpu, opp);
-	else
-		clk_set_rate(gpu->core_clk, *freq);
-
-	dev_pm_opp_put(opp);
-
-	return 0;
-}
-
-static int msm_devfreq_get_dev_status(struct device *dev,
-		struct devfreq_dev_status *status)
-{
-	struct msm_gpu *gpu = dev_to_gpu(dev);
-	ktime_t time;
-
-	if (gpu->funcs->gpu_get_freq)
-		status->current_frequency = gpu->funcs->gpu_get_freq(gpu);
-	else
-		status->current_frequency = clk_get_rate(gpu->core_clk);
-
-	status->busy_time = gpu->funcs->gpu_busy(gpu);
-
-	time = ktime_get();
-	status->total_time = ktime_us_delta(time, gpu->devfreq.time);
-	gpu->devfreq.time = time;
-
-	return 0;
-}
-
-static int msm_devfreq_get_cur_freq(struct device *dev, unsigned long *freq)
-{
-	struct msm_gpu *gpu = dev_to_gpu(dev);
-
-	if (gpu->funcs->gpu_get_freq)
-		*freq = gpu->funcs->gpu_get_freq(gpu);
-	else
-		*freq = clk_get_rate(gpu->core_clk);
-
-	return 0;
-}
-
-static struct devfreq_dev_profile msm_devfreq_profile = {
-	.polling_ms = 10,
-	.target = msm_devfreq_target,
-	.get_dev_status = msm_devfreq_get_dev_status,
-	.get_cur_freq = msm_devfreq_get_cur_freq,
-};
-
-static void msm_devfreq_init(struct msm_gpu *gpu)
-{
-	/* We need target support to do devfreq */
-	if (!gpu->funcs->gpu_busy)
-		return;
-
-	msm_devfreq_profile.initial_freq = gpu->fast_rate;
-
-	/*
-	 * Don't set the freq_table or max_state and let devfreq build the table
-	 * from OPP
-	 * After a deferred probe, these may have be left to non-zero values,
-	 * so set them back to zero before creating the devfreq device
-	 */
-	msm_devfreq_profile.freq_table = NULL;
-	msm_devfreq_profile.max_state = 0;
-
-	gpu->devfreq.devfreq = devm_devfreq_add_device(&gpu->pdev->dev,
-			&msm_devfreq_profile, DEVFREQ_GOV_SIMPLE_ONDEMAND,
-			NULL);
-
-	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)
 {
 	struct drm_device *dev = gpu->dev;
@@ -196,14 +94,6 @@ static int disable_axi(struct msm_gpu *gpu)
 	return 0;
 }
 
-void msm_gpu_resume_devfreq(struct msm_gpu *gpu)
-{
-	gpu->devfreq.busy_cycles = 0;
-	gpu->devfreq.time = ktime_get();
-
-	devfreq_resume_device(gpu->devfreq.devfreq);
-}
-
 int msm_gpu_pm_resume(struct msm_gpu *gpu)
 {
 	int ret;
@@ -223,7 +113,7 @@ int msm_gpu_pm_resume(struct msm_gpu *gpu)
 	if (ret)
 		return ret;
 
-	msm_gpu_resume_devfreq(gpu);
+	msm_devfreq_resume(gpu);
 
 	gpu->needs_hw_init = true;
 
@@ -237,7 +127,7 @@ int msm_gpu_pm_suspend(struct msm_gpu *gpu)
 	DBG("%s", gpu->name);
 	trace_msm_gpu_suspend(0);
 
-	devfreq_suspend_device(gpu->devfreq.devfreq);
+	msm_devfreq_suspend(gpu);
 
 	ret = disable_axi(gpu);
 	if (ret)
@@ -1082,5 +972,5 @@ void msm_gpu_cleanup(struct msm_gpu *gpu)
 		kthread_destroy_worker(gpu->worker);
 	}
 
