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

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Hi,

On 05/09/23 16:40, Dmitry Baryshkov wrote:
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";
};

The above works. Thanks.


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.


Should it be,
&{/soc@0/usb} {
	dr_mode = "host";
};

I will send a v3 version for this. Thank you.

Regards,
Vignesh



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