Messages in this thread | | | Subject | Re: [PATCH v3 3/6] dt-bindings: add binding for Sitronix ST7586 display panels | From | David Lechner <> | Date | Sat, 5 Aug 2017 11:13:47 -0500 |
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On 08/04/2017 02:39 PM, Laurent Pinchart wrote: > Hi David, > > On Friday 04 Aug 2017 10:51:37 David Lechner wrote: >> On 08/04/2017 09:54 AM, Laurent Pinchart wrote: >>> On Thursday 03 Aug 2017 17:33:47 David Lechner wrote: >>>> This adds a new binding for Sitronix ST7586 display panels. >>>> >>>> Using lego as the vendor prefix in the compatible string because the >>>> display panel I am working with is an integral part of the LEGO >>>> MINDSTORMS EV3. >>>> >>>> Signed-off-by: David Lechner <david@lechnology.com> >>>> --- >>>> >>>> .../bindings/display/sitronix,st7586.txt | 26 >>>> +++++++++++++++++++ >>>> 1 file changed, 26 insertions(+) >>>> create mode 100644 >>>> >>>> Documentation/devicetree/bindings/display/sitronix,st7586.txt >>>> >>>> diff --git >>>> a/Documentation/devicetree/bindings/display/sitronix,st7586.txt >>>> b/Documentation/devicetree/bindings/display/sitronix,st7586.txt new file >>>> mode 100644 >>>> index 0000000..dfb0b7b >>>> --- /dev/null >>>> +++ b/Documentation/devicetree/bindings/display/sitronix,st7586.txt >>>> @@ -0,0 +1,26 @@ >>>> +Sitronix ST7586 display panel >>>> + >>>> +Required properties: >>>> +- compatible: "lego,ev3-lcd". >>>> + >>>> +The node for this driver must be a child node of a SPI controller, hence >>>> +all mandatory properties described in ../spi/spi-bus.txt must be >>>> specified. + >>>> +Optional properties: >>>> +- dc-gpios: D/C pin. The presence/absence of this GPIO determines >>>> + the panel interface operation mode (IF[3:1] pins): >>>> + - present: IF=011 4-wire 8-bit data serial interface >>>> + - absent: IF=010 3-wire 9-bit data serial interface >>> >>> How does this work ? Do you have a single GPIO on your system connected to >>> IF[1], with IF[3:2] hardwired to 01 ? >> >> LEGO has not made the internals of the display publicly available, so I >> cannot say for sure. But I assume that IF[3:1] is hardwired to 011. This >> causes pin D1 to assigned to the signal A0, which is what we are calling >> the dc gpio here. >> >> If IF[3:1] were hardwired to 010, then pin D1 would be not not used and >> there would be no A0 signal. >> >> So, basically, we can infer the state of IF[3:1] by the fact that we >> have a dc pin or not. > > OK, now I understand what you mean. Maybe you should phrase it a bit > differently to make it clearer ? How about > > dc-gpios: Specified or the GPIO connected to the panel's D/C pin (also called > A0). The property is required when the panel operates in 4-wire mode (IF[3:1] > = 011) and prohibited when the panel operates in 3-wire mode (IF[3:1] = 010).
Yes, this is more clear. Thank you for the suggestion.
> > By the way, if the signal is named A0, why don't you call the property a0- > gpios ?
I consider "dc-gpios" to be a generic name since it is used by many different panels. But I would be OK with calling it "a0-gpios" as well. It will just require more explanation that this is the A0 *signal* and not the A0 *pin*. The actual pin used is labeled *D1* on the controller.
On the other hand, it is labeled as A0 on LEGO's schematic, so perhaps a0 is better.
> >>>> +- reset-gpios: Reset pin >>>> +- power-supply: A regulator node for the supply voltage. >>>> +- backlight: phandle of the backlight device attached to the panel >>>> +- rotation: panel rotation in degrees counter clockwise > (0,90,180,270) >>> >>> Please use the OF graph DT bindings (a.k.a. ports) to describe the >>> connection between the panel and its source. >> >> I am afraid that I do not understand this request. What would the source >> of the panel be? There is nothing like a SoC LCD controller that is >> driving this panel. > > My bad, I should have read the panel datasheet before replying :-S Please > ignore this comment. > >>>> +Example: >>>> + display@0{ >>>> + compatible = "lego,ev3-lcd"; >>>> + reg = <0>; >>>> + spi-max-frequency = <10000000>; >>>> + dc-gpios = <&gpio 43 GPIO_ACTIVE_HIGH>; >>>> + reset-gpios = <&gpio 80 GPIO_ACTIVE_HIGH>; >>>> + }; >
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