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

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Message-ID: <2c812fe4-04ba-0243-5330-c7b7e695cff9@collabora.com>
Date:   Tue, 5 Sep 2023 15:39:33 +0530
From:   Vignesh Raman <vignesh.raman@...labora.com>
To:     Maxime Ripard <mripard@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     dri-devel@...ts.freedesktop.org, helen.koike@...labora.com,
        guilherme.gallo@...labora.com, sergi.blanch.torne@...labora.com,
        david.heidelberg@...labora.com, daniels@...labora.com,
        gustavo.padovan@...labora.com, emma@...olt.net,
        robclark@...edesktop.org, robdclark@...gle.com, anholt@...gle.com,
        robdclark@...il.com, airlied@...il.com, daniel@...ll.ch,
        jani.nikula@...ux.intel.com, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        virtualization@...ts.linux-foundation.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 2/7] drm: ci: Force db410c to host mode

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@...labora.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@...labora.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@...9000 {
>>> +                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@...9000 {
     dr_mode = "host";
   };
};

Decoded dtbo file is,
/dts-v1/;

/ {

	fragment@0 {
		target = <0xffffffff>;

		__overlay__ {

			usb@...9000 {
				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@...9000 {
				dr_mode = "host";
			};
		};
	};
};

Decoded apq8016-sbc.dtb file with the fix (setting dr_mode to host) is,
/dts-v1/;
/ {	
	soc@0 {
		usb@...9000 {
			dr_mode = "host";
		};	
	};
};

How can set the target to "soc@0" using the DTO syntax? Otherwise 
fdtoverlay fails to apply the dtbo file with the base dtb.

Regards,
Vignesh