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

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Message-ID: <CAPM=9txkwr3_sdNESa9ufu1j4V-XsJ=EuLFuNLb_dLCfwhYD3w@mail.gmail.com>
Date: Wed, 26 Feb 2025 08:42:35 +1000
From: Dave Airlie <airlied@...il.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Joel Fernandes <joelagnelf@...dia.com>, Alexandre Courbot <acourbot@...dia.com>, 
	Gary Guo <gary@...yguo.net>, Joel Fernandes <joel@...lfernandes.org>, 
	Boqun Feng <boqun.feng@...il.com>, John Hubbard <jhubbard@...dia.com>, 
	Ben Skeggs <bskeggs@...dia.com>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, nouveau@...ts.freedesktop.org, 
	dri-devel@...ts.freedesktop.org, paulmck@...nel.org, 
	Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [RFC PATCH 0/3] gpu: nova-core: add basic timer subdevice implementation

>
> I'm saying that extending the time of critical sections is a concern, because
> it's more likely to miss the unplug event and it's just not necessary. You grab
> the guard, do a few I/O ops and drop it -- simple.

At least for nova-core I've realised I got this partly wrong,

https://gitlab.freedesktop.org/nouvelles/kernel/-/blob/nova-core-experiments/drivers/gpu/nova-core/falcon.rs?ref_type=heads#L305

However in this case I expect the sleeps small enough to end up in
udelay perhaps instead of actual sleeps,

but I wouldn't be too worried about the overhead of adding a bit of
extra code in the wake up from sleep path, the sleep is going to take
the time, a few extra instructions in the poll won't be noticeable.

Dave.