On 9/23/2010 7:27 AM, Kevin Hilman wrote: > Troy Kisky <troy.kisky@xxxxxxxxxxxxxxxxxxx> writes: > >> On 9/21/2010 4:24 AM, Sudhakar Rajashekhara wrote: >>> Hi, >>> >>> 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@xxxxxxxxxxxxxxx> >>>> CC: Sudhakar Rajashekhara <sudhakar.raj@xxxxxx> >>>> CC: Troy Kisky <troy.kisky@xxxxxxxxxxxxxxxxxxx> >>>> --- >>>> Reworked after comments by Troy and Sudhakar. >>>> >>>> Looking at the datasheet it seemed like setting STP without STT early >>>> might cause a stray STOP to be generated, so I moved it into the second >>>> MDR load. >>>> >>>> This passes a quick smoke test but I can't do much more testing right at >>>> the moment. Sudhakar, your comments would be welcomed. >>>> >>> >>> Looks good to me. I can test on couple of platforms I have and update the result >>> by tomorrow. >>> >>> Thanks, >>> Sudhakar >>> >>> >>> >> I like it too. I hope it works for omap. > > Troy, can I take this as an Acked-by from you? or a Tested-by? > > Thanks, > > Kevin > Acked-by is fine, but I didn't test it. Troy -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
