On Fri, 13 Jan 2012, Paul Walmsley wrote: > Let's work out this formula for 115.2kbps: > > (1000000 * 16) / (1000 * 115200 / 8) > > = 16000000 / 14400000 > > = 1.11... (presumably the unit here is milliseconds) > > = 1 (since up->calc_latency is a u32) > > Then up->calc_latency is passed to pm_qos_update_request(). According to > Documentation/power/pm_qos_interface.txt, it is expecting microseconds. > So that's one problem. To fix that it should be > > up->calc_latency = (1000000 * up->port.fifosize) / > (baud / 8); > > With that change, it should be possible to enter C3, with the timings that > are in the mainline cpuidle34xx.c. Actually, just noticed that the fifosize is 60 bytes. So that's even better. With the fixed formula above, it should be ~ 5.2 ms wakeup latency - enough to enter C4 in the CPUIdle data in mainline -- at least in theory... - Paul -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
