linux-kernel - Re: [Freedreno] [PATCH] drm/msm: Make DRM

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Date:   Wed, 7 Aug 2019 21:01:09 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Rob Clark <robdclark@...il.com>,
        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'

Hi Jordan/Rob.

On Wed, Aug 07, 2019 at 12:46:49PM -0600, Jordan Crouse wrote:
> 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
That would be best. So the defconfigs end up with the same config as
before.

> 
> 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.
"in every" equals three defconfigs:
$ git grep ARCH_QCOM | grep defconfig
arch/arm/configs/multi_v7_defconfig:CONFIG_ARCH_QCOM=y
arch/arm/configs/qcom_defconfig:CONFIG_ARCH_QCOM=y
arch/arm64/configs/defconfig:CONFIG_ARCH_QCOM=y

	Sam