Hi Noralf,
Le dim. 14 juin 2020 à 18:36, Noralf Trønnes <noralf@xxxxxxxxxxx> a
écrit :
Den 07.06.2020 15.38, skrev Paul Cercueil:
Hi,
Here's a follow-up on the previous discussion about the current
state of
DSI/DBI panel drivers, TinyDRM, and the need of a cleanup.
This patchset introduces the following:
* It slightly tweaks the MIPI DSI code so that it supports MIPI DBI
over
various buses. This patch has been tested with a non-upstream DRM
panel driver for a ILI9331 DBI/8080 panel, written with the DSI
framework (and doesn't include <drm/drm_mipi_dbi.h>), and
non-upstream
DSI/DBI host driver for the Ingenic SoCs.
* A SPI DBI host driver, using the current MIPI DSI framework. It
allows
MIPI DSI/DBI drivers to be written with the DSI framework, even if
they are connected over SPI, instead of registering as SPI device
drivers. Since most of these panels can be connected over various
buses, it permits to reuse the same driver independently of the
bus
used.
* A TinyDRM driver for DSI/DBI panels, once again independent of
the bus
used; the only dependency (currently) being that the panel must
understand DCS commands.
* A DRM panel driver to test the stack. This driver controls Ilitek
ILI9341 based DBI panels, like the Adafruit YX240QV29-T 320x240
2.4"
TFT LCD panel. This panel was converted from
drivers/gpu/drm/tiny/ili9341.c.
I would like to emphasize that while it has been compile-tested, I
did
not test it with real hardware since I do not have any DBI panel
connected over SPI. I did runtime-test the code, just without any
panel
connected.
Another thing to note, is that it does not break Device Tree ABI.
The
display node stays the same:
display@0 {
compatible = "adafruit,yx240qv29", "ilitek,ili9341";
reg = <0>;
spi-max-frequency = <32000000>;
dc-gpios = <&gpio0 9 GPIO_ACTIVE_HIGH>;
reset-gpios = <&gpio0 8 GPIO_ACTIVE_HIGH>;
rotation = <270>;
backlight = <&backlight>;
};
The reason it works, is that the "adafruit,yx240qv29" device is
probed
on the SPI bus, so it will match with the SPI/DBI host driver. This
will
in turn register the very same node with the DSI bus, and the
ILI9341
DRM panel driver will probe. The driver will detect that no
controller
is linked to the panel, and eventually register the DBI/DSI TinyDRM
driver.
I can't stress it enough that this is a RFC, so it still has very
rough
edges.
I don't know bridge and dsi drivers so I can't comment on that, but
one
thing I didn't like is that the DT compatible string has to be added
to
2 different modules.
That's a minimal drawback for a perfectly architectured design ;)
As an example, a MI0283QT panel (ILI9341) supports these interface
options:
1. SPI
Panel setup/control and framebuffer upload over SPI
2. SPI + DPI
Panel setup/control over SPI, framebuffer scanout over DPI
3. Parallel bus
Panel setup/control and framebuffer upload over parallel bus
My suggestion is to have one panel driver module that can support all
of
these like this:
For 1. and 2. a SPI driver is registered and if I understand your
example correctly of_graph_get_port_by_id() can be used during probe
to
distinguish between the 2 options and register a full DRM driver for
1.
and add a DRM panel for 2.
For 3. a DSI driver is registered (adapted for DBI use like you're
suggesting).
That means basically having two entry points per DBI driver, one as DSI
device and one as SPI device, the latter doing the job of the current
DBI-SPI bridge. I think i would be cleaner to just have duplicated
strings with the DBI-SPI bridge.
Cheers,
-Paul
Note that the interface part of the controller initialization will
differ between these, the panel side init will be the same I assume.
Noralf.
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
