linux-kernel - Re: AXP803 I2C support / AXP devicetree-bindings

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAFBinCDVh2DpuQBx-x2OC_n9GJyYF8E84V1muYYvMJp2FYxjTQ@mail.gmail.com>
Date:   Tue, 7 Nov 2017 23:32:23 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Icenowy Zheng <icenowy@...c.io>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Quentin Schulz <quentin.schulz@...e-electrons.com>
Subject: Re: AXP803 I2C support / AXP devicetree-bindings

Hi ChenYu,

On Tue, Nov 7, 2017 at 4:13 AM, Chen-Yu Tsai <wens@...e.org> wrote:
> On Tue, Nov 7, 2017 at 6:39 AM, Martin Blumenstingl
> <martin.blumenstingl@...glemail.com> wrote:
>> Hello,
>>
>> recently I discovered that there are some X-Powers AXP chips that
>> support both, Allwinner's own "RSB" as well as the I2C ("TWSI" in the
>> datasheet) busses.
>>
>> one chip that supports both interfaces is the AXP803
>> the datasheet is linked in the public PINE64 wiki: [1] (direct link: [0])
>
> All the RSB based PMICs support both modes. They start in I2C mode
> when cold booted.
I did not know that - thank you for that info!

>>
>> currently the "x-powers,axp803" binding is "RSB" bus specific as it's
>> currently only listed in drivers/mfd/axp20x-rsb.c
>>
>> was there a discussion about supporting both, the "RSB" and I2C bus
>> for one chip (for example the AXP803) in the past (I couldn't find
>> anything online)?
>
> No. None of the boards actually use I2C instead of RSB. RSB mode is
> initialized by the boot loader. There is no easy way for the kernel to
> switch it back.
I'm not trying to change this on an existing board

>> what about the device-tree bindings in this case?
>
> We can deal with it if someone actually comes up with a practical
> case needing it. Otherwise things go untested, which is not what
> we want.
OK, thank you for this information

if there is a valid use-case for this: would you like to see a RfC
patch-series (along with a description why it's needed) or discuss
this further before sending any patches?


Regards
Martin