[U-Boot] Odd value for I2C_TIMEOUT in fsl_i2c.c

Timur Tabi
2009-09-03T15:22:06Z

Currently we define I2C_TIMEOUT like this:

#define I2C_TIMEOUT (CONFIG_SYS_HZ / 4)

I'm seeing some I2C instability on a new board I'm working on, especially with SPD. If I change the above to

#define I2C_TIMEOUT (CONFIG_SYS_HZ / 2)

The problems go away (or at least, so far appear to). Can someone tell me why we choose (CONFIG_SYS_HZ / 4) to begin with? The way we use I2C_TIMEOUT is confusing:

while (readb(&i2c_dev[i2c_bus_num]->sr) & I2C_SR_MBB) {
if ((get_ticks() - timeval) > usec2ticks(I2C_TIMEOUT))
return -1;
}

CONFIG_HZ is 1000, so I2C_TIMEOUT is equal to 250. However, the way it's used, 250 isn't the number of ticks per second, it's used as number of microseconds. If CONFIG_HZ is changed to 100, does that mean that we want to call usec2ticks(25)?

I think what we should be doing is this:

#define I2C_TIMEOUT 1000

Surely, one millisecond is not too long of a timeout?

--
Timur Tabi
Linux kernel developer at Freescale