-	devfreq_cooling_unregister(gpu->cooling);
+	msm_devfreq_cleanup(gpu);
 }
diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index 090cb89fa238..ada15e28f251 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -80,6 +80,12 @@ struct msm_gpu_fault_info {
 	const char *block;
 };
 
+struct msm_gpu_devfreq {
+	struct devfreq *devfreq;
+	u64 busy_cycles;
+	ktime_t time;
+};
+
 struct msm_gpu {
 	const char *name;
 	struct drm_device *dev;
@@ -151,11 +157,7 @@ struct msm_gpu {
 
 	struct drm_gem_object *memptrs_bo;
 
-	struct {
-		struct devfreq *devfreq;
-		u64 busy_cycles;
-		ktime_t time;
-	} devfreq;
+	struct msm_gpu_devfreq devfreq;
 
 	uint32_t suspend_count;
 
@@ -377,7 +379,11 @@ static inline void gpu_write64(struct msm_gpu *gpu, u32 lo, u32 hi, u64 val)
 
 int msm_gpu_pm_suspend(struct msm_gpu *gpu);
 int msm_gpu_pm_resume(struct msm_gpu *gpu);
-void msm_gpu_resume_devfreq(struct msm_gpu *gpu);
+
+void msm_devfreq_init(struct msm_gpu *gpu);
+void msm_devfreq_cleanup(struct msm_gpu *gpu);
+void msm_devfreq_resume(struct msm_gpu *gpu);
+void msm_devfreq_suspend(struct msm_gpu *gpu);
 
 int msm_gpu_hw_init(struct msm_gpu *gpu);
 
diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
new file mode 100644
index 000000000000..3bcea0baddab
--- /dev/null
+++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2013 Red Hat
+ * Author: Rob Clark <robdclark@gmail.com>
+ */
+
+#include "msm_gpu.h"
+#include "msm_gpu_trace.h"
+
+#include <linux/devfreq.h>
+#include <linux/devfreq_cooling.h>
+
+/*
+ * Power Management:
+ */
+
+static int msm_devfreq_target(struct device *dev, unsigned long *freq,
+		u32 flags)
+{
+	struct msm_gpu *gpu = dev_to_gpu(dev);
+	struct dev_pm_opp *opp;
+
+	opp = devfreq_recommended_opp(dev, freq, flags);
+
+	if (IS_ERR(opp))
+		return PTR_ERR(opp);
+
+	trace_msm_gpu_freq_change(dev_pm_opp_get_freq(opp));
+
+	if (gpu->funcs->gpu_set_freq)
+		gpu->funcs->gpu_set_freq(gpu, opp);
+	else
+		clk_set_rate(gpu->core_clk, *freq);
+
+	dev_pm_opp_put(opp);
+
+	return 0;
+}
+
+static int msm_devfreq_get_dev_status(struct device *dev,
+		struct devfreq_dev_status *status)
+{
+	struct msm_gpu *gpu = dev_to_gpu(dev);
+	ktime_t time;
+
+	if (gpu->funcs->gpu_get_freq)
+		status->current_frequency = gpu->funcs->gpu_get_freq(gpu);
+	else
+		status->current_frequency = clk_get_rate(gpu->core_clk);
+
+	status->busy_time = gpu->funcs->gpu_busy(gpu);
+
+	time = ktime_get();
+	status->total_time = ktime_us_delta(time, gpu->devfreq.time);
+	gpu->devfreq.time = time;
+
+	return 0;
+}
+
+static int msm_devfreq_get_cur_freq(struct device *dev, unsigned long *freq)
+{
+	struct msm_gpu *gpu = dev_to_gpu(dev);
+
+	if (gpu->funcs->gpu_get_freq)
+		*freq = gpu->funcs->gpu_get_freq(gpu);
+	else
+		*freq = clk_get_rate(gpu->core_clk);
+
+	return 0;
+}
+
+static struct devfreq_dev_profile msm_devfreq_profile = {
+	.polling_ms = 10,
+	.target = msm_devfreq_target,
+	.get_dev_status = msm_devfreq_get_dev_status,
+	.get_cur_freq = msm_devfreq_get_cur_freq,
+};
+
+void msm_devfreq_init(struct msm_gpu *gpu)
+{
+	/* We need target support to do devfreq */
+	if (!gpu->funcs->gpu_busy)
+		return;
+
+	msm_devfreq_profile.initial_freq = gpu->fast_rate;
+
+	/*
+	 * Don't set the freq_table or max_state and let devfreq build the table
+	 * from OPP
+	 * After a deferred probe, these may have be left to non-zero values,
+	 * so set them back to zero before creating the devfreq device
+	 */
+	msm_devfreq_profile.freq_table = NULL;
+	msm_devfreq_profile.max_state = 0;
+
+	gpu->devfreq.devfreq = devm_devfreq_add_device(&gpu->pdev->dev,
+			&msm_devfreq_profile, DEVFREQ_GOV_SIMPLE_ONDEMAND,
+			NULL);
+
+	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;
+	}
+}
+
+void msm_devfreq_cleanup(struct msm_gpu *gpu)
+{
+	devfreq_cooling_unregister(gpu->cooling);
+}
+
+void msm_devfreq_resume(struct msm_gpu *gpu)
+{
+	gpu->devfreq.busy_cycles = 0;
+	gpu->devfreq.time = ktime_get();
+
+	devfreq_resume_device(gpu->devfreq.devfreq);
+}
+
+void msm_devfreq_suspend(struct msm_gpu *gpu)
+{
+	devfreq_suspend_device(gpu->devfreq.devfreq);
+}
-- 
2.31.1

