Hi,
On 18-05-2021 01:51, Doug Anderson wrote:
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
Thank you, for all your suggestions.
I have posted the new patch series (v4) on top of the above series. Please check: https://lore.kernel.org/dri-devel/1621927831-29471-1-git-send-email-rajeevny...
Thanks, Rajeev