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

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Date:   Fri, 24 Nov 2023 16:04:47 +0000
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Stefan Wahren <wahrenst@....net>
Cc:     Shengyang Chen <shengyang.chen@...rfivetech.com>,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        thierry.reding@...il.com, neil.armstrong@...aro.org,
        conor+dt@...nel.org, keith.zhao@...rfivetech.com,
        tzimmermann@...e.de, krzysztof.kozlowski+dt@...aro.org,
        sam@...nborg.org, linux-kernel@...r.kernel.org, mripard@...nel.org,
        jack.zhu@...rfivetech.com, robh+dt@...nel.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        florian.fainelli@...adcom.com, quic_jesszhan@...cinc.com,
        changhuang.liang@...rfivetech.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 0/2] Add waveshare 7inch touchscreen panel support

On Fri, 24 Nov 2023 at 15:00, Stefan Wahren <wahrenst@....net> wrote:
>
> Hi Shengyang,
>
> [fix address of Emma]

Not merged to master yet, but Emma has stepped back from maintenance.
https://lists.freedesktop.org/archives/dri-devel/2023-October/428829.html
Dropped from the cc.

> 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.

Agreed.

The panel control being bound in with the Atmel control has no hook
for the EDT5x06 touch driver to hook in and keep the power to the
touch controller active. When the panel disable gets called, bye bye
touch overlay :-(

And I'm reading the driver change as more of a hack to get it to work
on your platform, not as adding support for the Waveshare panel
variant.
Waveshare deliberately cloned the behaviour of the Pi 7" panel in
order to make it work with the old Pi firmware drivers, so it
shouldn't need any significant changes. Where did the new timings come
from?

  Dave

> 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(-)
> >
>