linux-kernel - Re: [PATCH v2] ARM: dts: sunxi: Add sid for a83t

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Message-ID: <CAGb2v64mf-ihyOs-WJZuVa4Yib3Szp90RZu_a1EeQ1LJXnoXEQ@mail.gmail.com>
Date:   Fri, 22 Dec 2017 18:11:52 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Emmanuel Vadot <manu@...ouilliste.com>
Cc:     Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Russell King <linux@...linux.org.uk>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        Rob Herring <robh+dt@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Kyle Evans <kevans91@....edu>, Chen-Yu Tsai <wens@...e.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] ARM: dts: sunxi: Add sid for a83t

On Fri, Dec 22, 2017 at 6:07 PM, Emmanuel Vadot <manu@...ouilliste.com> wrote:
> On Fri, 22 Dec 2017 09:35:08 +0100
> Maxime Ripard <maxime.ripard@...e-electrons.com> wrote:
>
>> On Thu, Dec 21, 2017 at 07:09:03PM +0100, Emmanuel Vadot wrote:
>> >
>> >  Hi Maxime,
>> >
>> > On Thu, 21 Dec 2017 16:26:30 +0100
>> > Maxime Ripard <maxime.ripard@...e-electrons.com> wrote:
>> >
>> > > Hi,
>> > >
>> > > On Thu, Dec 21, 2017 at 09:19:24AM -0600, Kyle Evans wrote:
>> > > > On Thu, Dec 21, 2017 at 8:55 AM, Maxime Ripard
>> > > > <maxime.ripard@...e-electrons.com> wrote:
>> > > > > Hi Kyle,
>> > > > >
>> > > > > On Tue, Dec 19, 2017 at 03:05:23PM -0600, kevans91@....edu wrote:
>> > > > >> Allwinner a83t has a 1 KB sid block with efuse for security rootkey and
>> > > > >> thermal calibration data, add node to describe it.
>> > > > >>
>> > > > >> a83t-sid is not currently supported by nvmem/sunxi-sid, but it is
>> > > > >> supported in an external driver for FreeBSD.
>> > > > >>
>> > > > >> Signed-off-by: Kyle Evans <kevans91@....edu>
>> > > > >
>> > > > > The patch looks fine in itself, but we've had a number of issues with
>> > > > > the register layout (and access patterns) in the past, so I'd rather
>> > > > > have something that works in Linux too if possible.
>> > > >
>> > > > I have a patch that I think should make it work fine on Linux [1], but
>> > > > I'm afraid I have little to no capability to test it myself and so I
>> > > > did not add it as well.
>> > > >
>> > > > I do know that the rootkey is offset 0x200 into the given space [2],
>> > > > as is the case with the H3, and that the readout quirk is not needed.
>> > > > I wasn't 100% sure that the a83t has 2Kbit worth of efuse space as the
>> > > > H3, but I do know that thermal data can be found at 0x34 and 0x38 in
>> > > > this space.
>> > >
>> > > Then maybe we should leave it aside until someone takes some time on
>> > > the A83t.
>> >
>> >  Take some time on the Linux driver and do not apply this patch for
>> > now you mean ?
>>
>> Yep.
>>
>> Maxime
>
>  Since linux doesn't have the compatible in it's driver what would
> be the harm to add the node in the DTS ? If a quirks is needed because
> some region is weird this would go in the driver right ? I don't see a
> technical problem for adding this node right now.
>  If Kyle confirm the lenght of the region and that no quirk is needed
> will it be enough ?

I guess I wasn't very clear. I'm OK with the patch going in. The device
node currently says nothing about how much efuse space there is. The
memory region covers that and the control section, and the size matches
what the memory map says.

The size and offset of the efuse space would be dealt with in the driver.


ChenYu