Openblocks AX3-4 i2c bus lockup

[Gregory CLEMENT]

Hi Andrew,

On 22/12/2013 00:06, Gregory CLEMENT wrote:
> Hi Andrew,
> 
> I am away this weekend (Christmas with the first part of the family).
> 
> But I remember having few issue on i2c with the first AX3-4 I received. With the second one (using a B0 steping CPU), I didn't remember having any issues. As I thought the first AX3-4 I
> received was an early release I didn't paid more attention. The last i2c patches I sent were tested on the AX3-4 CPU rev B.
> 
> Could you tell me what kind of command did you do to get your issues ? Then I will try to reproduce it on Monday on both revision
> 
> Thanks,
> 
> Gregory


Sorry to not have answered earlier but when I investigated it I found
an unexpected issue.

First I wanted to be sure that there the issue was not introduce by a
commit so reverted one by one the commits on the file
drivers/i2c/busses/i2c-mv64xxx.c. I tested it on both version of the
OpenBlock AX-4 (with CPU A0 and B0). After each commit the kernel
continue to work on the B0 version as expected, but it was when I
reverted the commit "i2c: mv64xxx: Add I2C Transaction Generator
support" that it worked also on the A0 version.

Then I had a look on the errata datasheet and I found issues that I
missed when I worked on it. This issues were fixed in B0 version.

The fix should be pretty simple: disabling the offload_enabled flag when
an A0 version of the CPU is used. For this there are 2 solutions:
introducing a new compatible string or trying to detect the CPU
stepping at runtime. I would prefer the second solution and I am looking
for a way to get this information.

Thanks,

Gregory


> 
> Le 21 déc. 2013 17:43, "Andrew Lunn" <andrew at lunn.ch <mailto:andrew at lunn.ch>> a écrit :
> 
>     Hi Nobuhiro
> 
>     You added I2C into the Openblocks AX3-4 device tree and the subnode
>     for the RTC. Did you have any problems with I2C? I'm having lots of
>     problems with my AX3-4 and i2c. I get i2c errors and the bus being
>     locked and then the whole machine locks solid.
> 
>     Gregory, did you test your I2C patches for 370/XP on an Openblocks
>     AX3-4?
> 
>     Thanks
>             Andrew
> 
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-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com