[U-Boot-Users] [PATCH 01/10] [ARM] MXC: insert bus busy check in i2c_probe

Jean-Christophe PLAGNIOL-VILLARD
2008-07-05T15:59:28Z

On 16:50 Fri 04 Jul , Jens Gehrlein wrote:
> On fast CPUs the time between two chip queries can become too short
> to issue clear start and stop conditions. The bus seems to be blocked.
> This cannot be compensated by just waiting for completed byte transfer.
> The patch introduces polling of the bus busy bit in the I2C
> controller's status register before the next bus access is possible.
>
> Signed-off-by: Jens Gehrlein <sew_s@tqs.de>
> ---
>
> drivers/i2c/mxc_i2c.c | 10 ++++++++++
> 1 files changed, 10 insertions(+), 0 deletions(-)
>
>
> diff --git a/drivers/i2c/mxc_i2c.c b/drivers/i2c/mxc_i2c.c
> index a218329..6f9306f 100644
> --- a/drivers/i2c/mxc_i2c.c
> +++ b/drivers/i2c/mxc_i2c.c
> @@ -115,6 +115,16 @@ static int rx_byte(void)
> int i2c_probe(uchar chip)
> {
> int ret;
> + int timeout = 100000;
Could you explain why 100000?
> +
> + /* Check if bus is busy before probing next chip */
> + while ((__REG16(I2C_BASE + I2SR) & I2SR_IBB) && --timeout)
> + udelay(1);
> +
> + if (timeout == 0) {
> + printf ("\nerror: bus blocked\n");
> + return -1;
> + }
>
> __REG16(I2C_BASE + I2CR) = 0; /* Reset module */
> __REG16(I2C_BASE + I2CR) = I2CR_IEN;
Best Regards,
J.