Re: [PATCH v2 3/3] tps6507x-ts: add DT bindings description

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Fri, Mar 10, 2017 at 08:54:51PM +0100, Yegor Yefremov wrote:
> On Fri, Mar 10, 2017 at 7:00 PM, Dmitry Torokhov
> <dmitry.torokhov@gmail.com> wrote:
> > On Fri, Mar 10, 2017 at 12:11:08PM +0530, Sekhar Nori wrote:
> >> On Thursday 09 March 2017 11:25 PM, Dmitry Torokhov wrote:
> >> > On Thu, Mar 09, 2017 at 04:18:40PM +0100, Yegor Yefremov wrote:
> >> >> On Thu, Mar 9, 2017 at 3:49 PM, Rob Herring <robh@kernel.org> wrote:
> >> >>> On Thu, Mar 9, 2017 at 8:31 AM,  <yegorslists@googlemail.com> wrote:
> >> >>>> From: Yegor Yefremov <yegorslists@googlemail.com>
> >> >>>
> >> >>> This needs to go to DT list.
> >> >>
> >> >> Will do.
> >> >>
> >> >>>>
> >> >>>> Provide description for following properties:
> >> >>>>
> >> >>>> - ti,poll-period
> >> >>>> - ti,min-pressure
> >> >>>>
> >> >>>> Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
> >> >>>> ---
> >> >>>>  Documentation/devicetree/bindings/mfd/tps6507x.txt | 16 ++++++++++++++--
> >> >>>>  1 file changed, 14 insertions(+), 2 deletions(-)
> >> >>>>
> >> >>>> diff --git a/Documentation/devicetree/bindings/mfd/tps6507x.txt b/Documentation/devicetree/bindings/mfd/tps6507x.txt
> >> >>>> index 8fffa3c..8875662 100644
> >> >>>> --- a/Documentation/devicetree/bindings/mfd/tps6507x.txt
> >> >>>> +++ b/Documentation/devicetree/bindings/mfd/tps6507x.txt
> >> >>>> @@ -1,4 +1,8 @@
> >> >>>> -TPS6507x Power Management Integrated Circuit
> >> >>>> +TPS6507x Multifunctional Device.
> >> >>>> +
> >> >>>> +Features provided by TPS6507x:
> >> >>>> +        1. Power Management Integrated Circuit.
> >> >>>> +        2. Touch-Screen.
> >> >>>>
> >> >>>>  Required properties:
> >> >>>>  - compatible: "ti,tps6507x"
> >> >>>> @@ -30,6 +34,12 @@ Regulator Optional properties:
> >> >>>>                         1: If defdcdc pin of DCDC2/DCDC3 is driven HIGH.
> >> >>>>    If this property is not defined, it defaults to 0 (not enabled).
> >> >>>>
> >> >>>> +Touchscreen Optional properties:
> >> >>>> +- ti,poll-period: Time at which touch input is getting sampled in ms.
> >> >>>> +                 Default value: 30 ms.
> >> >>>
> >> >>> Isn't there a standard property for this?
> >> >>
> >> >> Such a value will be already used in [1]. I've looked at [2], but it
> >> >> doesn't have such a field.
> >> >>
> >> >> [1] Documentation/devicetree/bindings/input/touchscreen/tsc2007.txt
> >> >> [2] Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
> >> >
> >> > I think the bigger question (since we are adding this to DT I assume it
> >> > is not longer "toy" driver) can we convert it to a proper
> >> > interrupt-driven scheme? Polling for real shipping devices is not
> >> > efficient, I do not think we should even try to allow this mode in DTS
> >> > bindings (note that tsc2007 use is different: it allows to specify
> >> > sampling interval once touch is detected).
> >>
> >> Unfortunately, the only current user of tps6507x in kernel (da850-evm)
> >> does not have the touch interrupt connected to the processor. So if we
> >> dont support polled mode in when using device-tree, da850-evm.dts wont
> >> be able to use this driver.
> >
> > Do we care? Right now the driver is unusable for any practical
> > application I think as it burns CPU cycles by constantly polling the
> > touch controller.
> >
> > Yegor, your conversion to device tree: is it done because you have a
> > real product using this?
> 
> Yes. It is VS-860 device http://www.visionsystems.de/produkte/vs-860.html
> 
> It even seems to have interrupt pin connected. So we have to support both modes.

Well, I'd rather supported interrupt only. Polling is a toy mode.

Thanks.

-- 
Dmitry