linux-kernel - Re: [PATCH] drm/imagination: DRM_POWERVR should depend on ARCH

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Date:   Wed, 29 Nov 2023 10:22:57 +0100
From:   Maxime Ripard <mripard@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Javier Martinez Canillas <javierm@...hat.com>,
        Frank Binns <frank.binns@...tec.com>,
        Donald Robson <donald.robson@...tec.com>,
        Matt Coster <matt.coster@...tec.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Sarah Walker <sarah.walker@...tec.com>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] drm/imagination: DRM_POWERVR should depend on ARCH_K3

On Wed, Nov 29, 2023 at 09:58:12AM +0100, Geert Uytterhoeven wrote:
> Hi Maxime,
> 
> On Wed, Nov 29, 2023 at 9:35 AM Maxime Ripard <mripard@...nel.org> wrote:
> > On Tue, Nov 28, 2023 at 08:16:18PM +0100, Geert Uytterhoeven wrote:
> > > On Tue, Nov 28, 2023 at 8:03 PM Javier Martinez Canillas
> > > <javierm@...hat.com> wrote:
> > > > Geert Uytterhoeven <geert+renesas@...der.be> writes:
> > > > > The Imagination Technologies PowerVR Series 6 GPU is currently only
> > > > > supported on Texas Instruments K3 AM62x SoCs.  Hence add a dependency on
> > > > > ARCH_K3, to prevent asking the user about this driver when configuring a
> > > > > kernel without Texas Instruments K3 Multicore SoC support.
> > > > >
> > > > > Fixes: 4babef0708656c54 ("drm/imagination: Add skeleton PowerVR driver")
> > > > > Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> 
> > > > In any case, I agree with you that restricting to only K3 makes sense.
> > >
> > > I am looking forward to adding || SOC_AM33XX || ARCH_RENESAS || ...,
> > > eventually ;-)
> >
> > I disagree. This is to handle a generic IP, just like panfrost, lima, or
> > etnaviv, and we certaintly don't want to maintain the Kconfig list of
> > every possible architecture and SoC family it might or might not be
> > found.
> 
> While PowerVR is a generic IP, I believe it needs a non-generic
> firmware, which is currently only available for AM62x SoCs.

I'm not sure it's actually true, but let's consider it is. Then what? If
the firmware isn't there and/or the DT bits too, then nothing will
happen. We would have wasted a couple of 100kB on a system that is
taking somewhere in the 100MB-10GB range, and that's pretty much it.

If you have we take that patch in though, we have:

  - To keep merging patches as firmwares become available.

  - If we update linux-firmware only, then the driver is still not
    loading even though it could.

  - If we have gotten our firmware through some other mean, then the
    driver is still not loading even though it could.

It makes life harder for everyone: maintainers, users, devs, based on
the state of some external project that might or might not be updated in
sync.

> Once it becomes truly generic, I'm happy to drop all platform
> dependencies.  Until then, there is no point in asking everyone who
> configures an arm64 kernel about this driver, unless they also enabled
> K3 support.

Whether it's truly generic, whatever that means, is irrelevant here.

Maxime

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