linux-kernel - Re: [PATCH 0/5] drm/etnaviv: Ignore MC bit when checking for runtime suspend

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Date:   Thu, 25 Jun 2020 16:55:03 +0200
From:   Guido Günther <agx@...xcpu.org>
To:     Lucas Stach <l.stach@...gutronix.de>
Cc:     Russell King <linux+etnaviv@...linux.org.uk>,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, etnaviv@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] drm/etnaviv: Ignore MC bit when checking for runtime
 suspend

Hi,
On Tue, Mar 03, 2020 at 12:55:04PM +0100, Lucas Stach wrote:
> On Mo, 2020-03-02 at 20:13 +0100, Guido Günther wrote:
> > At least GC7000 fails to enter runtime suspend for long periods of time since
> > the MC becomes busy again even when the FE is idle. The rest of the series
> > makes detecting similar issues easier to debug in the future by checking
> > all known bits in debugfs and also warning in the EBUSY case.
> 
> Thanks, series applied to etnaviv/next.
> 
> > Tested on GC7000 with a reduced runtime delay of 50ms. Patches are
> > against next-20200226.
> 
> I've already wondered if 200ms is too long, 50ms sounds more
> reasonable. Do you have any numbers on the power draw on the i.MX8M
> with idle GPU, vs. being fully power gated?

The difference is at least 250mW. It makes a huge difference over here.
We hit
https://lore.kernel.org/dri-devel/20200614064601.7872-1-navid.emamdoost@gmail.com/
recently and you notice instantly when that happens when looking at the
SoC temperature.

Cheers,
 -- Guido
> 
> Regards,
> Lucas
> 
> > Thanks to Lucas Stach for pointing me in the right direction.
> > 
> > Guido Günther (5):
> >   drm/etnaviv: Fix typo in comment
> >   drm/etnaviv: Update idle bits
> >   drm/etnaviv: Consider all kwnown idle bits in debugfs
> >   drm/etnaviv: Ignore MC when checking runtime suspend idleness
> >   drm/etnaviv: Warn when GPU doesn't idle fast enough
> > 
> >  drivers/gpu/drm/etnaviv/etnaviv_gpu.c  | 26 ++++++++++++++++++++++----
> >  drivers/gpu/drm/etnaviv/state_hi.xml.h |  7 +++++++
> >  2 files changed, 29 insertions(+), 4 deletions(-)
> > 
>