On Tue, Jul 02, 2013 at 01:01:00PM -0300, Fabio Estevam wrote: > According to mx23 erratum 2727: > > "2727 : I2C 9th Clock Pulse (ACK) not generated when RETAIN_CLOCK set. > > Description: > > When RETAIN_CLOCK is set, the ninth clock pulse (ACK) is not generated. > However, the SDA line is read at the proper timing interval. If > RETAIN_CLOCK is cleared, the ninth clock pulse is generated. > Also, the HW_I2C_VERSION register incorrectly states the version is 1.2. > It should be 1.3. > > Workaround: > HW_I2C_CTRL1[ACK_MODE] has default value of 0. It should be set to 1 to > enable the fix for this issue." > > It has also been noticed that mx28 needs to implement this fix in order to have > SMBus to work properly. > > Reported-by: Christoph Baumann <cb@xxxxxxx> > Signed-off-by: Fabio Estevam <fabio.estevam@xxxxxxxxxxxxx> Did you see this making the driver handle some situations that caused failure before? > --- > drivers/i2c/busses/i2c-mxs.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c > index 6d8094d..ce7ac86 100644 > --- a/drivers/i2c/busses/i2c-mxs.c > +++ b/drivers/i2c/busses/i2c-mxs.c > @@ -56,6 +56,7 @@ > #define MXS_I2C_CTRL1_CLR (0x48) > > #define MXS_I2C_CTRL1_CLR_GOT_A_NAK 0x10000000 > +#define MXS_I2C_CTRL1_ACK_MODE 0x08000000 > #define MXS_I2C_CTRL1_BUS_FREE_IRQ 0x80 > #define MXS_I2C_CTRL1_DATA_ENGINE_CMPLT_IRQ 0x40 > #define MXS_I2C_CTRL1_NO_SLAVE_ACK_IRQ 0x20 > @@ -140,6 +141,14 @@ static void mxs_i2c_reset(struct mxs_i2c_dev *i2c) > writel(0x00300030, i2c->regs + MXS_I2C_TIMING2); > > writel(MXS_I2C_IRQ_MASK << 8, i2c->regs + MXS_I2C_CTRL1_SET); > + > + /* > + * According to mx23 erratum 2727: > + * "I2C 9th Clock Pulse (ACK) not generated when RETAIN_CLOCK set" > + * > + * HW_I2C_CTRL1[ACK_MODE] needs to be set when RETAIN_CLOCK is set. > + */ > + writel(MXS_I2C_CTRL1_ACK_MODE, i2c->regs + MXS_I2C_CTRL1_SET); So you set this bis in the reset routine. The first thing in mxs_i2c_pio_setup_xfer is however: writel(MXS_I2C_IRQ_MASK << 8, i2c->regs + MXS_I2C_CTRL1_CLR); which unsets the ACK_MODE bit. Also when reading the docs I couldn't find out the motivation to set RETAIN_CLOCK at all in the select command. Best regards Uwe -- 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
