[Voyage-linux] RE: [lm-sensors] scx200_acb: unexpected ACBCTL2 readback

BGardner at Wabtec.com BGardner at Wabtec.com
Tue Jan 3 23:49:52 HKT 2006


Hi Mike, Joe -

It looks like the scx200_acb driver scans two IO addresses by default
(0x820, 0x840).
One of them doesn't exist. That explains the ACBCTL2 readback problem.
=)
You should be able to get rid of that message by using the 'base' module
parameter.
Here's a guess at the format.
$ modprobe scx200_acb base=0x820,0


In [1], Joe mentioned a 15 second delay.

The scx200_acb driver has a flaw where it misses the NACK indication
when it tries to write to an address that doesn't exist. This causes it
to timeout instead of immediately returning a failure.  Likely, your
hardware is 'scanning' for around 15 devices that don't exist. 

Refer to this patch for a possible fix: 
http://lists.lm-sensors.org/pipermail/lm-sensors/2005-December/014716.ht
ml

Another thing to do is to add 'ignore' parameters to modprobe so that
the chip drivers don't scan for devices that don't exist.

For example, I use this for my lm83:
$ modprobe lm83 force=0,0x4c
ignore=0,0x18,0,0x19,0,0x1a,0,0x29,0,0x2a,0,0x2b,0,0x4d,0,0x4e

Ben

> -----Original Message-----
> From: lm-sensors-bounces at lm-sensors.org 
> [mailto:lm-sensors-bounces at lm-sensors.org] On Behalf Of 
> Michael Renzmann
> Sent: Tuesday, January 03, 2006 1:53 AM
> To: lm-sensors
> Subject: [lm-sensors] scx200_acb: unexpected ACBCTL2 readback
> 
> Hi.
> 
> On the voyage-linux mailing list there recently has been a 
> report about
> a problem related to scx200_acb in 2.6.x kernels. The 
> original report is
> at [1], a short but more detailed analysis of the problem is at [2]. 
> 
> The problem seems to be that loading scx200_acb fails during 
> the probing
> phase, but loading and using LM77 after that still works fine. Quoting
> [2]:
> 
> === cut ===
> Same here with a non-voyage 2.6.11 kernel. I enabled 
> debugging and added
> a bit more info into the relevant message and I get:
> 
> i2c /dev entries driver
> scx200_acb: ACBCTL2 readback failed, got 0xff
>   : probe failed
> 
> The driver write 0x70 to ACBCTL2 and expects to read 0x70 back, but it
> gets 0xff instead. Looked into the manual briefly, but seems too
> complicated to figure out quickly. As you mention, lm77 works fine
> thereafter. Weird...
> === cut ===
> 
> Comments?
> 
> Bye, Mike
> 
> [1]
> http://list.voyage.hk/pipermail/voyage-linux/2005-December/000548.html
> [2]
> http://list.voyage.hk/pipermail/voyage-linux/2006-January/000565.html
> 
> 
> _______________________________________________
> lm-sensors mailing list
> lm-sensors at lm-sensors.org
> http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
> 
> 




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