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

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Date:	Thu, 04 Jun 2015 14:57:55 +0200
From:	Bastien Nocera <hadess@...ess.net>
To:	"Tirdea, Irina" <irina.tirdea@...el.com>
Cc:	Mark Rutland <mark.rutland@....com>,
	Dmitry Torokhov <dmitry.torokhov@...il.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 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.
> 
> I also saw an example in 
> Documentation/devicetree/bindings/input/touchscreen/tsc2005.txt
> and I though this is the standard way to use it.

As for the configuration data, is this useful/used on ACPI?

> > Can we not just choose a sensible default and allow this to be
> > overridden dynamically?
> 
> I could separate the enabling part from the actual poll timeout by 
> using a DT property to enable/disable
> ESD and a sysfs property to set the timeout. I can also move this 
> over to sysfs entirely if you prefer.

If this needs to be in the DT for some devices, and isn't available
from ACPI, maybe we should have a list of DMI matches for ACPI instead,
with a module option to override it?

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