linux-kernel - Re: [PATCH v1 0/2] Add waveshare 7inch touchscreen panel support

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Message-ID: <dab03c60-caa9-47e3-9dac-fa499227b67b@gmx.net>
Date:   Fri, 24 Nov 2023 15:54:32 +0100
From:   Stefan Wahren <wahrenst@....net>
To:     Shengyang Chen <shengyang.chen@...rfivetech.com>,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org
Cc:     neil.armstrong@...aro.org, quic_jesszhan@...cinc.com,
        sam@...nborg.org, airlied@...il.com, daniel@...ll.ch,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        florian.fainelli@...adcom.com,
        bcm-kernel-feedback-list@...adcom.com, emma@...olt.net,
        thierry.reding@...il.com, changhuang.liang@...rfivetech.com,
        keith.zhao@...rfivetech.com, jack.zhu@...rfivetech.com,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/2] Add waveshare 7inch touchscreen panel support

Hi Shengyang,

[fix address of Emma]

Am 24.11.23 um 11:44 schrieb Shengyang Chen:
> This patchset adds waveshare 7inch touchscreen panel support
> for the StarFive JH7110 SoC.
>
> Patch 1 add new compatible for the raspberrypi panel driver and its dt-binding.
> Patch 2 add new display mode and new probing process for raspberrypi panel driver.
>
> Waveshare 7inch touchscreen panel is a kind of raspberrypi panel
> which can be drived by raspberrypi panel driver.
>
> The series has been tested on the VisionFive 2 board.
surprisingly i was recently working on the official Raspberry Pi
touchscreen and was able to get it running the new way.

What do i mean with the new way. There is almost nothing special to the
Raspberry Pi touchscreen, so we should try to use/extend existing
components like:

CONFIG_DRM_PANEL_SIMPLE
CONFIG_TOUCHSCREEN_EDT_FT5X06
CONFIG_DRM_TOSHIBA_TC358762

The only special part is the Attiny on the connector PCB which requires:

CONFIG_REGULATOR_RASPBERRYPI_TOUCHSCREEN_ATTINY

So the whole point is to avoid writing monolitic drivers for simple
panel like that.

There is a WIP branch based on top of Linux 6.7-rcX, which should
demonstrate this approach [1]. Unfortunately it is not ready for
upstreaming, but it has been tested on a Raspberry Pi 3 B Plus. Maybe
this is helpful for your case.

Actually i consider panel-raspberrypi-touchscreen.c as a dead end, which
shouldn't be extended.

Btw there are already DT overlays in mainline which seems to use the
Raspberry Pi 7inch panel (without touch function yet) [2].

[1] - https://github.com/lategoodbye/rpi-zero/commits/v6.7-7inch-ts
[2] -
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/arch/arm64/boot/dts/freescale/imx8mm-venice-gw72xx-0x-rpidsi.dtso?h=v6.6.2&id=6b4da1354fd81adace0cda448c77d8f2a47d8474

>
> Shengyang Chen (2):
>    dt-bindings: display: panel: raspberrypi: Add compatible property for
>      waveshare 7inch touchscreen panel
>    gpu: drm: panel: raspberrypi: add new display mode and new probing
>      process
>
>   .../panel/raspberrypi,7inch-touchscreen.yaml  |  4 +-
>   .../drm/panel/panel-raspberrypi-touchscreen.c | 99 ++++++++++++++++---
>   2 files changed, 91 insertions(+), 12 deletions(-)
>