[PATCH 2/3] drm/msm: Split out get_freq() helper

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

In the next patch, it grows a bit more, so lets not duplicate the logic
in multiple places.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/gpu/drm/msm/msm_gpu_devfreq.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
index 3bcea0baddab..2e24a97be624 100644
--- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
+++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
@@ -37,17 +37,21 @@ static int msm_devfreq_target(struct device *dev, unsigned long *freq,
 	return 0;
 }
 
+static unsigned long get_freq(struct msm_gpu *gpu)
+{
+	if (gpu->funcs->gpu_get_freq)
+		return gpu->funcs->gpu_get_freq(gpu);
+
+	return clk_get_rate(gpu->core_clk);
+}
+
 static int msm_devfreq_get_dev_status(struct device *dev,
 		struct devfreq_dev_status *status)
 {
 	struct msm_gpu *gpu = dev_to_gpu(dev);
 	ktime_t time;
 
-	if (gpu->funcs->gpu_get_freq)
-		status->current_frequency = gpu->funcs->gpu_get_freq(gpu);
-	else
-		status->current_frequency = clk_get_rate(gpu->core_clk);
-
+	status->current_frequency = get_freq(gpu);
 	status->busy_time = gpu->funcs->gpu_busy(gpu);
 
 	time = ktime_get();
@@ -59,12 +63,7 @@ static int msm_devfreq_get_dev_status(struct device *dev,
 
 static int msm_devfreq_get_cur_freq(struct device *dev, unsigned long *freq)
 {
-	struct msm_gpu *gpu = dev_to_gpu(dev);
-
-	if (gpu->funcs->gpu_get_freq)
-		*freq = gpu->funcs->gpu_get_freq(gpu);
-	else
-		*freq = clk_get_rate(gpu->core_clk);
+	*freq = get_freq(dev_to_gpu(dev));
 
 	return 0;
 }
-- 
2.31.1

[PATCH 3/3] drm/msm: Devfreq tuning

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

This adds a few things to try and make frequency scaling better match
the workload:

1) Longer polling interval to avoid whip-lashing between too-high and
   too-low frequencies in certain workloads, like mobile games which
   throttle themselves to 30fps.

