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drm/msm: return the average load over the polling period

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simple_ondemand interacts poorly with clamp_to_idle.  It only looks at
the load since the last get_dev_status call, while it should really look
at the load over polling_ms.  When clamp_to_idle true, it almost always
picks the lowest frequency on active because the gpu is idle between
msm_devfreq_idle/msm_devfreq_active.

This logic could potentially be moved into devfreq core.

Fixes: 7c0ffcd40b ("drm/msm/gpu: Respect PM QoS constraints")
Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Cc: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20220416003314.59211-3-olvaffe@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>
This commit is contained in:
Chia-I Wu 2022-04-15 17:33:14 -07:00 • committed by Rob Clark
parent 15c411980b
commit 78f815c1cf
2 changed files with 62 additions and 1 deletions
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3
drivers/gpu/drm/msm/msm_gpu.h
View file

@ -9,6 +9,7 @@
#include <linux/adreno-smmu-priv.h>
#include <linux/clk.h>
#include <linux/devfreq.h>
#include <linux/interconnect.h>
#include <linux/pm_opp.h>
#include <linux/regulator/consumer.h>
@ -118,6 +119,8 @@ struct msm_gpu_devfreq {
/** idle_time: Time of last transition to idle: */
ktime_t idle_time;
struct devfreq_dev_status average_status;
/**
* idle_work:
*

60
drivers/gpu/drm/msm/msm_gpu_devfreq.c
View file

@ -9,6 +9,7 @@
#include <linux/devfreq.h>
#include <linux/devfreq_cooling.h>
#include <linux/math64.h>
#include <linux/units.h>
/*
@ -75,12 +76,69 @@ static void get_raw_dev_status(struct msm_gpu *gpu,
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, status);
get_raw_dev_status(gpu, &raw);
update_average_dev_status(gpu, &raw);
*status = gpu->devfreq.average_status;
return 0;
}