From: Ionela Voinescu <ionela.voinescu@arm.com>
To: Lukasz Luba <lukasz.luba@arm.com>
Cc: amit.kucheria@verdurent.com, linux-pm@vger.kernel.org,
airlied@linux.ie, daniel.lezcano@linaro.org,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
steven.price@arm.com, alyssa.rosenzweig@collabora.com,
rui.zhang@intel.com, orjan.eide@arm.com
Subject: Re: [PATCH 2/5] thermal: devfreq_cooling: get a copy of device status
Date: Wed, 7 Oct 2020 17:11:20 +0100 [thread overview]
Message-ID: <20201007161120.GC15063@arm.com> (raw)
In-Reply-To: <20200921122007.29610-3-lukasz.luba@arm.com>
On Monday 21 Sep 2020 at 13:20:04 (+0100), Lukasz Luba wrote:
> Devfreq cooling needs to now the correct status of the device in order
> to operate. Do not rely on Devfreq last_status which might be a stale data
> and get more up-to-date values of the load.
>
> Devfreq framework can change the device status in the background. To
> mitigate this situation make a copy of the status structure and use it
> for internal calculations.
>
> In addition this patch adds normalization function, which also makes sure
> that whatever data comes from the device, it is in a sane range.
>
> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
> ---
> drivers/thermal/devfreq_cooling.c | 52 +++++++++++++++++++++++++------
> 1 file changed, 43 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/thermal/devfreq_cooling.c b/drivers/thermal/devfreq_cooling.c
> index 7063ccb7b86d..cf045bd4d16b 100644
> --- a/drivers/thermal/devfreq_cooling.c
> +++ b/drivers/thermal/devfreq_cooling.c
> @@ -227,6 +227,24 @@ static inline unsigned long get_total_power(struct devfreq_cooling_device *dfc,
> voltage);
> }
>
> +static void _normalize_load(struct devfreq_dev_status *status)
Is there a reason for the leading "_" ?
AFAIK, "__name()" is meant to suggest a "worker" function for another
"name()" function, but that would not apply here.
> +{
> + /* Make some space if needed */
> + if (status->busy_time > 0xffff) {
> + status->busy_time >>= 10;
> + status->total_time >>= 10;
> + }
How about removing the above code and adding here:
status->busy_time = status->busy_time ? : 1;
> +
> + if (status->busy_time > status->total_time)
This check would then cover the possibility that total_time is 0.
> + status->busy_time = status->total_time;
But a reversal is needed here:
status->total_time = status->busy_time;
> +
> + status->busy_time *= 100;
> + status->busy_time /= status->total_time ? : 1;
> +
> + /* Avoid division by 0 */
> + status->busy_time = status->busy_time ? : 1;
> + status->total_time = 100;
Then all of this code can be replaced by:
status->busy_time = (unsigned long)div64_u64((u64)status->busy_time << 10,
status->total_time);
status->total_time = 1 << 10;
This way you gain some resolution to busy_time and the divisions in the
callers would just become shifts by 10.
Hope it helps,
Ionela.
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next prev parent reply other threads:[~2020-10-07 16:49 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-21 12:20 [PATCH 0/5] Thermal devfreq cooling improvements with Energy Model Lukasz Luba
2020-09-21 12:20 ` [PATCH 1/5] thermal: devfreq_cooling: change tracing function and arguments Lukasz Luba
2020-09-21 12:20 ` [PATCH 2/5] thermal: devfreq_cooling: get a copy of device status Lukasz Luba
2020-10-07 16:11 ` Ionela Voinescu [this message]
2020-10-22 10:55 ` Lukasz Luba
2020-12-01 10:36 ` Ionela Voinescu
2020-12-01 12:19 ` Lukasz Luba
2020-12-01 14:55 ` Ionela Voinescu
2020-10-14 14:34 ` Daniel Lezcano
2020-10-22 11:45 ` Lukasz Luba
2020-09-21 12:20 ` [PATCH 3/5] thermal: devfreq_cooling: add new registration functions with Energy Model Lukasz Luba
2020-10-07 12:07 ` Ionela Voinescu
2020-10-22 11:17 ` Lukasz Luba
2020-12-01 14:05 ` Ionela Voinescu
2020-12-01 14:37 ` Lukasz Luba
2020-12-01 15:02 ` Ionela Voinescu
2020-09-21 12:20 ` [PATCH 4/5] thermal: devfreq_cooling: remove old power model and use EM Lukasz Luba
2020-10-07 15:12 ` Ionela Voinescu
2020-10-22 11:26 ` Lukasz Luba
2020-09-21 12:20 ` [PATCH 5/5] drm/panfrost: Register devfreq cooling and attempt to add Energy Model Lukasz Luba
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