linux-kernel - Re: [PATCH v2 5/6] drm/etnaviv: Add PPU flop reset

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Message-ID: <424c7fbf417c6d13c5842d78e83d72f705e021f1.camel@pengutronix.de>
Date: Mon, 23 Jun 2025 14:25:01 +0200
From: Lucas Stach <l.stach@...gutronix.de>
To: Gert Wollny <gert.wollny@...labora.com>, Russell King
 <linux+etnaviv@...linux.org.uk>, Christian Gmeiner
 <christian.gmeiner@...il.com>
Cc: etnaviv@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/6] drm/etnaviv: Add PPU flop reset

Am Montag, dem 23.06.2025 um 14:05 +0200 schrieb Gert Wollny:
> On Fri, 2025-06-20 at 22:22 +0200, Lucas Stach wrote:
> > 
> > > @@ -1807,6 +1808,11 @@ static int etnaviv_gpu_bind(struct device
> > > *dev, struct device *master,
> > >  		ret = -ENXIO;
> > >  		goto out_sched;
> > >  	}
> > > +
> > > +	if (etnaviv_flop_reset_ppu_require(&gpu->identity) &&
> > > +	    !priv->flop_reset_data_ppu)
> > > +		etnaviv_flop_reset_ppu_init(priv);
> > > +
> > I don't see why you would need to do this in the bind callback. You
> > should be able to move this to etnaviv_gpu_init(), so you have the
> > needed identification data. gpu_init is also executed serially over
> > all GPUs in the device, so there is no problem with potential races
> > there.
> 
> I moved this here because you wrote before: 
> 
> > But then you should allocate this buffer
> > in etnaviv_gpu_bind to avoid races between GPUs starting up and 
> > trying to allocate this global memory.
> 
Yea, sorry about this. I hadn't noticed the dependency on the HW
identification when I wrote this.

> If etnaviv_gpu_init() is fine, I'll move it there. 

I'm not saying that I may not again miss some implicit dependency, but
as far as I can see right now moving it there should be fine.
gpu_init() fulfills the same properties with regard to init ordering
between the GPUs as gpu_bind().

Regards,
Lucas