[i2c] [PATCH] Bugfixes for i2c-cpm.c

[Laurent Pinchart]

On Tuesday 01 July 2008, Laurent Pinchart wrote:
> On Friday 27 June 2008, Jochen Friedrich wrote:
> > Hi Laurent,
> > 
> > >> Bugfixes to the i2c-cpm driver
> > >>
> > >> - enable correct interrupts (I2CER_TXE instead of I2CER_BUSY)
> > >> - replace forgotten iic with i2c
> > >> - fix typo (devided)
> > >> - prefix debug-output on init with 0x and add frequency
> > >>
> > >> Signed-off-by: Wolfram Sang <w.sang at pengutronix.de>
> > > 
> > > Tested on a MPC8247 board. I have experienced I2C issues since migration
> > > from ppc to powerpc. This patch seems to solve the problem.
> > 
> > What kind of problems have this been? In normal operation there shouldn't
> > be any I2CER_TXE interrupts being generated.
> 
> I2C devices would frequently (about once every 10 cold boots) be undetected
> by the kernel. I tried to investigate the issue by hooking up a scope to the
> I2C signals, but haven't been able to reproduce the problem once the probes
> were connected.   
> 
> This might of course be a case of Murphy's law in action, but the problem
> disappeared after applying the patch. 

Seems Murphy's law was involved :-( I've run into the same issue just now.

[    0.555664] i2c /dev entries driver
[    0.564539] rtc-pcf8563 0-0051: chip found, driver version 0.4.3
[    0.570038] rtc-pcf8563 0-0051: rtc core: registered rtc-pcf8563 as rtc0
[    1.576209] i2c-adapter i2c-0: I2C transfer: timeout
[    1.579642] lm75: probe of 0-0048 failed with error -1
[snip]
[    2.766230] i2c-adapter i2c-0: I2C transfer: timeout
[    2.769602] rtc-pcf8563 0-0051: pcf8563_get_datetime: read error
[    2.775345] rtc-pcf8563 0-0051: hctosys: unable to read the hardware clock                                                               

The lm75 is there and works after a reboot. In this particular run the pcf8563 was detected, but it would sometimes time out during probe as well.

-- 
Laurent Pinchart
CSE Semaphore Belgium

Chaussee de Bruxelles, 732A
B-1410 Waterloo
Belgium

T +32 (2) 387 42 59
F +32 (2) 387 42 75
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