linux-kernel - Re: [RFC PATCH 0/3] gpu: nova-core: add basic timer subdevice implementation

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Message-ID: <CAPM=9txa5Uo0qC-5OqNOcrWaGNjJEr8+J+ug0C3e6fMk9t18Zg@mail.gmail.com>
Date: Fri, 28 Feb 2025 12:24:50 +1000
From: Dave Airlie <airlied@...il.com>
To: Timur Tabi <ttabi@...dia.com>
Cc: Alexandre Courbot <acourbot@...dia.com>, 
	"nouveau-bounces@...ts.freedesktop.org" <nouveau-bounces@...ts.freedesktop.org>, John Hubbard <jhubbard@...dia.com>, 
	"gary@...yguo.net" <gary@...yguo.net>, 
	"rust-for-linux@...r.kernel.org" <rust-for-linux@...r.kernel.org>, 
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"boqun.feng@...il.com" <boqun.feng@...il.com>, "dakr@...nel.org" <dakr@...nel.org>, 
	"nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>, 
	"joel@...lfernandes.org" <joel@...lfernandes.org>, Ben Skeggs <bskeggs@...dia.com>
Subject: Re: [RFC PATCH 0/3] gpu: nova-core: add basic timer subdevice implementation

On Fri, 28 Feb 2025 at 11:49, Timur Tabi <ttabi@...dia.com> wrote:
>
> On Fri, 2025-02-28 at 07:37 +1000, Dave Airlie wrote:
> > I've tried to retrofit checking 0xffffffff to drivers a lot, I'd
> > prefer not to. Drivers getting stuck in wait for clear bits for ever.
>
> That's what read_poll_timeout() is for.  I'm surprised Nouveau doesn't use it.

That doesn't handle the PCIE returns 0xffffffff case at all, which is
the thing we most want to handle, it also uses the CPU timer whereas
nouveau's wait infrastructure uses the GPU timer usually (though that
could be changed).

Dave.