Re: [PATCH v3 3/5] drm: panel: Add Xingbangda XBD599 panel (ST7703 controller)

From: Linus Walleij <linus.walleij@linaro.org>
To: Ondrej Jirman <megous@megous.com>
Cc: linux-sunxi <linux-sunxi@googlegroups.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Sam Ravnborg <sam@ravnborg.org>, David Airlie <airlied@linux.ie>,
	Daniel Vetter <daniel@ffwll.ch>, Rob Herring <robh+dt@kernel.org>,
	Maxime Ripard <mripard@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
	Icenowy Zheng <icenowy@aosc.io>,
	"open list:DRM PANEL DRIVERS" <dri-devel@lists.freedesktop.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Samuel Holland <samuel@sholland.org>,
	Martijn Braam <martijn@brixit.nl>, Luca Weiss <luca@z3ntu.xyz>,
	Bhushan Shah <bshah@kde.org>
Subject: Re: [PATCH v3 3/5] drm: panel: Add Xingbangda XBD599 panel (ST7703 controller)
Date: Tue, 26 May 2020 13:32:25 +0200	[thread overview]
Message-ID: <CACRpkdZpiQ7E_v-Gfk6vFcUEiMazvixYaL0ksKeP=Tq3O6Fh=Q@mail.gmail.com> (raw)
In-Reply-To: <20200513212451.1919013-4-megous@megous.com>

Hi Ondrej,

I see you took over this driver submission from
Icenowy.

On Wed, May 13, 2020 at 11:24 PM Ondrej Jirman <megous@megous.com> wrote:

> From: Icenowy Zheng <icenowy@aosc.io>
>
> Xingbangda XBD599 is a 5.99" 720x1440 MIPI-DSI IPS LCD panel made by
> Xingbangda, which is used on PinePhone final assembled phones.
>
> It is based on Sitronix ST7703 LCD controller.
>
> Add support for it.
>
> Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
> Signed-off-by: Ondrej Jirman <megous@megous.com>

(...)
>  create mode 100644 drivers/gpu/drm/panel/panel-sitronix-st7703.c

Nice!

> +       /*
> +        * Init sequence was supplied by the panel vendor.
> +        */
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETEXTC,
> +                         0xF1, 0x12, 0x83);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETMIPI,
> +                         0x33, 0x81, 0x05, 0xF9, 0x0E, 0x0E, 0x20, 0x00,
> +                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x44, 0x25,
> +                         0x00, 0x91, 0x0a, 0x00, 0x00, 0x02, 0x4F, 0x11,
> +                         0x00, 0x00, 0x37);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETPOWER_EXT,
> +                         0x25, 0x22, 0x20, 0x03);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETRGBIF,
> +                         0x10, 0x10, 0x05, 0x05, 0x03, 0xFF, 0x00, 0x00,
> +                         0x00, 0x00);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETSCR,
> +                         0x73, 0x73, 0x50, 0x50, 0x00, 0xC0, 0x08, 0x70,
> +                         0x00);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETVDC, 0x4E);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETPANEL, 0x0B);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETCYC, 0x80);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETDISP, 0xF0, 0x12, 0xF0);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETEQ,
> +                         0x00, 0x00, 0x0B, 0x0B, 0x10, 0x10, 0x00, 0x00,
> +                         0x00, 0x00, 0xFF, 0x00, 0xC0, 0x10);
> +       dsi_dcs_write_seq(dsi, 0xC6, 0x01, 0x00, 0xFF, 0xFF, 0x00);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETPOWER,
> +                         0x74, 0x00, 0x32, 0x32, 0x77, 0xF1, 0xFF, 0xFF,
> +                         0xCC, 0xCC, 0x77, 0x77);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETBGP, 0x07, 0x07);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETVCOM, 0x2C, 0x2C);
> +       dsi_dcs_write_seq(dsi, 0xBF, 0x02, 0x11, 0x00);
> +
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETGIP1,
> +                         0x82, 0x10, 0x06, 0x05, 0xA2, 0x0A, 0xA5, 0x12,
> +                         0x31, 0x23, 0x37, 0x83, 0x04, 0xBC, 0x27, 0x38,
> +                         0x0C, 0x00, 0x03, 0x00, 0x00, 0x00, 0x0C, 0x00,
> +                         0x03, 0x00, 0x00, 0x00, 0x75, 0x75, 0x31, 0x88,
> +                         0x88, 0x88, 0x88, 0x88, 0x88, 0x13, 0x88, 0x64,
> +                         0x64, 0x20, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88,
> +                         0x02, 0x88, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
> +                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETGIP2,
> +                         0x02, 0x21, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
> +                         0x00, 0x00, 0x00, 0x00, 0x02, 0x46, 0x02, 0x88,
> +                         0x88, 0x88, 0x88, 0x88, 0x88, 0x64, 0x88, 0x13,
> +                         0x57, 0x13, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88,
> +                         0x75, 0x88, 0x23, 0x14, 0x00, 0x00, 0x02, 0x00,
> +                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
> +                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x0A,
> +                         0xA5, 0x00, 0x00, 0x00, 0x00);
> +       dsi_dcs_write_seq(dsi, ST7703_CMD_SETGAMMA,
> +                         0x00, 0x09, 0x0D, 0x23, 0x27, 0x3C, 0x41, 0x35,
> +                         0x07, 0x0D, 0x0E, 0x12, 0x13, 0x10, 0x12, 0x12,
> +                         0x18, 0x00, 0x09, 0x0D, 0x23, 0x27, 0x3C, 0x41,
> +                         0x35, 0x07, 0x0D, 0x0E, 0x12, 0x13, 0x10, 0x12,
> +                         0x12, 0x18);
> +       msleep(20);

This stuff is really hard or impossible to understand without the
datasheet.

In my previous review I wrote:

It appears that the Himax HX8363 is using the same display controller
if you look at the datasheet:
http://www.datasheet-pdf.com/PDF/HX8369-A-Datasheet-Himax-729024
There you find an explanation to some of the commands.

That means, try to get rid of as much of the magic bytes as you can
and use proper #defines. I know it takes some work but the result
is so much more useful and readable.

Further I wrote:

You should definately insert code to read the MTP bytes:
0xDA manufacturer
0xDB driver version
0xDC LCD module/driver
And print these, se e.g. my newly added NT35510 driver or
the Sony ACX424AKP driver.

So please do that.

Yours,
Linus Walleij