linux-kernel - Re: [PATCH 3/3] ARM: tegra: set SM2 voltage correct

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <ab16891b4a6bcfbb1854aa766e4926a7@agner.ch>
Date:	Sat, 30 Nov 2013 17:24:14 +0100
From:	Stefan Agner <stefan@...er.ch>
To:	Lucas Stach <l.stach@...gutronix.de>
Cc:	Stephen Warren <swarren@...dotorg.org>, thierry.reding@...il.com,
	sameo@...ux.intel.com, dev@...xeye.de, mark.rutland@....com,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/3] ARM: tegra: set SM2 voltage correct

Am 2013-11-28 10:49, schrieb Lucas Stach:
> Am Mittwoch, den 27.11.2013, 10:13 -0700 schrieb Stephen Warren:
>> On 11/26/2013 04:45 PM, Stefan Agner wrote:
>> > Set the requested SM2 voltage to the correct value of 1.8V. The value
>> > before used to work on TPS658623 since the driver applied a wrong
>> > voltage table too. However, the TPS658643 used on newer devices uses
>> > yet another voltage table and those broke that compatibility. The
>> > regulator driver now has the correct voltage table for both regulator
>> > versions and those the correct voltage can be used in this device
>> > tree.
>>
>> One thing you haven't called out explicitly here is that this series is
>> an incompatible change to the DT, since the old buggy driver used to
>> allow old buggy DT content to accidentally work.
>>
> The current (wrong and potentially dangerous) DT content only worked on
> the engineering sample models. So this change definitely does improve
> the situation, even with the risk of breaking a small fraction of
> working boards.
On the released modules, the current value ends in a freeze during
boot-up (since the wrong voltage table results in a too low voltage).

When I use 1.8V in the device tree, the old drivers refuses to set any
voltage. The regulators default/bootloader settings work then better
than the wrongfully applied values (tested on a new device). The probe
just fails:

[    0.243864] tps6586x-regulator tps6586x-regulator: failed to register
regulator REG-SM_2
[    0.244317] tps6586x-regulator: probe of tps6586x-regulator failed
with error -22

So, for newer modules, the incompatible 1.8V DT results in a successful
boot. Since we don't have a regulator driver at all, likely other things
are broken at that situation...

--
Stefan
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/