Re: [PATCH v2 2/7] drm: ci: Force db410c to host mode

[Dmitry Baryshkov]

On Tue, 5 Sept 2023 at 14:00, Maxime Ripard <mripard@xxxxxxxxxx> wrote:
>
> On Tue, Sep 05, 2023 at 03:39:33PM +0530, Vignesh Raman wrote:
> > Hi Dmitry, Maxime,
> >
> > On 05/09/23 14:13, Maxime Ripard wrote:
> > > Hi,
> > >
> > > On Mon, Sep 04, 2023 at 07:59:26PM +0300, Dmitry Baryshkov wrote:
> > > > On Mon, 4 Sept 2023 at 19:16, Vignesh Raman <vignesh.raman@xxxxxxxxxxxxx> wrote:
> > > > >
> > > > > Force db410c to host mode to fix network issue which results in failure
> > > > > to mount root fs via NFS.
> > > > > See https://gitlab.freedesktop.org/gfx-ci/linux/-/commit/cb72a629b8c15c80a54dda510743cefd1c4b65b8
> > > > >
> > > > > Use fdtoverlay command to merge base device tree with an overlay
> > > > > which contains the fix for USB controllers to work in host mode.
> > > > >
> > > > > Signed-off-by: Vignesh Raman <vignesh.raman@xxxxxxxxxxxxx>
> > > > > ---
> > > > >
> > > > > v2:
> > > > >    - Use fdtoverlay command to merge overlay dtbo with the base dtb instead of modifying the kernel sources
> > > > >
> > > > > ---
> > > > >   drivers/gpu/drm/ci/build.sh                         |  5 +++++
> > > > >   .../gpu/drm/ci/dt-overlays/apq8016-sbc-overlay.dts  | 13 +++++++++++++
> > > > >   2 files changed, 18 insertions(+)
> > > > >   create mode 100644 drivers/gpu/drm/ci/dt-overlays/apq8016-sbc-overlay.dts
> > > > >
> > > > > diff --git a/drivers/gpu/drm/ci/build.sh b/drivers/gpu/drm/ci/build.sh
> > > > > index 7b014287a041..92ffd98cd09e 100644
> > > > > --- a/drivers/gpu/drm/ci/build.sh
> > > > > +++ b/drivers/gpu/drm/ci/build.sh
> > > > > @@ -92,6 +92,11 @@ done
> > > > >
> > > > >   if [[ -n ${DEVICE_TREES} ]]; then
> > > > >       make dtbs
> > > > > +    if [[ -e arch/arm64/boot/dts/qcom/apq8016-sbc.dtb ]]; then
> > > > > +        dtc -@ -I dts -O dtb -o drivers/gpu/drm/ci/dt-overlays/apq8016-sbc-overlay.dtbo drivers/gpu/drm/ci/dt-overlays/apq8016-sbc-overlay.dts
> > > > > +        fdtoverlay -i arch/arm64/boot/dts/qcom/apq8016-sbc.dtb -o arch/arm64/boot/dts/qcom/apq8016-sbc-overlay.dtb drivers/gpu/drm/ci/dt-overlays/apq8016-sbc-overlay.dtbo
> > > > > +        mv arch/arm64/boot/dts/qcom/apq8016-sbc-overlay.dtb arch/arm64/boot/dts/qcom/apq8016-sbc.dtb
> > > > > +    fi
> > > > >       cp ${DEVICE_TREES} /lava-files/.
> > > > >   fi
> > > > >
> > > > > diff --git a/drivers/gpu/drm/ci/dt-overlays/apq8016-sbc-overlay.dts b/drivers/gpu/drm/ci/dt-overlays/apq8016-sbc-overlay.dts
> > > > > new file mode 100644
> > > > > index 000000000000..57b7604f1c23
> > > > > --- /dev/null
> > > > > +++ b/drivers/gpu/drm/ci/dt-overlays/apq8016-sbc-overlay.dts
> > > > > @@ -0,0 +1,13 @@
> > > > > +/dts-v1/;
> > > > > +/plugin/;
> > > > > +
> > > > > +/ {
> > > > > +    fragment@0 {
> > > > > +        target-path = "/soc@0";
> > > > > +        __overlay__ {
> > > > > +            usb@78d9000 {
> > > > > +                dr_mode = "host";
> > > > > +            };
> > > > > +        };
> > > > > +    };
> > > > > +};
> > > > > --
> > > > > 2.40.1
> > > >
> > > > Can we use normal dtso syntax here instead of defining fragments manually?
> > >
> > > What Dmitry is hinting about is to use the "Sugar Syntax". There a good documentation here:
> > > https://source.android.com/docs/core/architecture/dto/syntax
> >
> >
> > With the below DTO syntax,
> > /dts-v1/;
> > /plugin/;
> >
> > &usb {
> >   usb@78d9000 {
> >     dr_mode = "host";
> >   };
> > };
> >
> > Decoded dtbo file is,
> > /dts-v1/;
> >
> > / {
> >
> >       fragment@0 {
> >               target = <0xffffffff>;
> >
> >               __overlay__ {
> >
> >                       usb@78d9000 {
> >                               dr_mode = "host";
> >                       };
> >               };
> >       };
> >
> >       __fixups__ {
> >               usb = "/fragment@0:target:0";
> >       };
> > };
> >
> > With the previous fix using fragment we get,
> > / {
> >
> >       fragment@0 {
> >               target-path      = "/soc@0";
> >
> >               __overlay__ {
> >
> >                       usb@78d9000 {
> >                               dr_mode = "host";
> >                       };
> >               };
> >       };
> > };
> >
> > Decoded apq8016-sbc.dtb file with the fix (setting dr_mode to host) is,
> > /dts-v1/;
> > / {
> >       soc@0 {
> >               usb@78d9000 {
> >                       dr_mode = "host";
> >               };
> >       };
> > };
> >
> > How can set the target to "soc@0" using the DTO syntax?
>
> To strictly answer your question, that would be something like
>
> &{/soc@0} {
>         usb@78d9000 {
>                 dr_mode = "host";
>         };
> };
>
> You can simplify this further however by doing:
>
>
> &{/soc@0/usb@78d9000} {
>         dr_mode = "host";
> };
>
> Also, that node actually has a label ("usb"), defined here:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/qcom/msm8916.dtsi#n2322
>
> So you can end up with
>
> &usb {
>         dr_mode = "host";
> };

... which is the simplest and thus more robust one.

> All of them should be equivalent to the one you had in your patch.
>
> Maxime

-- 
With best wishes
Dmitry