   Previously our polling interval was short enough to let things
   ramp down to minimum freq in the "off" frame, but long enough to
   not react quickly enough when rendering started on the next frame,
   leading to uneven frame times.  (Ie. rather than a consistent 33ms
   it would alternate between 16/33/48ms.)

2) Awareness of when the GPU is active vs idle.  Since we know when
   the GPU is active vs idle, we can clamp the frequency down to the
   minimum while it is idle.  (If it is idle for long enough, then
   the autosuspend delay will eventually kick in and power down the
   GPU.)

   Since devfreq has no knowledge of powered-but-idle, this takes a
   small bit of trickery to maintain a "fake" frequency while idle.
   This, combined with the longer polling period allows devfreq to
   arrive at a reasonable "active" frequency, while still clamping
   to minimum freq when idle to reduce power draw.

3) Boost.  Because simple_ondemand needs to see a certain threshold
   of busyness to ramp up, we could end up needing multiple polling
   cycles before it reacts appropriately on interactive workloads
   (ex. scrolling a web page after reading for some time), on top
   of the already lengthened polling interval, when we see a idle
   to active transition after a period of idle time we boost the
   frequency that we return to.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/gpu/drm/msm/msm_gpu.c         |  8 +++
 drivers/gpu/drm/msm/msm_gpu.h         |  9 ++++
 drivers/gpu/drm/msm/msm_gpu_devfreq.c | 73 ++++++++++++++++++++++++++-
 3 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
index 70d8610b1b73..68d2df590054 100644
--- a/drivers/gpu/drm/msm/msm_gpu.c
+++ b/drivers/gpu/drm/msm/msm_gpu.c
@@ -667,6 +667,10 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
 	list_del(&submit->node);
 	spin_unlock(&ring->submit_lock);
 
+	/* Update devfreq on transition from active->idle: */
+	if (atomic_dec_return(&gpu->active_submits) == 0)
+		msm_devfreq_idle(gpu);
+
 	msm_gem_submit_put(submit);
 }
 
@@ -747,6 +751,10 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
 	list_add_tail(&submit->node, &ring->submits);
 	spin_unlock(&ring->submit_lock);
 
+	/* Update devfreq on transition from idle->active: */
+	if (atomic_inc_return(&gpu->active_submits) == 1)
+		msm_devfreq_active(gpu);
+
 	gpu->funcs->submit(gpu, submit);
 	priv->lastctx = submit->queue->ctx;
 
diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index ada15e28f251..e14edda3d778 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -84,6 +84,10 @@ struct msm_gpu_devfreq {
 	struct devfreq *devfreq;
 	u64 busy_cycles;
 	ktime_t time;
+
+	/* Time and freq of last transition to idle: */
+	ktime_t idle_time;
+	unsigned long idle_freq;
 };
 
 struct msm_gpu {
@@ -115,6 +119,9 @@ struct msm_gpu {
 	 */
 	struct list_head active_list;
 
+	/* number of in-flight submits: */
+	atomic_t active_submits;
+
 	/* does gpu need hw_init? */
 	bool needs_hw_init;
 
@@ -384,6 +391,8 @@ void msm_devfreq_init(struct msm_gpu *gpu);
 void msm_devfreq_cleanup(struct msm_gpu *gpu);
 void msm_devfreq_resume(struct msm_gpu *gpu);
 void msm_devfreq_suspend(struct msm_gpu *gpu);
+void msm_devfreq_active(struct msm_gpu *gpu);
+void msm_devfreq_idle(struct msm_gpu *gpu);
 
 int msm_gpu_hw_init(struct msm_gpu *gpu);
 
diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
index 2e24a97be624..0a1ee20296a2 100644
--- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
+++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
@@ -22,6 +22,15 @@ static int msm_devfreq_target(struct device *dev, unsigned long *freq,
 
 	opp = devfreq_recommended_opp(dev, freq, flags);
 
