Hello, On Thu, Nov 20, 2014 at 12:03:05PM +0200, Grygorii Strashko wrote: > According to I2C specification the NACK should be handled as folowing: s/folowing/follows/ > "When SDA remains HIGH during this ninth clock pulse, this is defined as the Not > Acknowledge signal. The master can then gene rate either a STOP condition to s/gene rate/generate/ > abort the transfer, or a repeated START condition to start a new transfer." > [http://www.nxp.com/documents/user_manual/UM10204.pdf] The link is nice, but pointing out that this is the i2c spec would be nice. > The same is recomened by TI I2C wiki: s/recomened/recommended/ > http://processors.wiki.ti.com/index.php/I2C_Tips If the specification tells what to do, there is no need to further support your claim. > Currently, the Davinci I2C driver interrupts I2C trunsfer in case of NACK, but s/trunsfer/transfer/ > It queries Stop condition DAVINCI_I2C_MDR_REG.STP=1 only if NACK has been received s/It/it/ > during the last message transmitting/recieving. s/transmitting/transmitted/; s/recieving/received/ I think I don't understand this sentence even with the typos corrected. Do you want to say: Currently the Davinci i2c driver interrupts the transfer on receipt of a NACK but fails to send a STOP in some situations and so makes the bus stuck. > This may lead to Bus stuck in "Bus Busy" until I2C IP reset (idle/enable) if > during SMBus reading transaction the first I2C message is NACKed. Did you hit this problem, or is this a theoretical issue? Assuming this is a candidate for stable, adding a Fixes:-footer would be nice. > Hence, fix it by querying Stop condition (STP) always when NACK is received. > > This patch fixes Davinci I2C in the same way it was done for OMAP I2C > commit cda2109a26eb ("i2c: omap: query STP always when NACK is received"). > > More info can be found at: > https://lkml.org/lkml/2013/7/16/159 > http://patchwork.ozlabs.org/patch/249790/ I'd drop this "more info" paragraph. > CC: Sekhar Nori <nsekhar@xxxxxx> > CC: Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx> > CC: Santosh Shilimkar <ssantosh@xxxxxxxxxx> > CC: Murali Karicheri <m-karicheri2@xxxxxx> > Reported-by: Hein Tibosch <hein_tibosch@xxxxxxxx> Is this Reported-by tag reused from the omap issue? > Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx> > --- > drivers/i2c/busses/i2c-davinci.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c > index 9bbfb8f..2cef115 100644 > --- a/drivers/i2c/busses/i2c-davinci.c > +++ b/drivers/i2c/busses/i2c-davinci.c > @@ -411,11 +411,9 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop) > if (dev->cmd_err & DAVINCI_I2C_STR_NACK) { > if (msg->flags & I2C_M_IGNORE_NAK) > return msg->len; > - if (stop) { > - w = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG); > - w |= DAVINCI_I2C_MDR_STP; > - davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, w); > - } > + w = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG); > + w |= DAVINCI_I2C_MDR_STP; > + davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, w); I think this is a good change, but I wonder if the handling of I2C_M_IGNORE_NAK is correct here. If the controller reports a NACK say for the 2nd byte of a 5-byte-message, the transfer supposed to continue, right? (Hmm, maybe the framework handle this and restarts the transfer with I2C_M_NOSTART but the davinci driver doesn't seem to handle this flag?) Best regards Uwe > return -EREMOTEIO; > } > return -EIO; -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- 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
