linux-kernel - Re: [PATCH] arm64: dts: imx8mn-venice-gw7902: disable gpu

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Message-ID: <20220126115646.GM4686@dragon>
Date:   Wed, 26 Jan 2022 19:56:47 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Lucas Stach <l.stach@...gutronix.de>
Cc:     Tim Harvey <tharvey@...eworks.com>,
        Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Adam Ford <aford173@...il.com>
Subject: Re: [PATCH] arm64: dts: imx8mn-venice-gw7902: disable gpu

On Wed, Jan 26, 2022 at 10:58:56AM +0100, Lucas Stach wrote:
> Am Mittwoch, dem 26.01.2022 um 17:35 +0800 schrieb Shawn Guo:
> > On Thu, Dec 16, 2021 at 08:12:27AM -0800, Tim Harvey wrote:
> > > Since commit 99aa29932271 ("arm64: dts: imx8mn: Enable GPU")
> > > imx8mn-venice-gw7902 will hang during kernel init because it uses
> > > a MIMX8MN5CVTI which does not have a GPU.
> > 
> > I do not quite follow on this.  i.MX8MN integrates a GPU, and
> > MIMX8MN5CVTI is built on i.MX8MN, correct?  If so, how comes
> > MIMX8MN5CVTI doesn't have a GPU?
> > 
> It's a fused-down variant of the i.MX8MN that has the GPU disabled by
> fuses.
> 
> > > 
> > > Disable pgc_gpumix to work around this. We also disable the GPU devices
> > > that depend on the gpumix power domain and pgc_gpu to avoid them staying
> > > in a probe deferred state forever.
> > 
> > Is this an indication that GPU should be disabled in imx8mn.dtsi and
> > enabled board by board?
> > 
> There's a trade-off here: most boards will probably use the full
> variants that include the GPU, so probably less boards will need to
> disable the GPU, as done here, than boards that need to enable it when
> the base DT disables the GPU.
> 
> Same story as with the i.MX6 where there are some SKUs that disable the
> VPU by fuses: we enable it in the base DT and if you happen to build a
> very low-cost board that uses the fused-down version you need to
> disable it in the board DT.

Thanks, Lucas!

Patch applied!

Shawn