+	/*
+	 * If the GPU is idle, devfreq is not aware, so just ignore
+	 * it's requests
+	 */
+	if (gpu->devfreq.idle_freq) {
+		gpu->devfreq.idle_freq = *freq;
+		return 0;
+	}
+
 	if (IS_ERR(opp))
 		return PTR_ERR(opp);
 
@@ -39,6 +48,9 @@ static int msm_devfreq_target(struct device *dev, unsigned long *freq,
 
 static unsigned long get_freq(struct msm_gpu *gpu)
 {
+	if (gpu->devfreq.idle_freq)
+		return gpu->devfreq.idle_freq;
+
 	if (gpu->funcs->gpu_get_freq)
 		return gpu->funcs->gpu_get_freq(gpu);
 
@@ -69,7 +81,8 @@ static int msm_devfreq_get_cur_freq(struct device *dev, unsigned long *freq)
 }
 
 static struct devfreq_dev_profile msm_devfreq_profile = {
-	.polling_ms = 10,
+	.timer = DEVFREQ_TIMER_DELAYED,
+	.polling_ms = 50,
 	.target = msm_devfreq_target,
 	.get_dev_status = msm_devfreq_get_dev_status,
 	.get_cur_freq = msm_devfreq_get_cur_freq,
@@ -130,3 +143,61 @@ void msm_devfreq_suspend(struct msm_gpu *gpu)
 {
 	devfreq_suspend_device(gpu->devfreq.devfreq);
 }
+
+void msm_devfreq_active(struct msm_gpu *gpu)
+{
+	struct msm_gpu_devfreq *df = &gpu->devfreq;
+	struct devfreq_dev_status status;
+	unsigned int idle_time;
+	unsigned long target_freq = df->idle_freq;
+
+	/*
+	 * Hold devfreq lock to synchronize with get_dev_status()/
+	 * target() callbacks
+	 */
+	mutex_lock(&df->devfreq->lock);
+
+	idle_time = ktime_to_ms(ktime_sub(ktime_get(), df->idle_time));
+
+	/*
+	 * If we've been idle for a significant fraction of a polling
+	 * interval, then we won't meet the threshold of busyness for
+	 * the governor to ramp up the freq.. so give some boost
+	 */
+	if (idle_time > msm_devfreq_profile.polling_ms/2) {
+		target_freq *= 2;
+	}
+
+	df->idle_freq = 0;
+
+	msm_devfreq_target(&gpu->pdev->dev, &target_freq, 0);
+
+	/*
+	 * Reset the polling interval so we aren't inconsistent
+	 * about freq vs busy/total cycles
+	 */
+	msm_devfreq_get_dev_status(&gpu->pdev->dev, &status);
+
+	mutex_unlock(&df->devfreq->lock);
+}
+
+void msm_devfreq_idle(struct msm_gpu *gpu)
+{
+	struct msm_gpu_devfreq *df = &gpu->devfreq;
+	unsigned long idle_freq, target_freq = 0;
+
+	/*
+	 * Hold devfreq lock to synchronize with get_dev_status()/
+	 * target() callbacks
+	 */
+	mutex_lock(&df->devfreq->lock);
+
+	idle_freq = get_freq(gpu);
+
+	msm_devfreq_target(&gpu->pdev->dev, &target_freq, 0);
+
+	df->idle_time = ktime_get();
+	df->idle_freq = idle_freq;
+
+	mutex_unlock(&df->devfreq->lock);
+}
-- 
2.31.1

Re: [PATCH 3/3] drm/msm: Devfreq tuning

[Akhil P Oommen]

