Re: [RFC PATCH] ARM: dts: imx53-qsb: Add MCIMX-LVDS1 display module support

From: Liu Ying
Date: Mon Jul 29 2024 - 00:47:44 EST

Hi Dmitry,

On 07/27/2024, Dmitry Baryshkov wrote:
> On Fri, Jul 26, 2024 at 02:50:12PM GMT, Liu Ying wrote:
>> MCIMX-LVDS1[1] display module integrates a HannStar HSD100PXN1 LVDS
>> display panel and a touch IC. Add an overlay to support the LVDS
>> panel on i.MX53 QSB / QSRB platforms.
>>
>> [1] https://www.nxp.com/part/MCIMX-LVDS1
>>
>> Signed-off-by: Liu Ying <victor.liu@xxxxxxx>
>> ---
>> I mark RFC in patch subject prefix because if the DT overlay is used, both ldb
>> and panel devices end up as devices deferred. However, if the DT overlay is
>> not used and the devices are defined in imx53-qsb-common.dtsi, then they can be
>> probed ok.
>>
>> With a dev_err_probe() added to imx_ldb_probe() in imx-ldb.c, devices_deferred
>> indicates 53fa8008.ldb and panel-lvds kind of depend on each other.
>>
>> root@imx53qsb:~# cat /sys/kernel/debug/devices_deferred
>> 53fa8008.ldb imx-ldb: failed to find panel or bridge for channel0
>> panel-lvds platform: wait for supplier /soc/bus@50000000/ldb@53fa8008/lvds-channel@0
>>
>> It looks like the issue is related to fw_devlink, because if "fw_devlink=off"
>> is added to kernel bootup command line, then the issue doesn't happen.
>
> Could you please fdtdump /sys/firmware/fdt (or just generated DTB files)
> in both cases and compare the dumps for sensible differences?

I fdtdump imx53-qsrb-mcimx-lvds1.dtb and imx53-qsrb.dtb.

I see three sensible differences.
1) panel-lvds node position.
For imx53-qsrb-mcimx-lvds1.dtb, it comes very early and is next to
'compatible = "fsl,imx53-qsrb", "fsl,imx53";'.
For imx53-qsrb.dtb, it comes later and is next to panel node in '/' node.

2) properties order in panel-lvds node.
For imx53-qsrb-mcimx-lvds1.dtb, it shows
panel-lvds {
power-supply = <0x0000001c>;
backlight = <0x00000030>;
compatible = "hannstar,hsd100pxn1";
port {
endpoint {
phandle = <0x0000007d>;
remote-endpoint = <0x0000007c>;
};
};
};
For imx53-qsrb.dtb, it shows
panel-lvds {
compatible = "hannstar,hsd100pxn1";
backlight = <0x00000031>;
power-supply = <0x0000001d>;
port {
endpoint {
remote-endpoint = <0x00000033>;
phandle = <0x00000017>;
};
};
};

3) No 'lvds0_out' and 'panel_lvds_in' in __symbols__ node for
imx53-qsrb-mcimx-lvds1.dtb, but for imx53-qsrb.dtb they are in it.
lvds0_out = "/soc/bus@50000000/ldb@53fa8008/lvds-channel@0/port@2/endpoint";
panel_lvds_in = "/panel-lvds/port/endpoint";

BTW, reverting Saravana's commits
7cb50f6c9fba ("of: property: fw_devlink: Fix stupid bug in remote-endpoint parsing")
and/or
7fddac12c382 ("driver core: Fix device_link_flag_is_sync_state_only()")
avoids the issue from happening.

