linux-kernel - RE: [PATCH v3 3/5] Input: goodix

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Date:	Thu, 30 Jul 2015 11:32:11 +0000
From:	"Tirdea, Irina" <irina.tirdea@...el.com>
To:	Bastien Nocera <hadess@...ess.net>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"Purdila, Octavian" <octavian.purdila@...el.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH v3 3/5] Input: goodix - add power management support

> -----Original Message-----
> From: linux-input-owner@...r.kernel.org [mailto:linux-input-owner@...r.kernel.org] On Behalf Of Bastien Nocera
> Sent: 30 June, 2015 18:56
> To: Tirdea, Irina; Dmitry Torokhov; Mark Rutland; linux-input@...r.kernel.org; devicetree@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org; Rob Herring; Pawel Moll; Ian Campbell; Kumar Gala; Purdila, Octavian
> Subject: Re: [PATCH v3 3/5] Input: goodix - add power management support
> 
> On Mon, 2015-06-29 at 19:28 +0300, Irina Tirdea wrote:
> > Implement suspend/resume for goodix driver.
> >
> > The suspend and resume process uses the gpio pins.
> > If the device ACPI/DT information does not declare gpio pins,
> > suspend/resume will not be available for these devices.
> >
> > This is based on Goodix datasheets for GT911 and GT9271
> > and on Goodix driver gt9xx.c for Android (publicly available
> > in Android kernel trees for various devices).
> 
> How can I functionally test this?

We are testing the power management feature by putting the system
in suspend and measuring the power consumed by the touchscreen
using HW measurement tools.

I can send a set of patches that export an interface to put
the touchscreen into suspend from sysfs (something similar to
what ads7846 has). In this way you can test what happens to
the touchscreen alone without putting the entire system into
suspend.

When suspending the device you will see that there are no events
received from the touchscreen (the interrupt is unregistered before
suspending the device). To actually check that the device
has been suspended and is not consuming power you need to measure
the power consumed by the touchscreen. To do that entirely from
software, you could compare the power consumed by the battery when the
touchscreen is powered on with the power consumed by the battery
when the touchscreen is powered off (batteries export interfaces in
sysfs that can be used for that). The difference should match the
device specifications. I am doing some tests to see how that works,
but I am not getting the expected results so far (seems there are other
components that affect the measurements). I will look more into this and
come back with details if you think this would work for you.

Thanks,
Irina

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