[U-Boot] [linux-sunxi] [PATCH 5/7] sun4i: Add support for a number of new sun4i boards

[Arnd Gronenberg <arnd@gronenberg.com>]

On 09/28/2014 05:58 PM, Hans de Goede wrote:
> [...]
>
> On 09/18/2014 06:07 PM, Siarhei Siamashka wrote:
>> Which revision of A10-OLinuXino-LIME do you have? Revision A is known
>> to have troubles running stable at 1008MHz CPU clock speed, as confirmed
>> on a sample set of two boards (mine and Oliver Schinagl's):
>>      https://www.mail-archive.com/linux-sunxi at googlegroups.com/msg04343.html
> I have a revision A board.
My Olimex A10 OLinuXino Lime is also labelled "Rev. A"... It is running 
stable at 1008MHz and I just tried Olivers djpeg test without any problems.

I'm running Hans' u-boot-sunxi 2014.10-rc1-g7190869 and Linux mainline 
3.17.0-rc1-00158-g451fd72.
>> A bunch of revision C boards were all fine in Oliver's tests. And
>> nobody has ever tested revision B so far, so we have no idea whether
>> it is stable or not. A mysterious thing is that the Olimex
>> representatives on IRC were not aware of any fixes of this kind
>> applied to the PCB.
>>
>> My understanding is that the revision A was just a small pre-production
>> batch, donated by OLIMEX to a number of open source developers. Some of
>> these boards were distributed at FOSDEM. I'm not sure if we should
>> really worry about the reliability of the revision A, because none of
>> the 'normal' customers probably have such boards. We only need to
>> clarify the status of revision B.
>>
>> But if we want to support the revision A too, then it probably needs
>> its own config, which would somehow restrict the CPU clock speed.
>> I also ha
> My revision A was actually ordered normally, a couple of days before
> the first batch sold-out. So it is likely that the entire first batch
> was revision A.
>
> Do you have any easy step-by-step document (or ready to use sdcard
> image to download) to do some stress tests on my revision A ?
>
> Maybe the first couple handed out to developers where hand soldered
> or some such ? Either way it would be good to either confirm that
> my revision A has the same issues, or not :)
I bought my revision A from a German distributor (exp-tech.de) and it 
doesn't look hand soldered (except for the through hole parts :-) ).

If I correctly compared the schematics for revision A,B and C, there is 
only one change in regard to the DRAM: R8 (connected to ZQ) has a 
different value:
- Revision A: 237 Ohm / 1%
- Revision B: 430 Ohm / 1%
- Revision C: 330 Ohm / 1%

I checked R8 on my revision A's PCB: It is a 330 Ohm / 1%, therefore the 
value specified in the revision C schematic. So it may make sense to 
check R8 on the problematic revision A boards and replace it by a 330 
Ohm resistor. The DRAM data sheet specifies this resistor with 240 Ohm / 
1%...
>> [...]
>>
>> Either way, these settings are outside of the valid range when running
>> at 480MHz (which would be something like DDR3-960 in our case).
>>
>> [...]
The current (probably incorrect) values work fine with my board (even 
though they may be out of spec), but the value of R8 may have some 
impact here.

Best regards, Arnd

-- 

Arnd Gronenberg, arnd at gronenberg.com, DJ9PZ / AB2QP


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