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

From: Neil Armstrong
Date: Fri Jan 12 2024 - 04:14:51 EST


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@xxxxxxxxxxxxx> 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