[lm-sensors] [PATCH] Fix the AMD756 SMBus Controller hang

Rudolf Marek r.marek at sh.cvut.cz
Wed Jun 7 23:19:36 CEST 2006

Hello all,

> I don't like it. This is basically doubling the amount of sleep time
> for all simple transactions. For HZ=100, this means 10 ms of
> additional delay per transaction. For an EEPROM dump, this means 5
> seconds instead of 2.5 seconds, this makes a big difference. This is
> true also for I2C/SMBus hardware monitoring chips with a large number of
> registers.

Typical system has HZ 250 which is 4ms of wait. so like 1s all in all.
But more likely there is aneed to read 30 registers every 2 seconds
or so so it should be still enough.

> Given that the problem was only reported on one system by one user,
> it's quite a high price to pay, don't you think? I'd like this to be
> investigated further. Can we find other reports which could be related
> to the same problem? If not, why this one system has the problem when
> others don't? If we can understand that, maybe we can add the delay
> only when it is really needed, this would limit the impact of the
> change and make it more acceptable.

Well we cannot detect it, nor we know more. We know that this fixes the problem.
Given by cut & paste design of smbus controller it is likely to have this 
problem with others...

> Rudolf, I also see that you alreay applied this change to lm_sensors
> CVS, with the mention "backport of 2.6". That's not the right way to do
> it, sorry. For one thing you can't technically backport something
> before it was accepted and applied. For another, non-critical fixes
> should really get some broad testing in 2.6 before being actually
> backported.

Well I consider it critical because the bus will stop working at all. The delay
is anoying but "better safe than sorry"

Is anyone here with AMD southbridge for further testing?


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