Lars, On Sat, Mar 16, 2013 at 7:41 AM, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote: > I think you still need the mutex for serialization, otherwise the requests > would just cancel each other out. Btw. what happens if you start a conversion > while another is still in progress? Is it possible to abort a conversion? I was thinking that the spinlock would just replace the mutex for the purposes of serialization. I stepped back a bit, though, and I'm wondering if we're over-thinking things. The timeout case should certainly be handled properly (thanks for pointing it out), but getting a timeout is really not expected and adding a lot of extra overhead to handle it elegantly seems a bit much? Specifically, the mutex means that we have one user of the ADC at a time, and ADC conversion has nothing variable about it. The user manual that I have access to talks about 12-bit conversion happening in 1 microsecond with a 5MHz input clock or 5 microseconds with a 1MHz input clock. Even if someone has clocks configured very differently, it would be hard to imagine a conversion actually taking a full second. ...so that means that if the timeout actually fires then something else fairly drastic has gone wrong. It's _very_ unlikely that the IRQ will still go off for this conversion sometime in the future. To me, total modifications to what's landed already ought to be: * Change timeout to long (from unsigned long) * Make sure we return errors (negative results) from wait_for_completion_interruptible_timeout() properly. * If we get back a value of 0 from wait_for_completion_interruptible_timeout() then we should print a warning and attempt machinations to reset the ADC. Without ever seeing real-world situtations that would cause a real timeout these machinations would be a bit of a guess (is resetting the adc useful when it's more likely that someone accidentally messed with the clock tree or power gated the ADC?)... ...or perhaps a warning and a TODO in the code would be enough? Thoughts? -Doug -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
