From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kevin Hilman <khilman-1D3HCaltpLuhEniVeURVKkEOCMrvLtNR@public.gmane.org>
Subject: Re: [PATCH v4] i2c: davinci: Fix race when setting up for TX
Date: Fri, 24 Sep 2010 07:37:03 -0700
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	<1285042408-13200-1-git-send-email-jon.povey@racelogic.co.uk>
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	Rajashekhara's message of "Fri, 24 Sep 2010 10:12:07 +0530")
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To: Ben Dooks <ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org>
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"Sudhakar Rajashekhara" <sudhakar.raj-l0cyMroinI0@public.gmane.org> writes:

> On Tue, Sep 21, 2010 at 09:43:28, Jon Povey wrote:
>> When setting up to transmit, a race exists between the ISR and
>> i2c_davinci_xfer_msg() trying to load the first byte and adjust counters.
>> This is mostly visible for transmits > 1 byte long.
>> 
>> The hardware starts sending immediately that MDR.STT is set. IMR trickery
>> doesn't work because if we start sending, finish the first byte and an
>> XRDY event occurs before we load IMR to unmask it, we never get an
>> interrupt, and we timeout.
>> 
>> Sudhakar Rajashekhara explains that at least OMAP-L138 requires MDR mode
>> settings before DXR for correct behaviour, so load MDR first with
>> STT cleared and later load again with STT set.
>> 
>> Tested on DM355 connected to Techwell TW2836 and Wolfson WM8985
>> 
>> Signed-off-by: Jon Povey <jon.povey-Ean/AyPsLtfkYMGBc/C6ZA@public.gmane.org>
>> CC: Sudhakar Rajashekhara <sudhakar.raj-l0cyMroinI0@public.gmane.org>
>> CC: Troy Kisky <troy.kisky-Q5RJGjKts06CY9SHAMCTRUEOCMrvLtNR@public.gmane.org>
>> ---
>
> Tested-by: Sudhakar Rajashekhara <sudhakar.raj-l0cyMroinI0@public.gmane.org>
>
> Tested with audio loopback on OMAP-L138, OMAP-L137 and DM365. Also tested with
> i2cdetect function which probes all the devices on the i2c bus.


Ben, can you queue this one for 2.6.37 with the addition of:

Acked-by: Troy Kisky <troy.kisky-Q5RJGjKts06CY9SHAMCTRUEOCMrvLtNR@public.gmane.org>
Tested-by: Sudhakar Rajashekhara <sudhakar.raj-l0cyMroinI0@public.gmane.org>
Acked-by: Kevin Hilman <khilman-1D3HCaltpLuhEniVeURVKkEOCMrvLtNR@public.gmane.org>

Thanks,

Kevin