[PATCH v2 3/3] drm/msm/gpu: Respect PM QoS constraints

Rob Clark
2021-11-24T21:37:53Z

Re-work the boost and idle clamping to use PM QoS requests instead, so
they get aggreggated with other requests (such as cooling device).

This does have the minor side-effect that devfreq sysfs min_freq/
max_freq files now reflect the boost and idle clamping, as they show
(despite what they are documented to show) the aggregated min/max freq.
Fixing that in devfreq does not look straightforward after considering
that OPPs can be dynamically added/removed. However writes to the
sysfs files still behave as expected.

v2: Use 64b math to avoid potential 32b overflow

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
drivers/gpu/drm/msm/msm_gpu.h | 33 +++++++---
drivers/gpu/drm/msm/msm_gpu_devfreq.c | 87 +++++++++++++++------------
2 files changed, 71 insertions(+), 49 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index 59cdd00b69d0..96d8d37dd5b7 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -87,6 +87,21 @@ struct msm_gpu_devfreq {
/** devfreq: devfreq instance */
struct devfreq *devfreq;

+ /**
+ * idle_constraint:
+ *
+ * A PM QoS constraint to limit max freq while the GPU is idle.
+ */
+ struct dev_pm_qos_request idle_freq;
+
+ /**
+ * boost_constraint:
+ *
+ * A PM QoS constraint to boost min freq for a period of time
+ * until the boost expires.
+ */
+ struct dev_pm_qos_request boost_freq;
+
/**
* busy_cycles:
*
@@ -103,22 +118,19 @@ struct msm_gpu_devfreq {
ktime_t idle_time;

/**
- * idle_freq:
+ * idle_work:
*
- * Shadow frequency used while the GPU is idle. From the PoV of
- * the devfreq governor, we are continuing to sample busyness and
- * adjust frequency while the GPU is idle, but we use this shadow
- * value as the GPU is actually clamped to minimum frequency while
- * it is inactive.
+ * Used to delay clamping to idle freq on active->idle transition.
*/
- unsigned long idle_freq;
+ struct msm_hrtimer_work idle_work;

/**
- * idle_work:
+ * boost_work:
*
- * Used to delay clamping to idle freq on active->idle transition.
+ * Used to reset the boost_constraint after the boost period has
+ * elapsed
*/
- struct msm_hrtimer_work idle_work;
+ struct msm_hrtimer_work boost_work;
};

struct msm_gpu {
@@ -498,6 +510,7 @@ 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_boost(struct msm_gpu *gpu, unsigned factor);
void msm_devfreq_active(struct msm_gpu *gpu);
void msm_devfreq_idle(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 1f55242bb6a1..11be623de2ab 100644
--- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
+++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
@@ -9,6 +9,7 @@

#include <linux/devfreq.h>
#include <linux/devfreq_cooling.h>
+#include <linux/units.h>

/*
* Power Management:
@@ -22,15 +23,6 @@ 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);

@@ -48,9 +40,6 @@ 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);

@@ -88,6 +77,7 @@ static struct devfreq_dev_profile msm_devfreq_profile = {
.get_cur_freq = msm_devfreq_get_cur_freq,
};

+static void msm_devfreq_boost_work(struct kthread_work *work);
static void msm_devfreq_idle_work(struct kthread_work *work);

void msm_devfreq_init(struct msm_gpu *gpu)
@@ -98,6 +88,12 @@ void msm_devfreq_init(struct msm_gpu *gpu)
if (!gpu->funcs->gpu_busy)
return;

+ dev_pm_qos_add_request(&gpu->pdev->dev, &df->idle_freq,
+ DEV_PM_QOS_MAX_FREQUENCY,
+ PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE);
+ dev_pm_qos_add_request(&gpu->pdev->dev, &df->boost_freq,
+ DEV_PM_QOS_MIN_FREQUENCY, 0);
+
msm_devfreq_profile.initial_freq = gpu->fast_rate;

/*
@@ -128,13 +124,19 @@ void msm_devfreq_init(struct msm_gpu *gpu)
gpu->cooling = NULL;
}

+ msm_hrtimer_work_init(&df->boost_work, gpu->worker, msm_devfreq_boost_work,
+ CLOCK_MONOTONIC, HRTIMER_MODE_REL);
msm_hrtimer_work_init(&df->idle_work, gpu->worker, msm_devfreq_idle_work,
CLOCK_MONOTONIC, HRTIMER_MODE_REL);
}

void msm_devfreq_cleanup(struct msm_gpu *gpu)
{
+ struct msm_gpu_devfreq *df = &gpu->devfreq;
+
devfreq_cooling_unregister(gpu->cooling);
+ dev_pm_qos_remove_request(&df->boost_freq);
+ dev_pm_qos_remove_request(&df->idle_freq);
}

void msm_devfreq_resume(struct msm_gpu *gpu)
@@ -150,12 +152,40 @@ void msm_devfreq_suspend(struct msm_gpu *gpu)
devfreq_suspend_device(gpu->devfreq.devfreq);
}

+static void msm_devfreq_boost_work(struct kthread_work *work)
+{
+ struct msm_gpu_devfreq *df = container_of(work,
+ struct msm_gpu_devfreq, boost_work.work);
+
+ dev_pm_qos_update_request(&df->boost_freq, 0);
+}
+
+void msm_devfreq_boost(struct msm_gpu *gpu, unsigned factor)
+{
+ struct msm_gpu_devfreq *df = &gpu->devfreq;
+ uint64_t freq;
+
+ freq = get_freq(gpu);
+ freq *= factor;
+
+ /*
+ * A nice little trap is that PM QoS operates in terms of KHz,
+ * while devfreq operates in terms of Hz:
+ */
+ do_div(freq, HZ_PER_KHZ);
+
+ dev_pm_qos_update_request(&df->boost_freq, freq);
+
+ msm_hrtimer_queue_work(&df->boost_work,
+ ms_to_ktime(msm_devfreq_profile.polling_ms),
+ HRTIMER_MODE_REL);
+}
+
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;

if (!df->devfreq)
return;
@@ -165,12 +195,6 @@ void msm_devfreq_active(struct msm_gpu *gpu)
*/
hrtimer_cancel(&df->idle_work.timer);

- /*
- * 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));

/*
@@ -179,20 +203,17 @@ void msm_devfreq_active(struct msm_gpu *gpu)
* the governor to ramp up the freq.. so give some boost
*/
if (idle_time > msm_devfreq_profile.polling_ms) {
- target_freq *= 2;
+ msm_devfreq_boost(gpu, 2);
}

- df->idle_freq = 0;
-
- msm_devfreq_target(&gpu->pdev->dev, &target_freq, 0);
+ dev_pm_qos_update_request(&df->idle_freq,
+ PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE);

/*
* 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);
}

@@ -201,23 +222,11 @@ static void msm_devfreq_idle_work(struct kthread_work *work)
struct msm_gpu_devfreq *df = container_of(work,
struct msm_gpu_devfreq, idle_work.work);
struct msm_gpu *gpu = container_of(df, struct msm_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);
-
- if (gpu->clamp_to_idle)
- msm_devfreq_target(&gpu->pdev->dev, &target_freq, 0);

df->idle_time = ktime_get();
- df->idle_freq = idle_freq;

- mutex_unlock(&df->devfreq->lock);
+ if (gpu->clamp_to_idle)
+ dev_pm_qos_update_request(&df->idle_freq, 0);
}

void msm_devfreq_idle(struct msm_gpu *gpu)
--
2.33.1