[PATCH 6.1 168/772] drm/msm/gpu: Bypass PM QoS constraint for idle clamp

6.1-stable review patch. If anyone has any objections, please let me know.

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From: Rob Clark robdclark@chromium.org

[ Upstream commit fadcc3ab1302d4e5baa32c272b658221f0066696 ]

Change idle freq clamping back to the direct method, bypassing PM QoS requests. The problem with using PM QoS requests is they call (indirectly) the governors ->get_target_freq() which goes thru a get_dev_status() cycle. The problem comes when the GPU becomes active again and we remove the idle-clamp request, we go through another get_dev_status() cycle for the period that the GPU has been idle, which triggers the governor to lower the target freq excessively.

This partially reverts commit 7c0ffcd40b16 ("drm/msm/gpu: Respect PM QoS constraints"), but preserves the use of boost QoS request, so that it will continue to play nicely with other QoS requests such as a cooling device. This also mostly undoes commit 78f815c1cf8f ("drm/msm: return the average load over the polling period")

Signed-off-by: Rob Clark robdclark@chromium.org Patchwork: https://patchwork.freedesktop.org/patch/517785/ Link: https://lore.kernel.org/r/20230110231447.1939101-3-robdclark@gmail.com Reviewed-by: Chia-I Wu olvaffe@gmail.com Stable-dep-of: 8f32ddd87e49 ("drm/msm/gpu: Check the status of registration to PM QoS") Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/msm/msm_gpu.h | 12 ++- drivers/gpu/drm/msm/msm_gpu_devfreq.c | 135 +++++++++++--------------- 2 files changed, 65 insertions(+), 82 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h index a326b6d1adbe2..5929ecaa1fcdc 100644 --- a/drivers/gpu/drm/msm/msm_gpu.h +++ b/drivers/gpu/drm/msm/msm_gpu.h @@ -109,11 +109,15 @@ struct msm_gpu_devfreq { struct mutex lock;

/** - * idle_constraint: + * idle_freq: * - * A PM QoS constraint to limit max freq while the GPU is idle. + * 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. */ - struct dev_pm_qos_request idle_freq; + unsigned long idle_freq;

/** * boost_constraint: @@ -135,8 +139,6 @@ struct msm_gpu_devfreq { /** idle_time: Time of last transition to idle: */ ktime_t idle_time;

- struct devfreq_dev_status average_status; - /** * idle_work: * diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c index 1f4e2dd8e76dd..ae5380e2abf76 100644 --- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c +++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c @@ -33,6 +33,16 @@ static int msm_devfreq_target(struct device *dev, unsigned long *freq,

trace_msm_gpu_freq_change(dev_pm_opp_get_freq(opp));

+ /* + * If the GPU is idle, devfreq is not aware, so just stash + * the new target freq (to use when we return to active) + */ + if (df->idle_freq) { + df->idle_freq = *freq; + dev_pm_opp_put(opp); + return 0; + } + if (gpu->funcs->gpu_set_freq) { mutex_lock(&df->lock); gpu->funcs->gpu_set_freq(gpu, opp, df->suspended); @@ -48,15 +58,26 @@ static int msm_devfreq_target(struct device *dev, unsigned long *freq,

static unsigned long get_freq(struct msm_gpu *gpu) { + struct msm_gpu_devfreq *df = &gpu->devfreq; + + /* + * If the GPU is idle, use the shadow/saved freq to avoid + * confusing devfreq (which is unaware that we are switching + * to lowest freq until the device is active again) + */ + if (df->idle_freq) + return df->idle_freq; + if (gpu->funcs->gpu_get_freq) return gpu->funcs->gpu_get_freq(gpu);

return clk_get_rate(gpu->core_clk); }

-static void get_raw_dev_status(struct msm_gpu *gpu, +static int msm_devfreq_get_dev_status(struct device *dev, struct devfreq_dev_status *status) { + struct msm_gpu *gpu = dev_to_gpu(dev); struct msm_gpu_devfreq *df = &gpu->devfreq; u64 busy_cycles, busy_time; unsigned long sample_rate; @@ -72,7 +93,7 @@ static void get_raw_dev_status(struct msm_gpu *gpu, if (df->suspended) { mutex_unlock(&df->lock); status->busy_time = 0; - return; + return 0; }

busy_cycles = gpu->funcs->gpu_busy(gpu, &sample_rate); @@ -87,71 +108,6 @@ static void get_raw_dev_status(struct msm_gpu *gpu, busy_time = ~0LU;

