linux-kernel - Re: [PATCH v2 8/8] DT:omap3+ads7846: use new common touchscreen bindings

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Date:	Mon, 16 Nov 2015 16:31:24 +0100
From:	"H. Nikolaus Schaller" <hns@...delico.com>
To:	Grazvydas Ignotas <notasas@...il.com>
Cc:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Benoît Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Hans Verkuil <hans.verkuil@...co.com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Sebastian Reichel <sre@...nel.org>,
	Haibo Chen <haibo.chen@...escale.com>,
	Andrey Gelman <andrey.gelman@...pulab.co.il>,
	Igor Grinberg <grinberg@...pulab.co.il>,
	Aaron Sierra <asierra@...-inc.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	devicetree@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	gta04-owner@...delico.com, linux-input@...r.kernel.org
Subject: Re: [PATCH v2 8/8] DT:omap3+ads7846: use new common touchscreen bindings

HI,

Am 16.11.2015 um 15:37 schrieb Grazvydas Ignotas <notasas@...il.com>:

> Hi,
> 
> On Fri, Nov 13, 2015 at 10:35 PM, H. Nikolaus Schaller
> <hns@...delico.com> wrote:
>> The standard touch screen bindings [1] replace the private ti,swap-xy
>> with touchscreen-swaped-x-y. And for the Openpandora we use
>> touchscreen-size etc. to match the LCD screen size.
>> 
>> [1]: Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
>> 
>> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
>> ---
>> arch/arm/boot/dts/omap3-lilly-a83x.dtsi              |  2 +-
>> arch/arm/boot/dts/omap3-pandora-common.dtsi          | 17 +++++++++++++----
>> arch/arm/boot/dts/omap3-panel-sharp-ls037v7dw01.dtsi |  2 +-
>> 3 files changed, 15 insertions(+), 6 deletions(-)
>> 
>> diff --git a/arch/arm/boot/dts/omap3-lilly-a83x.dtsi b/arch/arm/boot/dts/omap3-lilly-a83x.dtsi
>> index d0dd036..01dae66 100644
>> --- a/arch/arm/boot/dts/omap3-lilly-a83x.dtsi
>> +++ b/arch/arm/boot/dts/omap3-lilly-a83x.dtsi
>> @@ -325,7 +325,7 @@
>>                ti,y-max = /bits/ 16 <3600>;
>>                ti,x-plate-ohms = /bits/ 16 <80>;
>>                ti,pressure-max = /bits/ 16 <255>;
>> -               ti,swap-xy;
>> +               touchscreen-swapped-x-y;
>> 
>>                linux,wakeup;
>>        };
>> diff --git a/arch/arm/boot/dts/omap3-pandora-common.dtsi b/arch/arm/boot/dts/omap3-pandora-common.dtsi
>> index f672a04..9497cc6 100644
>> --- a/arch/arm/boot/dts/omap3-pandora-common.dtsi
>> +++ b/arch/arm/boot/dts/omap3-pandora-common.dtsi
>> @@ -696,10 +696,19 @@
>>                pendown-gpio = <&gpio3 30 0>;
>>                vcc-supply = <&vaux4>;
>> 
>> -               ti,x-min = /bits/ 16 <0>;
>> -               ti,x-max = /bits/ 16 <8000>;
>> -               ti,y-min = /bits/ 16 <0>;
>> -               ti,y-max = /bits/ 16 <4800>;
>> +               touchscreen-size-x = <800>;
>> +               touchscreen-size-y = <480>;
>> +               touchscreen-max-pressure = <1000>;
>> +               touchscreen-fuzz-x = <16>;
>> +               touchscreen-fuzz-y = <16>;
>> +               touchscreen-fuzz-pressure = <10>;
>> +               touchscreen-inverted-x;
>> +               touchscreen-inverted-y;
>> +
>> +               ti,x-min = /bits/ 16 <160>;
>> +               ti,x-max = /bits/ 16 <3900>;
>> +               ti,y-min = /bits/ 16 <220>;
>> +               ti,y-max = /bits/ 16 <3750>;
> 
> I'm not sure this is a good idea, there have been at least 3 different
> batches of LCDs which slightly different touchscreens attached, with
> such thresholds we might end up with unreachable touchscreen points on
> some units. If I understand right, calibration won't help if for some
> screen locations ADC reading goes below/above these min/max thresholds
> on some specific units? If so there should probably be at least 10%
> margin in either case to make calibration useful.

Ok, then someone owning all variants should test and we should use the
min/max values we find. I.e. the touch with the biggest ADC value range.
All others have smaller screens which can be calibrated in user space.
But 10% is good enough to boot and start manual calibration.

Alternatively, we can set them to 0 and 4095 (or remove them to use defaults).

BR and thanks,
Nikolaus

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