On Fri, Mar 27, 2015 at 06:14:28AM -0700, Guenter Roeck wrote: > On 03/27/2015 06:01 AM, Wolfram Sang wrote: > >On Fri, Mar 27, 2015 at 05:51:11AM -0700, Guenter Roeck wrote: > >>On 03/27/2015 01:09 AM, Wolfram Sang wrote: > >>> > >>>>just to give you an update: I do have some code, but it is a bit messy, > >>>>and it doesn't work well for ds2482 (the chip behind it still hangs up > >>>>if I access it in parallel through i2c-dev). On top of that, it causes > >>>>pretty significant slow-downs when accessing other devices on the same > >>>>bus at the same time. Not surprising, I guess, since it expands the scope > >>>>of the bus lock significantly. > >>> > >>>Just to get a better idea: Did you try taking the adapter_lock before > >>>the two SMBus command which needed to be concatenated (and use > >>>smbus_xfer directly)? > >>> > >>I did. I didn't use smbus_xfer directly, though, but introduced lockless > >>versions of the various smbus commands, and kept using those. > > > >And then the chip still hangs? Or was that the performance penalty here? > > > Parallel access to a second eeprom chip on the same bus was much slower > than before. Interesting. I wonder what is the reason, I would have expected just a small delay. Would you mind sending the patches for the non-locked smbus routines? Would be nice to have that around in case I or someone else find some time to try as well. > Also, the new code did not solve the problem for ds2482 (completely unrelated > to the at24 driver of course). Even with proper locking, the chip ended up > hanging after some parallel accesses through i2c-dev. Granted, ds2482 is > a difficult beast, but it is still annoying how access through i2c-dev > can mess it up. I assume you basically replaced the access_lock with the adapter_lock with this one? > > The latter is what bothered me more: What is the point of all this if we > still can not ensure correct operation ? Yeah, this is not good at all. How do you use i2c-dev BTW? i2c_rdwr_msgs? What about iterating over all msgs in that and check for busy addresses?
Attachment:
signature.asc
Description: Digital signature