>
>>
>> Saravana, DT folks, any ideas?
>>
>> Thanks.
>>
>> arch/arm/boot/dts/nxp/imx/Makefile | 4 ++
>> .../boot/dts/nxp/imx/imx53-qsb-common.dtsi | 4 +-
>> .../dts/nxp/imx/imx53-qsb-mcimx-lvds1.dtso | 43 +++++++++++++++++++
>> 3 files changed, 49 insertions(+), 2 deletions(-)
>> create mode 100644 arch/arm/boot/dts/nxp/imx/imx53-qsb-mcimx-lvds1.dtso
>>
>> diff --git a/arch/arm/boot/dts/nxp/imx/Makefile b/arch/arm/boot/dts/nxp/imx/Makefile
>> index 92e291603ea1..7116889e1515 100644
>> --- a/arch/arm/boot/dts/nxp/imx/Makefile
>> +++ b/arch/arm/boot/dts/nxp/imx/Makefile
>> @@ -46,8 +46,10 @@ dtb-$(CONFIG_SOC_IMX53) += \
>> imx53-ppd.dtb \
>> imx53-qsb.dtb \
>> imx53-qsb-hdmi.dtb \
>> + imx53-qsb-mcimx-lvds1.dtb \
>> imx53-qsrb.dtb \
>> imx53-qsrb-hdmi.dtb \
>> + imx53-qsrb-mcimx-lvds1.dtb \
>> imx53-sk-imx53.dtb \
>> imx53-sk-imx53-atm0700d4-lvds.dtb \
>> imx53-sk-imx53-atm0700d4-rgb.dtb \
>> @@ -57,7 +59,9 @@ dtb-$(CONFIG_SOC_IMX53) += \
>> imx53-usbarmory.dtb \
>> imx53-voipac-bsb.dtb
>> imx53-qsb-hdmi-dtbs := imx53-qsb.dtb imx53-qsb-hdmi.dtbo
>> +imx53-qsb-mcimx-lvds1-dtbs := imx53-qsb.dtb imx53-qsb-mcimx-lvds1.dtbo
>> imx53-qsrb-hdmi-dtbs := imx53-qsrb.dtb imx53-qsb-hdmi.dtbo
>> +imx53-qsrb-mcimx-lvds1-dtbs := imx53-qsrb.dtb imx53-qsb-mcimx-lvds1.dtbo
>> dtb-$(CONFIG_SOC_IMX6Q) += \
>> imx6dl-alti6p.dtb \
>> imx6dl-apf6dev.dtb \
>> diff --git a/arch/arm/boot/dts/nxp/imx/imx53-qsb-common.dtsi b/arch/arm/boot/dts/nxp/imx/imx53-qsb-common.dtsi
>> index 05d7a462ea25..430792a91ccf 100644
>> --- a/arch/arm/boot/dts/nxp/imx/imx53-qsb-common.dtsi
>> +++ b/arch/arm/boot/dts/nxp/imx/imx53-qsb-common.dtsi
>> @@ -16,7 +16,7 @@ memory@70000000 {
>> <0xb0000000 0x20000000>;
>> };
>>
>> - backlight_parallel: backlight-parallel {
>> + backlight: backlight {
>
> Nit: this seems unrelated to the LVDS support

Do you suggest to do this in a separate patch?
If yes, is it worth adding a Fixes tag?

>
>> compatible = "pwm-backlight";
>> pwms = <&pwm2 0 5000000 0>;
>> brightness-levels = <0 4 8 16 32 64 128 255>;
>> @@ -89,7 +89,7 @@ panel_dpi: panel {
>> compatible = "sii,43wvf1g";
>> pinctrl-names = "default";
>> pinctrl-0 = <&pinctrl_display_power>;
>> - backlight = <&backlight_parallel>;
>> + backlight = <&backlight>;
>> enable-gpios = <&gpio3 24 GPIO_ACTIVE_HIGH>;
>>
>> port {
>> diff --git a/arch/arm/boot/dts/nxp/imx/imx53-qsb-mcimx-lvds1.dtso b/arch/arm/boot/dts/nxp/imx/imx53-qsb-mcimx-lvds1.dtso
>> new file mode 100644
>> index 000000000000..27f6bedf3d39
>> --- /dev/null
>> +++ b/arch/arm/boot/dts/nxp/imx/imx53-qsb-mcimx-lvds1.dtso
>> @@ -0,0 +1,43 @@
>> +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
>> +/*
>> + * Copyright 2024 NXP
>> + */
>> +
>> +/dts-v1/;
>> +/plugin/;
>> +
>> +&{/} {
>> + panel-lvds {
>
> Nit: Just 'panel' should be enough.

Nope.

'panel-lvds' is needed to differentiate it from 'panel' in
imx53-qsb-common.dtsi which is a DPI panel.

Using 'panel-lvds', procfs lists exactly the properties needed.
root@imx53qsb:~# ls /proc/device-tree/panel-lvds/
backlight compatible name port power-supply

Using 'panel', more are listed.
root@imx53qsb:~# ls /proc/device-tree/panel/
backlight compatible enable-gpios name phandle pinctrl-0 pinctrl-names port power-supply

>
>> + compatible = "hannstar,hsd100pxn1";
>> + backlight = <&backlight>;
>> + power-supply = <&reg_3p2v>;
>> +
>> + port {
>> + panel_lvds_in: endpoint {
>> + remote-endpoint = <&lvds0_out>;
>> + };
>> + };
>> + };
>> +};
>> +
>> +&ldb {
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> + status = "okay";
>> +
>> + lvds-channel@0 {
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> + fsl,data-mapping = "spwg";
>> + fsl,data-width = <18>;
>> + status = "okay";
>> +
>> + port@2 {
>> + reg = <2>;
>> +
>> + lvds0_out: endpoint {
>> + remote-endpoint = <&panel_lvds_in>;
>> + };
>> + };
>> + };
>> +};
>> --
>> 2.34.1
>>
>

--
Regards,
Liu Ying