[PATCH 1/2] ARM: dts: sun4i: a10-lime: Override and remove 1008MHz OPP setting

[Chen-Yu Tsai]

On Thu, Mar 19, 2015 at 2:57 PM, Siarhei Siamashka
<siarhei.siamashka at gmail.com> wrote:
> On Thu, 19 Mar 2015 10:39:32 +0800
> Chen-Yu Tsai <wens at csie.org> wrote:
>
>> The Olimex A10-Lime is known to be unstable when running at 1008MHz.
>>
>> Signed-off-by: Chen-Yu Tsai <wens at csie.org>
>> ---
>>  arch/arm/boot/dts/sun4i-a10-olinuxino-lime.dts | 14 ++++++++++++++
>>  1 file changed, 14 insertions(+)
>>
>> diff --git a/arch/arm/boot/dts/sun4i-a10-olinuxino-lime.dts b/arch/arm/boot/dts/sun4i-a10-olinuxino-lime.dts
>> index 31dc2f1c3870..16ecb8938e19 100644
>> --- a/arch/arm/boot/dts/sun4i-a10-olinuxino-lime.dts
>> +++ b/arch/arm/boot/dts/sun4i-a10-olinuxino-lime.dts
>> @@ -74,6 +74,20 @@
>>       status = "okay";
>>  };
>>
>> +&cpu0 {
>> +     /* The A10-Lime is known to be unstable when running at 1008 MHz */
>> +     operating-points = <
>> +             /* kHz    uV */
>> +             960000  1400000
>> +             912000  1400000
>> +             864000  1300000
>> +             720000  1200000
>> +             528000  1100000
>> +             312000  1000000
>> +             144000  900000
>> +             >;
>> +};
>> +
>>  &ehci0 {
>>       status = "okay";
>>  };
>
> Thanks for the patch. At least it should make my A10-OLinuXino-LIME
> working without obvious failures out of the box (the U-Boot is still
> another story though and there is a gap during boot up when the board
> is running with unreliable settings, but the probability of a failure
> is rather low).
>
> 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@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.
>
> Anyway, this particular patch is
> Tested-by: Siarhei Siamashka <siarhei.siamashka at gmail.com>
> Acked-by: Siarhei Siamashka <siarhei.siamashka at gmail.com>

Good to hear it works. Did you test all the settings? I copied the
wrong settings, from sun5i-a13.dtsi instead of sun4i-a10.dtsi.

I'll send a fixed version later.


ChenYu