linux-kernel - Re: [PATCH v2 2/4] drm/panel: Add driver for DJN HX83112A LCD panel

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Message-ID: <CACRpkdZQbVXfBa70nhDOqfWPbsh-6DgX-uvZOxr19pzMmF2giQ@mail.gmail.com>
Date: Thu, 11 Jan 2024 20:05:04 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Luca Weiss <luca.weiss@...rphone.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Sam Ravnborg <sam@...nborg.org>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Andy Gross <agross@...nel.org>, devicetree@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, ~postmarketos/upstreaming@...ts.sr.ht, 
	phone-devel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] drm/panel: Add driver for DJN HX83112A LCD panel

On Thu, Jan 11, 2024 at 4:28 PM Luca Weiss <luca.weiss@...rphone.com> wrote:

> In some internal documentation it says "LCD Driver IC" "HX83112A" and I
> don't see any reference to Truly 5P65 anywhere.

In the Android directory I pointed to I see this file:
HX83112_Android_Driver/Truly_5p65_module_fw/UpdateFW.bat

(Notice the 5p65 fw dir is *inside* the HX82112 dir)

And in that file:
adb push TRULY_5P65_1080_2160_HX83112A_D01C01.bin
/system/etc/firmware/Himax_firmware.bin

Clearly indicating that they are pushing a Truly 5P65 firmware into
the Himax display firmware directory.

To be fair, that is the driver for the touchscreen part of HX83112A,
but ... Truly is a well known manufacturer of display controllers?

But... given that you have a @fairphone.com mal address and
a working relationship with them, can't you just ask?

> On their website they have this sentence:

All OEMs want to look like everything is their own product. It is
business as usual.

Further on the same note since I guess you have a datasheet)
please bring in #defines for the commands (the first byte in the
write sequences, for examples:

+       mipi_dsi_dcs_write_seq(dsi, 0xbd, 0x02);
+       mipi_dsi_dcs_write_seq(dsi, 0xd8,
+                              0xaa, 0xff, 0xff, 0xff, 0xff, 0xff, 0xaa, 0xff,
+                              0xff, 0xff, 0xff, 0xff);
+       mipi_dsi_dcs_write_seq(dsi, 0xbd, 0x03);

Clearly 0xbd is HX83112_CMD_SETREGBANK?
(This is easily spotted from the similar structure in the
existing panel-himax-hx8394.c.) So please add #defines
for all commands you know, especially if you have a datasheet
because we reviewers don't have them and "it's just magic
bytes" isn't very compelling. It adds a lot to understanding.

I strongly suspect other Himax displays such as HX8394 to
be using a Truly controller as well, hence the similarities.

In a datasheet for their TFT800480-84-V1-E display controller
Truly kept the init sequence name of void LCD_INIT_HX8290(void)
for example.

Yours,
Linus Walleij