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 <[email protected]>
> Signed-off-by: Fabio Estevam <[email protected]>
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/ |
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