linux-kernel - Re: [PATCH v2 2/4] dt-bindings: Add jdi lt070me05000 panel bindings

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Date:	Fri, 22 Apr 2016 13:59:13 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Vinay Simha <simhavcs@...il.com>
Cc:	Rob Herring <robh@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	"Sumit.semwal" <sumit.semwal@...aro.org>,
	John Stultz <john.stultz@...aro.org>,
	Archit Taneja <archit.taneja@...il.com>
Subject: Re: [PATCH v2 2/4] dt-bindings: Add jdi lt070me05000 panel bindings

On Fri, Apr 22, 2016 at 12:25:52PM +0530, Vinay Simha wrote:
> On Thu, Apr 21, 2016 at 9:15 PM, Rob Herring <robh@...nel.org> wrote:
> > On Wed, Apr 20, 2016 at 03:02:31PM +0530, Vinay Simha BN wrote:
> >> Add documentation for lt070me05000 panel
> >>
> >> Signed-off-by: Vinay Simha BN <simhavcs@...il.com>
> >> ---
> >>  .../bindings/display/panel/jdi,lt070me05000.txt    | 43 ++++++++++++++++++++++
> >>  1 file changed, 43 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/display/panel/jdi,lt070me05000.txt
> >>
> >> diff --git a/Documentation/devicetree/bindings/display/panel/jdi,lt070me05000.txt b/Documentation/devicetree/bindings/display/panel/jdi,lt070me05000.txt
> >> new file mode 100644
> >> index 0000000..ffe0550
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/display/panel/jdi,lt070me05000.txt
> >> @@ -0,0 +1,43 @@
> >> +JDI model LT070ME05000 1200x1920 7" DSI Panel
> >> +
> >> +Required properties:
> >> +- compatible: should be "jdi,lt070me05000"
> >> +- power-supply: phandle of the regulator that provides the supply voltage
> >> +  IOVCC , power supply for LCM (1.8V)
> >> +- vddp-supply: phandle of the regulator that provides the supply voltage
> >> +  Power IC supply (3-5V)
> >> +- dcdc_en-supply: phandle of the regulator that provides the supply voltage
> >> +  Power IC supply enable, High active
> >> +- reset-gpio: phandle of gpio for reset line
> >> +  This should be 8mA, gpio can be configured using mux and pinctrl.
> >> +  XRES, Reset, Low active
> >> +- enable-gpio: phandle of gpio for enable line
> >> +  LED_EN, LED backlight enable, High active
> >
> > These should all be -gpios instead.
> will implement in v3
> >
> >> +- vcc-gpio: phandle of regulator/gpio that provides the supply voltage
> >> +  VDD, LED power supply (3-5V)
> >
> > Is it a regulator or gpio?
> >
> VDD is LED power supply, but in nexus 7 2nd gen they are using gpio 23
> instead of regulator.
> if we use vcc-supply, not sure we can give the gpio device tree entry
> to it in nexus 7 dts. Any inputs ?

You can model it as a fixed regulator that's enabled by a GPIO. See:

	Documentation/devicetree/bindings/regulator/fixed-regulator.txt

> >> +
> >> +Optional properties:
> >> +- pwm-gpio: phandle of gpio/pwm
> >
> > This should use the PWM binding. It may not be a GPIO on some hosts.
> 
> pwm-gpio will go to the backlight (pwm). right now it is not used
> since pwm pm8921 upstream driver is not yet implemented. Shall i
> remove this pwm-gpio now and the backlight property when pwm pm8921 is
> implemented?

This suggests to me that you don't have a good idea yet what the final
binding would need to look like, so it might be better to get all the
dependencies in place first so that the binding can be validated to work
properly.

Thierry

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