linux-kernel - Re: Allwinner SID THS calibration data cell representation?

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Message-ID: <20190220145531.xu2t5gklnien7a3i@flea>
Date:   Wed, 20 Feb 2019 15:55:31 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Philipp Rossak <embed3d@...il.com>,
        Emmanuel Vadot <manu@...ouilliste.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Cameron <jic23@...nel.org>,
        Quentin Schulz <quentin.schulz@...tlin.com>,
        Icenowy Zheng <icenowy@...c.io>, linux-iio@...r.kernel.org,
        devicetree <devicetree@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Allwinner SID THS calibration data cell representation?

On Tue, Feb 19, 2019 at 03:54:00PM +0800, Chen-Yu Tsai wrote:
> Sorry for resurrecting an old discussion, but since someone posted patches
> for H5 and H6, I thought we should resolve this. I'm working on patches to
> fix / replace the big-endian issue.
> 
> On Thu, Sep 6, 2018 at 7:51 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
> >
> > On Thu, Sep 06, 2018 at 01:47:47PM +0200, Philipp Rossak wrote:
> > > On 04.09.2018 18:46, Emmanuel Vadot wrote:
> > > > > +                 /* Data cells */
> > > > > +                 thermal_calibration: calib@234 {
> > > > > +                         reg = <0x234 0x8>;
> > > > > +                 };
> > > >   You are declaring 8 bytes of calibration data but to my knowledge it's
> > > > only 2 bytes per sensor, so 2 bytes for H3.
> > > >   Am I missing something ?
> > > >
> > > >   Thanks,
> > >
> > > Emmanuel you are right, it is 2 bytes per Sensor and should be 2 bytes for
> > > H3, but the thermal calibration data field is on all chips 64 bit wide - so
> > > 8 bytes. So I'm reading here the complete calibration data field.
> >
> > Having one cell per channel would make more sense I guess.
> 
> Would it? The 2 32-bit words directly map onto the registers 0x74 / 0x78 in
> the THS. As far as the SID is concerned, their is just one consumer for this
> data, the thermal sensor. How the thermal sensor uses that data is really not
> its concern. And the thermal sensor is really just copying the data from the
> e-fuses into its registers. Nothing more.
> 
> Furthermore, with the register access interface, the e-fuses are read/write
> 32 bits at a time. Seems to me it would make more sense to enforce a 32-bit
> word size, so cells should be multiples of 32 bits.

I guess you convinced me :)

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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