Hi,
On Tue, May 11, 2021 at 4:17 PM Doug Anderson dianders@chromium.org wrote:
Hi,
On Tue, May 11, 2021 at 11:12 AM rajeevny@codeaurora.org wrote:
On 01-05-2021 03:08, Doug Anderson wrote:
Hi,
On Fri, Apr 30, 2021 at 8:10 AM rajeevny@codeaurora.org wrote:
On 30-04-2021 02:33, Doug Anderson wrote:
Hi,
On Thu, Apr 29, 2021 at 11:04 AM Rob Herring robh@kernel.org wrote:
On Mon, Apr 26, 2021 at 11:29:15AM +0530, Rajeev Nandan wrote: > Add bindings for DisplayPort aux backlight driver. > > Changes in v2: > - New > > Signed-off-by: Rajeev Nandan rajeevny@codeaurora.org > --- > .../bindings/leds/backlight/dp-aux-backlight.yaml | 49 ++++++++++++++++++++++ > 1 file changed, 49 insertions(+) > create mode 100644 Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml > > diff --git a/Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml > new file mode 100644 > index 00000000..0fa8bf0 > --- /dev/null > +++ b/Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml > @@ -0,0 +1,49 @@ > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/leds/backlight/dp-aux-backlight.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: DisplayPort aux backlight driver bindings > + > +maintainers: > + - Rajeev Nandan rajeevny@codeaurora.org > + > +description: > + Backlight driver to control the brightness over DisplayPort aux channel. > + > +allOf: > + - $ref: common.yaml# > + > +properties: > + compatible: > + const: dp-aux-backlight > + > + ddc-i2c-bus: > + $ref: /schemas/types.yaml#/definitions/phandle > + description: > + A phandle to the system I2C controller connected to the DDC bus used > + for the DisplayPort AUX channel. > + > + enable-gpios: > + maxItems: 1 > + description: GPIO specifier for backlight enable pin. > + > + max-brightness: true > + > +required: > + - compatible > + - ddc-i2c-bus > + > +additionalProperties: false > + > +examples: > + - | > + backlight { > + compatible = "dp-aux-backlight"; > + ddc-i2c-bus = <&sn65dsi86_bridge>; > + enable-gpios = <&tlmm 12 GPIO_ACTIVE_HIGH>;
So the DDC bus is connected to a backlight and also a panel? This binding is not reflecting the h/w, but rather what you want for some driver.
There's only one thing here and that's an eDP panel which supports backlight control via DP aux channel. You can figure all that out from the panel's compatible and/or reading the EDID.
You might also be interested in this thread:
https://lore.kernel.org/lkml/YIKsDtjcIHGNvW0u@orome.fritz.box/
I think Rajeev needs to rework everything anyway as per:
https://lore.kernel.org/r/87zgxl5qar.fsf@intel.com
...but you're right that it makes sense not to model the backlight as a separate node in the device tree. The panel driver can handle setting up the backlight.
-Doug
It was not a good idea to create a separate backlight driver and use ddc-i2c-bus to get access to DP aux. I am working to move the code to the panel driver and to utilize the new DRM helper functions (drm_edp_backlight_*) Lyude has added [1].
To use these helper functions, the panel driver should have access to the "struct drm_dp_aux *". The simple-panel has a "ddc-i2c-bus" property to give the panel access to the DDC bus and is currently being used to get the EDID from the panel. Can I use the same ddc bus i2c_adapter to get the "struct drm_dp_aux *"?
As per the suggestion [2], I get the "struct drm_dp_aux *" from the i2c_adapter of ddc bus (maybe I didn't understand the suggestion correctly), and, it turned out, the way I have implemented is not the right way [3]. So, I am afraid to use the same method in the panel driver.
[1] https://lore.kernel.org/dri-devel/871rb5bcf9.fsf@intel.com/ [2] https://www.spinics.net/lists/dri-devel/msg295429.html [3] https://lore.kernel.org/dri-devel/20210426111116.4lc3ekxjugjr3oho@maple.lan/
So it's definitely up to maintainers, not me. ...but I guess I would have expected something like a new property called "ddc-aux-bus". Then you'd have to create a new API call called something like "of_find_ddc_aux_adapter_by_node()" that would allow you to find it.
To implement the first suggestion, I can think of the following way to get the "struct drm_dp_aux" in the panel_simple_probe function:
- Create a new panel-simple DT property "ddc-aux-bus", a phandle to the
platform device that implements the AUX channel.
- Create a global list of drm_dp_aux in drm_dp_helper.c. Initialize list
head in drm_dp_aux_init(), add the drm_dp_aux onto the list in drm_dp_aux_register(). Similarly, remove the drm_dp_aux from list in drm_dp_aux_unregister().
- Create a new function of_drm_find_dp_aux_by_node() to get the expected
drm_dp_aux from this global list.
Please let me know your views on this implementation.
BTW: a bunch of discussion today on IRC:
https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&highli...
To finish adding breadcrumbs to those playing at home, v7 of my patch series should get the AUX channel to the panel device:
https://lore.kernel.org/r/20210517200907.1459182-1-dianders@chromium.org/
Assuming that people don't hate that solution it may be a good things for you to build your patches atop. :-)
-Doug