| Message ID | 20180803101124.4622-3-peda@axentia.se (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/atmel-hlcdc: bus-width override support | expand |
On 2018-08-03 12:32, Sakari Ailus wrote: > Hi Peter, > > Thanks for cc'ing me. You're welcome, but Laurent is the one to "blame" for hooking you up... :-) > On Fri, Aug 03, 2018 at 12:11:23PM +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> >> Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org> >> Signed-off-by: Peter Rosin <peda@axentia.se> >> --- >> .../devicetree/bindings/display/atmel/hlcdc-dc.txt | 30 ++++++++++++++++++++++ >> 1 file changed, 30 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt b/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt >> index 82f2acb3d374..10e8707d1443 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>. > > bus-type won't tell anything in this case, you could simply drop it. If > your hardware only supports parallel or Bt.656 bus then the code parsing > the properties can (and should) know the bus type as well. > > Looking at your implementation, bus-type is not being used. This supports > the suggestion. I only added the "bus-type = <0>;" in order to disallow any other value for the bus-type to make it clear that any non-zero value would be a bug in the device-tree and not in the driver... > The V4L2 implementation is about to change as well and there's a bit of > discussion ongoing related to the bus-type property: > > <URL:https://www.spinics.net/lists/linux-media/msg137980.html> > <URL:https://www.spinics.net/lists/linux-media/msg137979.html> ...but I can certainly drop "bus-type = <0>;" from the binding if it is going away anyway. However, I wonder why it's ok to silently drop the autodetect meaning of zero? What about old device-trees that do have that zero there? Are those suddenly not conforming? Wouldn't a deprecation notice be better so that old existing device-trees can be parsed/understood even when using modern bindings documentation? Cheers, Peter > >> + - 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 +58,25 @@ Example: >> #pwm-cells = <3>; >> }; >> }; >> + >> +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 { >> + #address-cells = <1>; >> + #size-cells = <0>; >> + reg = <0>; >> + >> + hlcdc_panel_output: endpoint@0 { >> + reg = <0>; >> + bus-type = <0>; >> + bus-width = <16>; >> + }; >> + }; >> + }; >> + }; >
diff --git a/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt b/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt index 82f2acb3d374..10e8707d1443 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>. + - 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 +58,25 @@ Example: #pwm-cells = <3>; }; }; + +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 { + #address-cells = <1>; + #size-cells = <0>; + reg = <0>; + + hlcdc_panel_output: endpoint@0 { + reg = <0>; + bus-type = <0>; + bus-width = <16>; + }; + }; + }; + };