Date: Fri, 12 Jan 2024 10:00:17 +0100
From: "Luca Weiss" <luca.weiss@...rphone.com>
To: "Linus Walleij" <linus.walleij@...aro.org>
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 8:05 PM CET, Linus Walleij wrote:
> 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.

I can't tell you anything there that I don't know, sorry.

>
> 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.

Right, the register names seem to match more or less the ones from that
driver, plus some new ones and some differently named ones. Will send a
v3 with that.

>
> 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.

In that datasheet (assuming I'm looking at the same one?) it says
"Driver IC" "HX8290-A[...]" so there the display driver is manufactured
by Himax and not Truly to my understanding. Truly is assembling together
Driver + all the other parts that go into an LCD.

For the panel used on Fairphone 4 that part is done by the company DJN.

Regards
Luca

>
> Yours,
> Linus Walleij

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