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    SubjectRe: [PATCH v2 2/7] drm: ci: Force db410c to host mode
    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@collabora.com> 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@collabora.com>
    > > > > ---
    > > > >
    > > > > 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";
    };

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

    Maxime

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