From: Guenter Roeck <linux@roeck-us.net>
To: Wolfram Sang <wsa@the-dreams.de>
Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] eeprom: at24: Add support for large EEPROMs connected to SMBus adapters
Date: Fri, 27 Mar 2015 08:42:02 -0700 [thread overview]
Message-ID: <55157A4A.1090305@roeck-us.net> (raw)
In-Reply-To: <20150327152727.GA27238@katana>
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
next prev parent reply other threads:[~2015-03-27 15:42 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-04 16:23 [PATCH] eeprom: at24: Add support for large EEPROMs connected to SMBus adapters Guenter Roeck
2015-02-04 17:47 ` Wolfram Sang
2015-02-04 19:08 ` Guenter Roeck
2015-02-04 23:35 ` Wolfram Sang
2015-02-05 0:26 ` Guenter Roeck
2015-02-05 14:40 ` Wolfram Sang
2015-02-05 17:53 ` Guenter Roeck
2015-02-12 4:01 ` Guenter Roeck
2015-02-16 12:09 ` Wolfram Sang
2015-02-16 15:37 ` Guenter Roeck
2015-03-17 4:20 ` Guenter Roeck
2015-03-18 13:27 ` Wolfram Sang
2015-03-19 3:24 ` Guenter Roeck
2015-03-19 8:16 ` Wolfram Sang
2015-03-19 13:30 ` Guenter Roeck
2015-03-19 17:43 ` Guenter Roeck
2015-03-19 21:39 ` Wolfram Sang
2015-03-25 14:11 ` Guenter Roeck
2015-03-25 16:15 ` Wolfram Sang
2015-03-25 16:37 ` Guenter Roeck
2015-03-27 8:09 ` Wolfram Sang
2015-03-27 12:51 ` Guenter Roeck
2015-03-27 13:01 ` Wolfram Sang
2015-03-27 13:14 ` Guenter Roeck
2015-03-27 15:27 ` Wolfram Sang
2015-03-27 15:42 ` Guenter Roeck [this message]
2015-02-04 20:33 ` Guenter Roeck
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