On 2018-08-03 10:51, jacopo mondi wrote:
On Fri, Aug 03, 2018 at 10:40:02AM +0200, Peter Rosin wrote:
On 2018-08-03 10:11, jacopo mondi wrote:
Hi Peter!
On Fri, Aug 03, 2018 at 09:23:07AM +0200, Peter Rosin wrote:
With bus-type/bus-width properties in the endpoint nodes, the video- interface of the connection can be specified for cases where the heuristic fails to select the correct output mode. This can happen e.g. if not all RGB pins are routed on the PCB; the driver has no way of knowing this, and needs to be told explicitly.
This is critical for the devices that have the "conflicting output formats" issue (SAM9N12, SAM9X5, SAMA5D3), since the most significant RGB bits move around depending on the selected output mode. For devices that do not have the "conflicting output formats" issue (SAMA5D2, SAMA5D4), this is completely irrelevant.
Acked-by: Boris Brezillon boris.brezillon@bootlin.com Reviewed-by: Rob Herring robh@kernel.org Signed-off-by: Peter Rosin peda@axentia.se
.../devicetree/bindings/display/atmel/hlcdc-dc.txt | 26 ++++++++++++++++++++++ 1 file changed, 26 insertions(+)
diff --git a/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt b/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt index 82f2acb3d374..9de434a8f523 100644 --- a/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt +++ b/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt @@ -15,6 +15,14 @@ Required children nodes: to external devices using the OF graph reprensentation (see ../graph.txt). At least one port node is required.
+Optional properties in grandchild nodes:
- Any endpoint grandchild node may specify a desired video interface
- according to ../../media/video-interfaces.txt, specifically
- bus-type: must be <0>.
Is there any value in specifying this, if it has a fixed value to "autodetect"? I understand it's optional, so if nobody else objects, feels free to keep it there.
That's just how media/video-interfaces.txt works.
bus-type 0 means that other properties describe the bus type. In this case bus-width is specified, so that means a parallel bus. But bus-width has no meaning (or may not have) if bus-type is non-zero. But checking that bus-type for zero in the code seemed like overkill to me since the driver already knows that it is a parallel bus...
Yeah, I felt like pointing that out since you're not cheking for its value, and that property is only used by v4l2-fwnode to handle some not-that-used-anymore bus as CCP2 is.
TL;DR I'd like to keep it.
Fine with me then.
- bus-width: recognized values are <12>, <16>, <18> and <24>, and
- override any output mode selection heuristic, forcing "rgb444",
- "rgb565", "rgb666" and "rgb888" respectively.
Example:
hlcdc: hlcdc@f0030000 { @@ -50,3 +58,21 @@ Example: #pwm-cells = <3>; }; };
Two blank lines here.
+Example 2: With a video interface override to force rgb565; as above +but with these changes/additions:
- &hlcdc {
hlcdc-display-controller {pinctrl-names = "default";pinctrl-0 = <&pinctrl_lcd_base &pinctrl_lcd_rgb565>;port@0 {The node has a unit address specified, you're missing a reg = <0> property (no big deal, it's an example, but the other one has it)
hlcdc_panel_output: endpoint@0 {Missing reg here too.
I'll fix those (I think they appeared for the original example after I wrote the patch).
Ok, then please consider also describing the port@0 node cell sizes too since it has a child endpoint node.
Ok, I have now figured out why this was as it were, and I no longer agree with adding the extra properties. The whole of example 2 is inside a reference (using the &hlcdc notation) to the hlcdc node in example 1, and therefore these "missing" properties are not missing. I think they are just clutter that hides what is really needed/different between example 1 and 2, and apparently Boris and Rob agreed when they acked/reviewed. The description of example 2 also clearly states that example 2 is changes and additions on top of example 1. So, I plan to have this in the next iteration:
&hlcdc { hlcdc-display-controller { pinctrl-names = "default"; pinctrl-0 = <&pinctrl_lcd_base &pinctrl_lcd_rgb565>;
port@0 { hlcdc_panel_output: endpoint@0 { bus-width = <16>; }; }; }; };
Jacopo, please let me know if you want me to keep your review tag anyway...
Cheers, Peter
Minors apart:
...because I interpret this to mean that I could add your tag if I made the changes you suggested. Or did it mean that I could add your tag regardless because the issues were minor?
Cheers, Peter
Reviewed-by: Jacopo Mondi jacopo+renesas@jmondi.org
Thanks j
bus-type = <0>;bus-width = <16>;};};};- };
-- 2.11.0