Dear Lucas Stach, > Am Montag, den 01.07.2013, 18:14 -0300 schrieb Fabio Estevam: > > From: Fabio Estevam <fabio.estevam@xxxxxxxxxxxxx> > > > > Recently we have been seing some reports about PIO mode not working > > properly. > > > > - http://www.spinics.net/lists/linux-i2c/msg11985.html > > - http://marc.info/?l=linux-i2c&m=137235593101385&w=2 > > - https://lkml.org/lkml/2013/6/24/430 > > > > Let's use DMA mode even for small transfers. > > > > Without this patch, i2c reads the incorrect sgtl5000 version on a mx28evk > > when touchscreen is enabled: > > > > [ 5.856270] sgtl5000 0-000a: Device with ID register 0 is not a > > sgtl5000 [ 9.877307] sgtl5000 0-000a: ASoC: failed to probe CODEC -19 > > [ 9.883528] mxs-sgtl5000 sound.12: ASoC: failed to instantiate card > > -19 [ 9.892955] mxs-sgtl5000 sound.12: snd_soc_register_card failed > > (-19) > > > > Cc: <stable@xxxxxxxxxxxxxxx> > > Signed-off-by: Fabio Estevam <fabio.estevam@xxxxxxxxxxxxx> > > --- > > Applies against 3.10 > > > > Changes since v1: > > - Keep the PIO code > > > > drivers/i2c/busses/i2c-mxs.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c > > index 2039f23..6d8094d 100644 > > --- a/drivers/i2c/busses/i2c-mxs.c > > +++ b/drivers/i2c/busses/i2c-mxs.c > > @@ -494,7 +494,7 @@ static int mxs_i2c_xfer_msg(struct i2c_adapter *adap, > > struct i2c_msg *msg, > > > > * based on this empirical measurement and a lot of previous frobbing. > > */ > > > > i2c->cmd_err = 0; > > > > - if (msg->len < 8) { > > + if (0) { /* disable PIO mode until a proper fix is made */ > > > > ret = mxs_i2c_pio_setup_xfer(adap, msg, flags); > > if (ret) > > > > mxs_i2c_reset(i2c); > > I still plan to take another look at the PIO mode, but higher priority > things keep popping up in front of me. So this patch is: > Acked-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx> Ok, update. So far I arrived at a point where I can avoid the PIO trouble. If I only do transfers shorter or equal in length to 3 bytes via PIO, it works as expected. If the transfer is longer, the LA shows very long transfer happening actually. Therefore, the pumping of data in loop to/from PIO via the DATA register doesn't work. I will update you more later, once I figure out something else. Now I need some sleep. Best regards, Marek Vasut -- 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
