On Tue, Sep 21, 2010 at 12:17:58PM -0700, Troy Kisky wrote: > 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. > > Thanks as well > Troy Ok, any objections to this being applied, or should I wait? -- Ben Q: What's a light-year? A: One-third less calories than a regular year. -- 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