status->busy_time = busy_time; -} - -static void update_average_dev_status(struct msm_gpu *gpu, - const struct devfreq_dev_status *raw) -{ - struct msm_gpu_devfreq *df = &gpu->devfreq; - const u32 polling_ms = df->devfreq->profile->polling_ms; - const u32 max_history_ms = polling_ms * 11 / 10; - struct devfreq_dev_status *avg = &df->average_status; - u64 avg_freq; - - /* simple_ondemand governor interacts poorly with gpu->clamp_to_idle. - * When we enforce the constraint on idle, it calls get_dev_status - * which would normally reset the stats. When we remove the - * constraint on active, it calls get_dev_status again where busy_time - * would be 0. - * - * To remedy this, we always return the average load over the past - * polling_ms. - */ - - /* raw is longer than polling_ms or avg has no history */ - if (div_u64(raw->total_time, USEC_PER_MSEC) >= polling_ms || - !avg->total_time) { - *avg = *raw; - return; - } - - /* Truncate the oldest history first. - * - * Because we keep the history with a single devfreq_dev_status, - * rather than a list of devfreq_dev_status, we have to assume freq - * and load are the same over avg->total_time. We can scale down - * avg->busy_time and avg->total_time by the same factor to drop - * history. - */ - if (div_u64(avg->total_time + raw->total_time, USEC_PER_MSEC) >= - max_history_ms) { - const u32 new_total_time = polling_ms * USEC_PER_MSEC - - raw->total_time; - avg->busy_time = div_u64( - mul_u32_u32(avg->busy_time, new_total_time), - avg->total_time); - avg->total_time = new_total_time; - } - - /* compute the average freq over avg->total_time + raw->total_time */ - avg_freq = mul_u32_u32(avg->current_frequency, avg->total_time); - avg_freq += mul_u32_u32(raw->current_frequency, raw->total_time); - do_div(avg_freq, avg->total_time + raw->total_time); - - avg->current_frequency = avg_freq; - avg->busy_time += raw->busy_time; - avg->total_time += raw->total_time; -} - -static int msm_devfreq_get_dev_status(struct device *dev, - struct devfreq_dev_status *status) -{ - struct msm_gpu *gpu = dev_to_gpu(dev); - struct devfreq_dev_status raw; - - get_raw_dev_status(gpu, &raw); - update_average_dev_status(gpu, &raw); - *status = gpu->devfreq.average_status;

return 0; } @@ -191,9 +147,6 @@ void msm_devfreq_init(struct msm_gpu *gpu)

mutex_init(&df->lock);

- 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);

@@ -214,7 +167,6 @@ void msm_devfreq_init(struct msm_gpu *gpu)

if (IS_ERR(df->devfreq)) { DRM_DEV_ERROR(&gpu->pdev->dev, "Couldn't initialize GPU devfreq\n"); - dev_pm_qos_remove_request(&df->idle_freq); dev_pm_qos_remove_request(&df->boost_freq); df->devfreq = NULL; return; @@ -256,7 +208,6 @@ void msm_devfreq_cleanup(struct msm_gpu *gpu)

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) @@ -329,6 +280,7 @@ void msm_devfreq_active(struct msm_gpu *gpu) { struct msm_gpu_devfreq *df = &gpu->devfreq; unsigned int idle_time; + unsigned long target_freq;

if (!has_devfreq(gpu)) return; @@ -338,8 +290,28 @@ void msm_devfreq_active(struct msm_gpu *gpu) */ cancel_idle_work(df);

+ /* + * Hold devfreq lock to synchronize with get_dev_status()/ + * target() callbacks + */ + mutex_lock(&df->devfreq->lock); + + target_freq = df->idle_freq; + idle_time = ktime_to_ms(ktime_sub(ktime_get(), df->idle_time));

+ df->idle_freq = 0; + + /* + * We could have become active again before the idle work had a + * chance to run, in which case the df->idle_freq would have + * still been zero. In this case, no need to change freq. + */ + if (target_freq) + msm_devfreq_target(&gpu->pdev->dev, &target_freq, 0); + + mutex_unlock(&df->devfreq->lock); + /* * If we've been idle for a significant fraction of a polling * interval, then we won't meet the threshold of busyness for @@ -348,9 +320,6 @@ void msm_devfreq_active(struct msm_gpu *gpu) if (idle_time > msm_devfreq_profile.polling_ms) { msm_devfreq_boost(gpu, 2); } - - dev_pm_qos_update_request(&df->idle_freq, - PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE); }

@@ -360,11 +329,23 @@ static void msm_devfreq_idle_work(struct kthread_work *work) struct msm_gpu_devfreq, idle_work.work); struct msm_gpu *gpu = container_of(df, struct msm_gpu, devfreq); struct msm_drm_private *priv = gpu->dev->dev_private; + unsigned long idle_freq, target_freq = 0;

- df->idle_time = ktime_get(); + /* + * Hold devfreq lock to synchronize with get_dev_status()/ + * target() callbacks + */ + mutex_lock(&df->devfreq->lock); + + idle_freq = get_freq(gpu);

if (priv->gpu_clamp_to_idle) - dev_pm_qos_update_request(&df->idle_freq, 0); + msm_devfreq_target(&gpu->pdev->dev, &target_freq, 0); + + df->idle_time = ktime_get(); + df->idle_freq = idle_freq; + + mutex_unlock(&df->devfreq->lock); }

void msm_devfreq_idle(struct msm_gpu *gpu)