linux-kernel - Re: [Freedreno] [PATCH] drm/msm: Make DRM_MSM default to 'm'

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Message-ID: <20190807184648.GA30521@jcrouse1-lnx.qualcomm.com>
Date:   Wed, 7 Aug 2019 12:46:49 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     Sam Ravnborg <sam@...nborg.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        David Airlie <airlied@...ux.ie>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Sean Paul <sean@...rly.run>
Subject: Re: [Freedreno] [PATCH] drm/msm: Make DRM_MSM default to 'm'

On Wed, Aug 07, 2019 at 11:08:53AM -0700, Rob Clark wrote:
> On Wed, Aug 7, 2019 at 10:38 AM Sam Ravnborg <sam@...nborg.org> wrote:
> >
> > Hi Jordan.
> > On Wed, Aug 07, 2019 at 11:24:27AM -0600, Jordan Crouse wrote:
> > > Most use cases for DRM_MSM will prefer to build both DRM and MSM_DRM as
> > > modules but there are some cases where DRM might be built in for whatever
> > > reason and in those situations it is preferable to still keep MSM as a
> > > module by default and let the user decide if they _really_ want to build
> > > it in.
> > >
> > > Additionally select QCOM_COMMAND_DB for ARCH_QCOM targets to make sure
> > > it doesn't get missed when we need it for a6xx tarets.
> > >
> > > Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>
> > > ---
> > >
> > >  drivers/gpu/drm/msm/Kconfig | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/Kconfig b/drivers/gpu/drm/msm/Kconfig
> > > index 9c37e4d..3b2334b 100644
> > > --- a/drivers/gpu/drm/msm/Kconfig
> > > +++ b/drivers/gpu/drm/msm/Kconfig
> > > @@ -14,11 +14,12 @@ config DRM_MSM
> > >       select SHMEM
> > >       select TMPFS
> > >       select QCOM_SCM if ARCH_QCOM
> > > +     select QCOM_COMMAND_DB if ARCH_QCOM
> > >       select WANT_DEV_COREDUMP
> > >       select SND_SOC_HDMI_CODEC if SND_SOC
> > >       select SYNC_FILE
> > >       select PM_OPP
> > > -     default y
> > > +     default m
> >
> > As a general comment the right thing would be to drop this default.
> > As it is now the Kconfig says that when DRM is selected then all of the
> > world would then also get DRM_MSM, which only a small part of this world
> > you see any benefit in.
> > So they now have to de-select MSM.
> 
> If the default is dropped, it should probably be accompanied by adding
> CONFIG_DRM_MSM=m to defconfig's, I think

In general I prefer to not use a default but this is the only GPU driver for
ARCH_QCOM and I think its safe to stay that 99% of ARCH_QCOM users would select
this module and those that wouldn't will omit DRM entirely.

I feel it is net negative if we dropped the default but then had to turn around
and enable it in every defconfig.

Jordan

> BR,
> -R
> 
> > Kconfig has:
> >     depends on ARCH_QCOM || SOC_IMX5 || (ARM && COMPILE_TEST)
> >
> > So maybe not all of the world but all QCOM or IMX5 users. Maybe they are all
> > interested in MSM. Otherwise the default should rather be dropped.
> > If there is any good hints then the help text could anyway use some
> > love, and then add the info there.
> >
> > The other change with QCOM_COMMAND_DB seems on the other hand to make
> > sense but then this is another patch.
> >
> >         Sam
> > _______________________________________________
> > Freedreno mailing list
> > Freedreno@...ts.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/freedreno

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