[Skiboot] [PATCH v2] hw/p8-i2c: Fix OCC locking

[ppaidipe]

On 2017-08-25 10:59, Stewart Smith wrote:
> Oliver O'Halloran <oohall at gmail.com> writes:
>> There's a few issues with the Host<->OCC I2C bus handshaking. First 
>> up,
>> skiboot is currently examining the wrong bit when checking if the OCC
>> is currently using the bus. Secondly, when we need to wait for the OCC
>> to release the bus we are scheduling a recovery timer to run zero
>> timebase ticks after the current moment so the recovery timeout 
>> handler
>> will run immediately after the bus was requested, which will in turn
>> re-schedule itself, etc, etc. There's also a race between the OCC
>> interrupt and the recovery handler which can result in an assertion
>> failure in the recovery thread. All of this is bad.
>> 
>> This patch addresses all these issues and sets the recovery timeout to
>> 10ms.
>> 
>> Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
>> ---
>>  hw/p8-i2c.c | 58 
>> +++++++++++++++++++++++++++++++++++++---------------------
>>  1 file changed, 37 insertions(+), 21 deletions(-)
>> ---
>> I've been using this script to test the changes. With this patch it's 
>> fairly
>> stable, but there's still intermittent data corruption issues when
>> when reading from the bus which I'm still investigating.
>> ---
>> #!/bin/bash -e
>> 
>> while true;
>> do
>> 	for f in $(find /sys/devices/platform/ -name '*-????'|grep a3000 )
>> 	do
>> 		bus="$(basename $f | awk -F - -- '{ print $1 }' )"
>> 		dev="$(basename $f | awk -F - -- '{ print $2 }' )"
>> 
>> 		i2cdump -y $bus 0x$dev i  > $bus-$dev
>> 		md5sum $bus-$dev
>> 		sleep 0.1
>> 	done
>> done
> 
> 
> Pridhiviraj, could you have a look at adding something to our EEPROM
> tests in op-test-framework to do something like the above? That is,
> md5sum the result of reading it and read the eeprom in a loop a few
> times.
> 
> (that is, if we don't already have that test there)

Stewart, added the above one here, Please take a look at it.

https://github.com/open-power/op-test-framework/pull/156/commits/c3a1ebd41cb02d5591e929c5a1b9e1c92b9a2ec1

Thanks
Pridhiviraj