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From:   Adam Ford <aford173@gmail.com>
Date:   Thu, 3 Aug 2023 21:42:41 -0500
Message-ID: <CAHCN7xKnRAmKh60dAtVaxz-dQtjzhBNtS0aN2swmddfo5FAD-Q@mail.gmail.com>
Subject: Re: drivers/gpu/drm/bridge/samsung-dsim.c link error
To:     Randy Dunlap <rdunlap@infradead.org>
Cc:     Aleksandr Nogikh <nogikh@google.com>, l.stach@pengutronix.de,
        inki.dae@samsung.com, jagan@amarulasolutions.com,
        m.szyprowski@samsung.com, airlied@gmail.com, daniel@ffwll.ch,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        syzkaller@googlegroups.com, dvyukov@google.com
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On Thu, Aug 3, 2023 at 9:37=E2=80=AFPM Randy Dunlap <rdunlap@infradead.org>=
 wrote:
>
>
>
> On 8/3/23 19:26, Adam Ford wrote:
> > On Thu, Aug 3, 2023 at 9:01=E2=80=AFPM Randy Dunlap <rdunlap@infradead.=
org> wrote:
> >>
> >> Hi--
> >>
> >> On 8/3/23 08:24, Adam Ford wrote:
> >>> On Thu, Aug 3, 2023 at 9:42=E2=80=AFAM Aleksandr Nogikh <nogikh@googl=
e.com> wrote:
> >>>>
> >>>> Hello,
> >>>>
> >>>> We've been seing the following linker error on arm64 syzbot instance=
s:
> >>>>
> >>>> ld.lld: error: undefined symbol: phy_mipi_dphy_get_default_config_fo=
r_hsclk
> >>>>>>> referenced by samsung-dsim.c:731 (drivers/gpu/drm/bridge/samsung-=
dsim.c:731)
> >>>>>>>               drivers/gpu/drm/bridge/samsung-dsim.o:(samsung_dsim=
_init) in archive vmlinux.a
> >>>>
> >>>> Steps to reproduce on the latest linux-next:
> >>>>
> >>>> $ git checkout next-20230803
> >>>> $ wget -O '.config' 'https://raw.githubusercontent.com/google/syzkal=
ler/master/dashboard/config/linux/upstream-arm64-kasan.config'
> >>>> $ make CC=3Dclang ARCH=3Darm64 LD=3Dld.lld CROSS_COMPILE=3Daarch64-l=
inux-gnu- olddefconfig
> >>>>
> >>>> This also prints:
> >>>>
> >>>> WARNING: unmet direct dependencies detected for GENERIC_PHY_MIPI_DPH=
Y
> >>>>   Depends on [n]: GENERIC_PHY [=3Dn]
> >>>>   Selected by [y]:
> >>>>   - DRM_NWL_MIPI_DSI [=3Dy] && DRM_BRIDGE [=3Dy] && DRM [=3Dy] && CO=
MMON_CLK [=3Dy] && OF [=3Dy] && HAS_IOMEM [=3Dy]
> >>>>   - DRM_SAMSUNG_DSIM [=3Dy] && DRM [=3Dy] && DRM_BRIDGE [=3Dy] && CO=
MMON_CLK [=3Dy] && OF [=3Dy] && HAS_IOMEM [=3Dy]
> >>>>
> >>>> $ make CC=3Dclang ARCH=3Darm64 LD=3Dld.lld CROSS_COMPILE=3Daarch64-l=
inux-gnu- -j$(nproc)
> >>>>
> >>>> The kernel should have still compiled fine even despite the message =
above, right?
> >>
> >> No. See drivers/Makefile:
> >> obj-$(CONFIG_GENERIC_PHY)       +=3D phy/
> >>
> >> so the drivers/phy/ subdir is only built when CONFIG_GENERIC_PHY is se=
t,
> >> but it's not set.
> >>
> >>>> Could you please take a look?
> >>>
> >>> GENERIC_PHY_MIPI_DPHY was enabled to use
> >>> phy_mipi_dphy_get_default_config() which takes in the pixel clock,
> >>> bits-per-pixel, number of lanes and phy structure.  It applies a bunc=
h
> >>> of math based on the info passed and fills in the structure, but that
> >>> function itself doesn't appear to be referencing phy code, so it's
> >>> likely safe.
> >>>
> >>> I think this can be resolved by enabling GENERIC_PHY.  I just checked
> >>> linux-next and when I built the arm64 defconfig, it enables
> >>> GENERIC_PHY=3Dy, so I don't think this is an issue.  I also checked t=
he
> >>
> >> defconfig doesn't matter in this case. The .config that was provided h=
as:
> >> # CONFIG_GENERIC_PHY is not set
> >> CONFIG_GENERIC_PHY_MIPI_DPHY=3Dy
> >>
> >
> > Where/how was the .config generated?
> >
>
> Aleksandr posted a link to the config file above.

I get that, but I am not sure how this was generated.

>
> > Are you building linux-next or something else?  The .config file
> > generated when I build the arm64 defconfig  show both enabled:
>
> linux-next.
>
>
> > $ grep GENERIC_PHY .config
> > CONFIG_GENERIC_PHY=3Dy
> > CONFIG_GENERIC_PHY_MIPI_DPHY=3Dy
> >
>
> Yes, this is not a defconfig file.

I know, but it is a .config file that is generated from make defconfig
ARCH=3Darm64
>
> >
> >> but yes, selecting GENERIC_PHY (needed in 3 places) does fix the warni=
ngs
> >> and build error.  2 instance in drm/bridge/Kconfig and one in
> >> drm/bridge/cadence/Kconfig (found by inspection).
> >>
> >>
> >>
> >>> multi_v7_defconfig for ARM and it also sets GENERIC_PHY=3Dy for 32-bi=
t
> >>> ARM people using some of the Exynos boards.
> >>>
> >>> I don't know what version of Linux you're trying to build, but I can'=
t
> >>> replicate your issue.
> >>
> >> I had no problem replicating the kconfig warnings and build error.
> >
> > If you can replicate the problem, I'd suggest submitting a patch.
>
> Sure, I'll do that.

Great!  thanks.

adam
>
> --
> ~Randy