On 7/23/2021 3:51 AM, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> This adds a few things to try and make frequency scaling better match
> the workload:
> 
> 1) Longer polling interval to avoid whip-lashing between too-high and
>     too-low frequencies in certain workloads, like mobile games which
>     throttle themselves to 30fps.
> 
>     Previously our polling interval was short enough to let things
>     ramp down to minimum freq in the "off" frame, but long enough to
>     not react quickly enough when rendering started on the next frame,
>     leading to uneven frame times.  (Ie. rather than a consistent 33ms
>     it would alternate between 16/33/48ms.)
> 
> 2) Awareness of when the GPU is active vs idle.  Since we know when
>     the GPU is active vs idle, we can clamp the frequency down to the
>     minimum while it is idle.  (If it is idle for long enough, then
>     the autosuspend delay will eventually kick in and power down the
>     GPU.)
> 
>     Since devfreq has no knowledge of powered-but-idle, this takes a
>     small bit of trickery to maintain a "fake" frequency while idle.
>     This, combined with the longer polling period allows devfreq to
>     arrive at a reasonable "active" frequency, while still clamping
>     to minimum freq when idle to reduce power draw.
> 
> 3) Boost.  Because simple_ondemand needs to see a certain threshold
>     of busyness to ramp up, we could end up needing multiple polling
>     cycles before it reacts appropriately on interactive workloads
>     (ex. scrolling a web page after reading for some time), on top
>     of the already lengthened polling interval, when we see a idle
>     to active transition after a period of idle time we boost the
>     frequency that we return to.
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
>   drivers/gpu/drm/msm/msm_gpu.c         |  8 +++
>   drivers/gpu/drm/msm/msm_gpu.h         |  9 ++++
>   drivers/gpu/drm/msm/msm_gpu_devfreq.c | 73 ++++++++++++++++++++++++++-
>   3 files changed, 89 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> index 70d8610b1b73..68d2df590054 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.c
> +++ b/drivers/gpu/drm/msm/msm_gpu.c
> @@ -667,6 +667,10 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
>   	list_del(&submit->node);
>   	spin_unlock(&ring->submit_lock);
>   
> +	/* Update devfreq on transition from active->idle: */
> +	if (atomic_dec_return(&gpu->active_submits) == 0)
This will race with the submit path. To avoid that, this test and the 
msm_devfreq_idle should be under the same lock. Same applies for the 
submit path.

