linux-kernel - Re: [PATCH v2 1/3] input: sun4i-a10-lradc-keys: Add support for A83T

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Date:   Fri, 23 Jun 2017 16:46:22 +0200
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Ziping Chen <techping.chan@...il.com>
Cc:     Chen-Yu Tsai <wens@...e.org>, robh+dt@...nel.org,
        mark.rutland@....com, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH v2 1/3] input: sun4i-a10-lradc-keys: Add support for A83T

On Thu, Jun 22, 2017 at 12:50:47PM +0800, Ziping Chen wrote:
> 2017-06-22 4:35 GMT+08:00 Maxime Ripard <maxime.ripard@...e-electrons.com>:
> 
> > On Tue, Jun 20, 2017 at 09:44:43PM +0800, Ziping Chen wrote:
> > > From: Ziping Chen <techping.chan@...il.com>
> > >
> > > Allwinner A83T SoC has a low res adc like the one
> > > in Allwinner A10 SoC, however, the A10 SoC's vref
> > > of lradc internally is divided by 2/3 and the A83T
> > > SoC's isn't, thus add a hardware variant for it to
> > > be compatible with various devices.
> >
> > Where did you get that info from?
> >
> > Judging from the user manual, the threshold is actually set to 3/4,
> > and not 2/3, but there's still one.
> >
> 
> In the top of page 266 of the A10 User Manual V1.50, it said "2/3 ADC_REF
> (Level A)" which mean Level A is 2/3 of the vref.
> 
> In the bottom of page 230 of the A83T User Manual V1.5.1, it said "1.35V
> (Level A)" meaning that Level A is 1.35V. Oh, it's my fault... It's 3/4 of
> the vref (A83T's ADC_REF is fixed at 1.8V).
> 
> So... i will change r_lradc_variant_a83t.divisor_numerator to 3
> and r_lradc_variant_a83t.divisor_denominator to 4...
> 
> Is there any other problems?

I don't see any :)

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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