On Fri, Apr 15, 2022 at 5:33 PM Chia-I Wu olvaffe@gmail.com wrote:
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.
The idea is to extend devfreq_simple_ondemand_data to specify whether devfreq_simple_ondemand_func should use "last status" or "average status" to determine the target frequency. devfreq core will need to store "struct devfreq_dev_status average_status", which will be updated when a device uses simple_ondemand and asks for average_status instead of last_status.
Fixes: 7c0ffcd40b16 ("drm/msm/gpu: Respect PM QoS constraints") Signed-off-by: Chia-I Wu olvaffe@gmail.com Cc: Rob Clark robdclark@chromium.org
drivers/gpu/drm/msm/msm_gpu.h | 3 ++ drivers/gpu/drm/msm/msm_gpu_devfreq.c | 60 ++++++++++++++++++++++++++- 2 files changed, 62 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h index 389c6dab751b..143c56f5185b 100644 --- a/drivers/gpu/drm/msm/msm_gpu.h +++ b/drivers/gpu/drm/msm/msm_gpu.h @@ -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> @@ -117,6 +118,8 @@ struct msm_gpu_devfreq { /** idle_time: Time of last transition to idle: */ ktime_t idle_time;
struct devfreq_dev_status average_status;/** * idle_work: *diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c index f531015107c3..d2539ca78c29 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/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;}
2.36.0.rc0.470.gd361397f0d-goog