On 25/11/2023 20:52, Adrián Larumbe wrote:
> It was noticed when setting the Panfrost's DVFS device to the performant
> governor, GPU frequency as reported by fdinfo had dropped to 0 permamently.
>
> There are two separate issues causing this behaviour:
> - Not initialising the device's current_frequency variable to its original
> value during device probe().
> - Updating said variable in Panfrost devfreq's get_dev_status() rather
> than after the new OPP's frequency had been retrieved in target(), which
> meant the old frequency would be assigned instead.
Good catch - I'd not looked at the performance governor. I'd assumed
that one was "too simple to be wrong" ;)
Reviewed-by: Steven Price <steven.price@xxxxxxx>
>
> Signed-off-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
> Fixes: f11b0417eec2 ("drm/panfrost: Add fdinfo support GPU load metrics")
> ---
> drivers/gpu/drm/panfrost/panfrost_devfreq.c | 17 +++++++++++++++--
> 1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> index f59c82ea8870..2d30da38c2c3 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> @@ -29,14 +29,20 @@ static void panfrost_devfreq_update_utilization(struct panfrost_devfreq *pfdevfr
> static int panfrost_devfreq_target(struct device *dev, unsigned long *freq,
> u32 flags)
> {
> + struct panfrost_device *ptdev = dev_get_drvdata(dev);
> struct dev_pm_opp *opp;
> + int err;
>
> opp = devfreq_recommended_opp(dev, freq, flags);
> if (IS_ERR(opp))
> return PTR_ERR(opp);
> dev_pm_opp_put(opp);
>
> - return dev_pm_opp_set_rate(dev, *freq);
> + err = dev_pm_opp_set_rate(dev, *freq);
> + if (!err)
> + ptdev->pfdevfreq.current_frequency = *freq;
> +
> + return err;
> }
>
> static void panfrost_devfreq_reset(struct panfrost_devfreq *pfdevfreq)
> @@ -58,7 +64,6 @@ static int panfrost_devfreq_get_dev_status(struct device *dev,
> spin_lock_irqsave(&pfdevfreq->lock, irqflags);
>
> panfrost_devfreq_update_utilization(pfdevfreq);
> - pfdevfreq->current_frequency = status->current_frequency;
>
> status->total_time = ktime_to_ns(ktime_add(pfdevfreq->busy_time,
> pfdevfreq->idle_time));
> @@ -164,6 +169,14 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>
> panfrost_devfreq_profile.initial_freq = cur_freq;
>
> + /*
> + * We could wait until panfrost_devfreq_target() to set this value, but
> + * since the simple_ondemand governor works asynchronously, there's a
> + * chance by the time someone opens the device's fdinfo file, current
> + * frequency hasn't been updated yet, so let's just do an early set.
> + */
> + pfdevfreq->current_frequency = cur_freq;
> +
> /*
> * Set the recommend OPP this will enable and configure the regulator
> * if any and will avoid a switch off by regulator_late_cleanup()
