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> --- 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); } static void mxs_i2c_dma_finish(struct mxs_i2c_dev *i2c) -- 1.8.1.2 -- 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
