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

[Vignesh Raman <vignesh.raman@collabora.com>]

Hi,

On 05/09/23 16:40, Dmitry Baryshkov wrote:
> On Tue, 5 Sept 2023 at 14:00, Maxime Ripard <mripard@kernel.org> 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@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";
>> };

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