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

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Date: Fri, 12 Jan 2024 10:14:30 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Luca Weiss <luca.weiss@...rphone.com>,
 Linus Walleij <linus.walleij@...aro.org>
Cc: 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 12/01/2024 10:00, Luca Weiss wrote:
> 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.

Looking at the discussion, this seems to confirm the Display+Touch IC is HX83112A,
and Truly is the panel manufacturer and all assembled by DJN, so IMHO the initial driver is right.

Perhaps the compatible should be djn,hx83112a-truly-5p65 to reflect that ?

Neil

> 
> Regards
> Luca
> 
>>
>> Yours,
>> Linus Walleij
>