From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: [PATCH v4] i2c: davinci: Fix race when setting up for TX Date: Mon, 27 Sep 2010 07:16:41 -0700 Message-ID: <87sk0vuv92.fsf@deeprootsystems.com> References: <4C97CEC9.8060602@boundarydevices.com> <1285042408-13200-1-git-send-email-jon.povey@racelogic.co.uk> <87sk0zky28.fsf@deeprootsystems.com> <20100924163754.GH27885@trinity.fluff.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <20100924163754.GH27885-SMNkleLxa3Z6Wcw2j4pizdi2O/JbrIOy@public.gmane.org> (Ben Dooks's message of "Fri, 24 Sep 2010 17:37:54 +0100") Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ben Dooks Cc: Ben Dooks , 'Jon Povey' , davinci-linux-open-source-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Sudhakar Rajashekhara List-Id: linux-i2c@vger.kernel.org Ben Dooks writes: > On Fri, Sep 24, 2010 at 07:37:03AM -0700, Kevin Hilman wrote: >> "Sudhakar Rajashekhara" 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 >> >> CC: Sudhakar Rajashekhara >> >> CC: Troy Kisky >> >> --- >> > >> > Tested-by: Sudhakar Rajashekhara >> > >> > 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: > > If it is a worthwhile bugfix i'll send it for the next -rc. OK, yeah. It's probably better to queue for the next -rc. Thanks, Kevin