-Akhil
> +		msm_devfreq_idle(gpu);
> +
>   	msm_gem_submit_put(submit);
>   }
>   
> @@ -747,6 +751,10 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>   	list_add_tail(&submit->node, &ring->submits);
>   	spin_unlock(&ring->submit_lock);
>   
> +	/* Update devfreq on transition from idle->active: */
> +	if (atomic_inc_return(&gpu->active_submits) == 1)
> +		msm_devfreq_active(gpu);
> +
>   	gpu->funcs->submit(gpu, submit);
>   	priv->lastctx = submit->queue->ctx;
>   
> diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
> index ada15e28f251..e14edda3d778 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.h
> +++ b/drivers/gpu/drm/msm/msm_gpu.h
> @@ -84,6 +84,10 @@ struct msm_gpu_devfreq {
>   	struct devfreq *devfreq;
>   	u64 busy_cycles;
>   	ktime_t time;
> +
> +	/* Time and freq of last transition to idle: */
> +	ktime_t idle_time;
> +	unsigned long idle_freq;
>   };
>   
>   struct msm_gpu {
> @@ -115,6 +119,9 @@ struct msm_gpu {
>   	 */
>   	struct list_head active_list;
>   
> +	/* number of in-flight submits: */
> +	atomic_t active_submits;
> +
>   	/* does gpu need hw_init? */
>   	bool needs_hw_init;
>   
> @@ -384,6 +391,8 @@ void msm_devfreq_init(struct msm_gpu *gpu);
>   void msm_devfreq_cleanup(struct msm_gpu *gpu);
>   void msm_devfreq_resume(struct msm_gpu *gpu);
>   void msm_devfreq_suspend(struct msm_gpu *gpu);
> +void msm_devfreq_active(struct msm_gpu *gpu);
> +void msm_devfreq_idle(struct msm_gpu *gpu);
>   
>   int msm_gpu_hw_init(struct msm_gpu *gpu);
>   
> diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> index 2e24a97be624..0a1ee20296a2 100644
> --- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> +++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> @@ -22,6 +22,15 @@ static int msm_devfreq_target(struct device *dev, unsigned long *freq,
>   
>   	opp = devfreq_recommended_opp(dev, freq, flags);
>   
> +	/*
> +	 * If the GPU is idle, devfreq is not aware, so just ignore
> +	 * it's requests
> +	 */
> +	if (gpu->devfreq.idle_freq) {
> +		gpu->devfreq.idle_freq = *freq;
> +		return 0;
> +	}
> +
>   	if (IS_ERR(opp))
>   		return PTR_ERR(opp);
>   
> @@ -39,6 +48,9 @@ static int msm_devfreq_target(struct device *dev, unsigned long *freq,
>   
>   static unsigned long get_freq(struct msm_gpu *gpu)
>   {
> +	if (gpu->devfreq.idle_freq)
> +		return gpu->devfreq.idle_freq;
> +
>   	if (gpu->funcs->gpu_get_freq)
>   		return gpu->funcs->gpu_get_freq(gpu);
>   
> @@ -69,7 +81,8 @@ static int msm_devfreq_get_cur_freq(struct device *dev, unsigned long *freq)
>   }
>   
>   static struct devfreq_dev_profile msm_devfreq_profile = {
> -	.polling_ms = 10,
> +	.timer = DEVFREQ_TIMER_DELAYED,
> +	.polling_ms = 50,
>   	.target = msm_devfreq_target,
>   	.get_dev_status = msm_devfreq_get_dev_status,
>   	.get_cur_freq = msm_devfreq_get_cur_freq,
> @@ -130,3 +143,61 @@ void msm_devfreq_suspend(struct msm_gpu *gpu)
>   {
>   	devfreq_suspend_device(gpu->devfreq.devfreq);
>   }
> +
> +void msm_devfreq_active(struct msm_gpu *gpu)
> +{
> +	struct msm_gpu_devfreq *df = &gpu->devfreq;
> +	struct devfreq_dev_status status;
> +	unsigned int idle_time;
> +	unsigned long target_freq = df->idle_freq;
> +
> +	/*
> +	 * Hold devfreq lock to synchronize with get_dev_status()/
> +	 * target() callbacks
> +	 */
> +	mutex_lock(&df->devfreq->lock);
> +
> +	idle_time = ktime_to_ms(ktime_sub(ktime_get(), df->idle_time));
> +
> +	/*
> +	 * If we've been idle for a significant fraction of a polling
> +	 * interval, then we won't meet the threshold of busyness for
> +	 * the governor to ramp up the freq.. so give some boost
> +	 */
> +	if (idle_time > msm_devfreq_profile.polling_ms/2) {
> +		target_freq *= 2;
> +	}
> +
> +	df->idle_freq = 0;
> +
> +	msm_devfreq_target(&gpu->pdev->dev, &target_freq, 0);
> +
> +	/*
> +	 * Reset the polling interval so we aren't inconsistent
> +	 * about freq vs busy/total cycles
> +	 */
> +	msm_devfreq_get_dev_status(&gpu->pdev->dev, &status);
> +
> +	mutex_unlock(&df->devfreq->lock);
> +}
> +
> +void msm_devfreq_idle(struct msm_gpu *gpu)
> +{
> +	struct msm_gpu_devfreq *df = &gpu->devfreq;
> +	unsigned long idle_freq, target_freq = 0;
> +
> +	/*
> +	 * Hold devfreq lock to synchronize with get_dev_status()/
> +	 * target() callbacks
> +	 */
> +	mutex_lock(&df->devfreq->lock);
> +
> +	idle_freq = get_freq(gpu);
> +
> +	msm_devfreq_target(&gpu->pdev->dev, &target_freq, 0);
> +
> +	df->idle_time = ktime_get();
> +	df->idle_freq = idle_freq;
> +
> +	mutex_unlock(&df->devfreq->lock);
> +}
>