Ben Dooks <ben-i2c@xxxxxxxxx> writes: > 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? Please apply with: Acked-by: Troy Kisky <troy.kisky@xxxxxxxxxxxxxxxxxxx> Tested-by: Sudhakar Rajashekhara <sudhakar.raj@xxxxxx> Acked-by: Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx> -- 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
