linux-kernel - Re: [PATCH 4/6] nvmem: sunxi_sid: Read out data in native format

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Date:   Mon, 18 Mar 2019 16:45:19 +0800
From:   Chen-Yu Tsai <wens@...nel.org>
To:     Maxime Ripard <maxime.ripard@...tlin.com>
Cc:     Chen-Yu Tsai <wens@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/6] nvmem: sunxi_sid: Read out data in native format

On Mon, Mar 18, 2019 at 4:42 PM Maxime Ripard <maxime.ripard@...tlin.com> wrote:
>
> Hi,
>
> On Mon, Mar 18, 2019 at 03:33:52PM +0800, Chen-Yu Tsai wrote:
> > From: Chen-Yu Tsai <wens@...e.org>
> >
> > Originally the SID e-fuses were thought to be in big-endian format.
> > Later sources show that they are in fact native or little-endian.
> > The most compelling evidence is the thermal sensor calibration data,
> > which is a set of one to three 16-bit values. In native-endian they
> > are in 16-bit cells with increasing offsets, whereas with big-endian
> > they are in the wrong order, and a gap with no data will show if there
> > are one or three cells.
> >
> > Switch to a native endian representation for the nvmem device. For the
> > H3, the register read-out method was already returning data in native
> > endian. This only affects the other SoCs.
> >
> > Signed-off-by: Chen-Yu Tsai <wens@...e.org>
>
> I thought only the newer SoCs were impacted by this issue?

It is noticable on the newer SoCs. The old ones only have the 128-bit SID,
which could be read either way, as AFAIK it's just a serial number.

If you think we should leave the old ones alone I can factor that in.

ChenYu