Messages in this thread | | | Date | Fri, 27 Mar 2015 08:42:02 -0700 | From | Guenter Roeck <> | Subject | Re: [PATCH] eeprom: at24: Add support for large EEPROMs connected to SMBus adapters |
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On 03/27/2015 08:27 AM, Wolfram Sang wrote: > 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. > I pushed it into my linux repository at github (https://github.com/groeck/linux, branch at24).
>> 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? > yes.
>> >> 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? > In this case, I just used i2cdump from one session while accessing the chip from another session using the driver.
Guenter
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