[linux-sunxi] Re: [PATCH 1/2] ARM: dts: sun4i: a10-lime: Override and remove 1008MHz OPP setting - Chen-Yu Tsai

From: wens@csie.org (Chen-Yu Tsai)
To: linux-arm-kernel@lists.infradead.org
Subject: [linux-sunxi] Re: [PATCH 1/2] ARM: dts: sun4i: a10-lime: Override and remove 1008MHz OPP setting
Date: Thu, 26 Mar 2015 10:56:00 -0700	[thread overview]
Message-ID: <CAGb2v67+sxLXs3ukJ3LRBn5Q=DCk0RNCu6TPiicOzPDssKaq1g@mail.gmail.com> (raw)
In-Reply-To: <55143ACF.9070800@gmail.com>

Hi,

On Thu, Mar 26, 2015 at 9:58 AM, Iain Paton <ipaton0@gmail.com> wrote:
> On 19/03/15 06:57, Siarhei Siamashka wrote:
>
>> I should also mention that using 960MHz @1.4V does not fail, but it does
>> not have any safety headroom either (the cyan 'sun4i_poorlime' line
>> on the plot):
>>
>>     http://people.freedesktop.org/~siamashka/files/20140512/sunxi-cpufreq-plot.png
>>
>> On the other hand, my board is on the worst part of the spectrum (many
>> other a10-lime boards do not fail even at 1008MHz), so maybe having
>> extra safety headroom is less necessary.
>>
>> An interesting question is whether the same problem may be reproducible
>> on the Allwinner A10 devices other than A10-OLinuXino-LIME. My original
>> problem report
>>
>>     https://www.mail-archive.com/linux-sunxi at googlegroups.com/msg04343.html
>>
>> mentioned the A10-OLinuXino-LIME rev.A and introduced some sort of
>> a bias by itself. At least I have seen people saying something like
>> "my a10-lime revision is not rev.A, so it's none of my concern and
>> I'm not going to bother running any tests". So far we have accumulated
>> reports from 4 or 5 people having this reliability problem on their
>> A10-OLinuXino-LIME (various revisions, not just rev.A), but not
>> much from the other boards owners.
>
> I'm somewhat sad to see 1008MHz go. I have 2x revA A10-Lime boards that
> are stable at 1008MHz with Maximes sunxi/for-next, a full regulator
> description in the dts and a very recent u-boot. They are not stable at
> 1056 or above however.
>
>
> Can I ask what the basis is for the 960MHz setting?  I don't see any
> instances of it in any of the a10 fex files, meaning it's likely not
> very well tested.

It was copied from the wrong file. Please see v2 of the series.

> If there's interest, I'll send the patch adding regulators to the dts for
> the a10-lime.

Please do.

ChenYu