linux-kernel - Re: [PATCH 8/9] input: goodix: add support for ESD

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Date:	Fri, 5 Jun 2015 09:46:02 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	"Tirdea, Irina" <irina.tirdea@...el.com>
Cc:	Bastien Nocera <hadess@...ess.net>,
	Mark Rutland <mark.rutland@....com>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 8/9] input: goodix: add support for ESD

On Fri, Jun 05, 2015 at 04:37:49PM +0000, Tirdea, Irina wrote:
> 
> 
> > -----Original Message-----
> > From: Bastien Nocera [mailto:hadess@...ess.net]
> > Sent: 04 June, 2015 15:58
> > To: Tirdea, Irina
> > Cc: Mark Rutland; Dmitry Torokhov; linux-input@...r.kernel.org; devicetree@...r.kernel.org; linux-kernel@...r.kernel.org
> > Subject: Re: [PATCH 8/9] input: goodix: add support for ESD
> > 
> > On Thu, 2015-05-28 at 14:26 +0000, Tirdea, Irina wrote:
> > >
> > > > -----Original Message-----
> > > > From: linux-input-owner@...r.kernel.org [mailto:
> > > > linux-input-owner@...r.kernel.org] On Behalf Of Mark Rutland
> > > > Sent: 28 May, 2015 16:24
> > > > To: Tirdea, Irina
> > > > Cc: Dmitry Torokhov; Bastien Nocera; linux-input@...r.kernel.org;
> > > > devicetree@...r.kernel.org; linux-kernel@...r.kernel.org
> > > > Subject: Re: [PATCH 8/9] input: goodix: add support for ESD
> > > >
> > > > On Thu, May 28, 2015 at 01:47:44PM +0100, Irina Tirdea wrote:
> > > > > Add ESD (Electrostatic Discharge) protection mechanism.
> > > > >
> > > > > The driver enables ESD protection in HW and checks a register
> > > > > to determine if ESD occurred. If ESD is signalled by the HW,
> > > > > the driver will reset the device.
> > > > >
> > > > > The ESD poll time (in ms) can be set through
> > > > > esd-recovery-timeout-ms ACPI/DT property. If it is set to 0,
> > > > > ESD protection is disabled.
> > > > >
> > > > > Signed-off-by: Irina Tirdea <irina.tirdea@...el.com>
> > > > > ---
> > > > >  .../bindings/input/touchscreen/goodix.txt          |   4 +
> > > > >  drivers/input/touchscreen/goodix.c                 | 106
> > > > > ++++++++++++++++++++-
> > > > >  2 files changed, 106 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git
> > > > > a/Documentation/devicetree/bindings/input/touchscreen/goodix.txt
> > > > b/Documentation/devicetree/bindings/input/touchscreen/goodix.txt
> > > > > index 9e4ff69..9132ee0 100644
> > > > > ---
> > > > > a/Documentation/devicetree/bindings/input/touchscreen/goodix.txt
> > > > > +++
> > > > > b/Documentation/devicetree/bindings/input/touchscreen/goodix.txt
> > > > > @@ -19,6 +19,10 @@ Optional properties:
> > > > >
> > > > >   - device-config : device configuration information
> > > > > (specified as byte
> > > > >                     array). Maximum size is 240 bytes.
> > > > > + - esd-recovery-timeout-ms : ESD poll time (in milli seconds)
> > > > > for the driver to
> > > > > +                      check if ESD occurred and in that
> > > > > case reset the
> > > > > +                      device. ESD is disabled if this
> > > > > property is not set
> > > > > +                      or is set to 0.
> > > >
> > > > This sounds like software configuration rather than HW description.
> > > > Is
> > > > there any reason this needs to be a DT property?
> > > >
> > >
> > > Although this enables a software feature, it depends on the platform
> > > if electrostatic discharge
> > > protection should be enabled or not. Some platform designs handle ESD
> > > better and do not need
> > > the SW mechanism, so the property can be used to disable it.

Even though it depends on the platform it describes software function,
not hardware. Since it is not necessary for starting the device maybe we
should indeed export it through sysfs and userspace board code should
activate it as needed?

I'll leave the decision to DT folks here.

Thanks.

-- 
Dmitry
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