linux-kernel - Re: I2C filtering (was Re: [PATCH v2 6/9] dt-bindings: i2c: at91: add binding for enable-ana-filt)

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Message-ID: <20190627132200.GK3692@piout.net>
Date:   Thu, 27 Jun 2019 15:22:00 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Wolfram Sang <wsa@...-dreams.de>
Cc:     Eugen.Hristev@...rochip.com, peda@...ntia.se, robh+dt@...nel.org,
        mark.rutland@....com, Nicolas.Ferre@...rochip.com,
        Ludovic.Desroches@...rochip.com, linux-i2c@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        Pierre-Yves MORDRET <pierre-yves.mordret@...com>
Subject: Re: I2C filtering (was Re: [PATCH v2 6/9] dt-bindings: i2c: at91:
 add binding for enable-ana-filt)

On 25/06/2019 11:55:33+0200, Wolfram Sang wrote:
> On Tue, Jun 25, 2019 at 11:31:56AM +0200, Alexandre Belloni wrote:
> > On 25/06/2019 09:14:13+0000, Eugen.Hristev@...rochip.com wrote:
> > > > Perhaps
> > > > 
> > > > 	microchip,digital-filter;
> > > > 	microchip,analog-filter;
> > > > 
> > > > ?
> > > 
> > > Hi Peter,
> > > 
> > > Thanks for reviewing. The name of the property does not matter much to 
> > > me, and we have properties prefixed with vendor, and some are not.
> > > 
> > > @Alexandre Belloni: which name you think it's best ?
> > > 
> > 
> > I'm not sure, it depends on whether Wolfram thinks it is generic enough
> > to be used without a vendor prefix.
> 
> I could imagine that we design a generic property for filters. The ones
> above make me wonder, though, because they are bool. I'd think you can
> configure the filters in some way, too?
> 

Apart from enabling the filter there is indeed one configuration
setting, the maximum pulse width of spikes to be suppressed by the input
filter.

> I never used such filtering, so I am unaware of the parameters needed /
> suitable. Quick grepping through I2C master drivers reveals that
> i2c-stm32f7.c also handles filters, but only with default values. Maybe
> DT configuration would be benefitial to that driver, too?
> 
> Adding some people to CC.
> 



-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com