From: "Clément Péron" <peron.clem@gmail.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Rob Herring <robh@kernel.org>,
Tomeu Vizoso <tomeu.vizoso@collabora.com>,
Steven Price <steven.price@arm.com>,
Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
Stephen Boyd <sboyd@kernel.org>,
Maxime Ripard <mripard@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 05/15] drm/panfrost: use spinlock instead of atomic
Date: Fri, 29 May 2020 14:35:08 +0200 [thread overview]
Message-ID: <CAJiuCcemwM-11ZT5+-4JfyTgTRD-_JjWz=HDCme8743M5Epf0g@mail.gmail.com> (raw)
In-Reply-To: <788ac664-e426-d307-f81e-9632de09887c@arm.com>
Hi Robin,
On Fri, 29 May 2020 at 14:20, Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 2020-05-10 17:55, Clément Péron wrote:
> > Convert busy_count to a simple int protected by spinlock.
>
> A little more reasoning might be nice.
I have follow the modification requested for lima devfreq and clearly
don't have any argument to switch to spinlock.
The Lima Maintainer asked to change witht the following reason :
"Better make this count a normal int which is also protected by the spinlock,
because current implementation can't protect atomic ops for state change
and busy idle check and we are using spinlock already"
>
> > Signed-off-by: Clément Péron <peron.clem@gmail.com>
> > ---
> [...]
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.h b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> > index 0697f8d5aa34..e6629900a618 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> > +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.h
> > @@ -4,6 +4,7 @@
> > #ifndef __PANFROST_DEVFREQ_H__
> > #define __PANFROST_DEVFREQ_H__
> >
> > +#include <linux/spinlock.h>
> > #include <linux/ktime.h>
> >
> > struct devfreq;
> > @@ -14,10 +15,17 @@ struct panfrost_device;
> > struct panfrost_devfreq {
> > struct devfreq *devfreq;
> > struct thermal_cooling_device *cooling;
> > +
> > ktime_t busy_time;
> > ktime_t idle_time;
> > ktime_t time_last_update;
> > - atomic_t busy_count;
> > + int busy_count;
> > + /*
> > + * Protect busy_time, idle_time, time_last_update and busy_count
> > + * because these can be updated concurrently, for example by the GP
> > + * and PP interrupts.
> > + */
>
> Nit: this comment is clearly wrong, since we only have Job, GPU and MMU
> interrupts here. I guess if there is a race it would be between
> submission/completion/timeout on different job slots.
It's copy/paste from lima I will update it,
>
> Given that, should this actually be considered a fix for 9e62b885f715
> ("drm/panfrost: Simplify devfreq utilisation tracking")?
I can't say if it can be considered as a fix, I didn't see any
improvement on my board before and after this patch.
I'm still facing some issue and didn't have time to fully investigate it.
Thanks for you review,
>
> Robin.
next prev parent reply other threads:[~2020-05-29 12:35 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-10 16:55 [PATCH 00/15][RFC] Add regulator devfreq support to Panfrost Clément Péron
2020-05-10 16:55 ` [PATCH 01/15] drm/panfrost: avoid static declaration Clément Péron
2020-05-28 13:22 ` Steven Price
2020-05-10 16:55 ` [PATCH 02/15] drm/panfrost: clean headers in devfreq Clément Péron
2020-05-28 13:22 ` Steven Price
2020-05-10 16:55 ` [PATCH 03/15] drm/panfrost: don't use pfdevfreq.busy_count to know if hw is idle Clément Péron
2020-05-28 13:22 ` Steven Price
2020-05-10 16:55 ` [PATCH 04/15] drm/panfrost: introduce panfrost_devfreq struct Clément Péron
2020-05-28 13:22 ` Steven Price
2020-05-10 16:55 ` [PATCH 05/15] drm/panfrost: use spinlock instead of atomic Clément Péron
2020-05-28 13:22 ` Steven Price
2020-05-29 12:20 ` Robin Murphy
2020-05-29 12:35 ` Clément Péron [this message]
2020-05-29 12:47 ` Steven Price
2020-05-10 16:55 ` [PATCH 06/15] drm/panfrost: properly handle error in probe Clément Péron
2020-05-28 13:22 ` Steven Price
2020-05-10 16:55 ` [PATCH 07/15] drm/panfrost: use device_property_present to check for OPP Clément Péron
2020-05-28 13:22 ` Steven Price
2020-05-29 12:45 ` Clément Péron
2020-05-10 16:55 ` [PATCH 08/15] drm/panfrost: move devfreq_init()/fini() in device Clément Péron
2020-05-28 13:22 ` Steven Price
2020-05-29 12:38 ` Clément Péron
2020-06-08 11:55 ` Tomeu Vizoso
2020-05-10 16:55 ` [PATCH 09/15] drm/panfrost: dynamically alloc regulators Clément Péron
2020-05-28 13:22 ` Steven Price
2020-05-10 16:55 ` [PATCH 10/15] drm/panfrost: add regulators to devfreq Clément Péron
2020-05-28 13:23 ` Steven Price
2020-05-29 12:37 ` Clément Péron
2020-05-10 16:55 ` [PATCH 11/15] drm/panfrost: set devfreq clock name Clément Péron
2020-05-28 13:23 ` Steven Price
2020-05-29 12:35 ` Clément Péron
2020-05-10 16:55 ` [PATCH 12/15] arm64: defconfig: Enable devfreq cooling device Clément Péron
2020-05-10 16:55 ` [PATCH 13/15] arm64: dts: allwinner: h6: Add cooling map for GPU Clément Péron
2020-05-10 16:55 ` [PATCH 14/15] [DO NOT MERGE] arm64: dts: allwinner: h6: Add GPU OPP table Clément Péron
2020-05-10 16:55 ` [PATCH 15/15] [DO NOT MERGE] arm64: dts: allwinner: force GPU regulator to be always Clément Péron
2020-05-11 5:43 ` [PATCH 00/15][RFC] Add regulator devfreq support to Panfrost Tomeu Vizoso
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