| 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 |
Hi Peter, Thanks for cc'ing me. 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. 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> > + - 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>; > + }; > + }; > + }; > + };
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>; + }; + }; + }; + };