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 ---
Changed timeout value from 100 ms to 1 ms.
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..a50a371 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 = 1000; + + /* 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;