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 -- 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
