On Thu, Jan 26, 2012 at 8:20 AM, Paul Walmsley <paul@xxxxxxxxx> wrote: > The receive FIFO wakeup latency estimate in the omap-serial driver is > three orders of magnitude too small. This effectively prevents the > MPU from going to a low-power state when CONFIG_CPU_IDLE=y. This is a > major power management regression and masks some other FIFO-related > bugs in the driver. > > Fix by correcting the most egregious problem in the RX wakeup latency > estimate. There are several other flaws in the estimator; these will > be fixed by a separate patch series intended for 3.4. > > The difference in low-power states with this patch can be observed via > debugfs in pm_debug/count. > > This estimate does not have any effect when CONFIG_CPU_IDLE=n. > > Signed-off-by: Paul Walmsley <paul@xxxxxxxxx> > Cc: Kevin Hilman <khilman@xxxxxx> > Cc: Govindraj.R <govindraj.raja@xxxxxx> > Cc: Tomi Valkeinen <tomi.valkeinen@xxxxxx> > Cc: Alan Cox <alan@xxxxxxxxxxxxxxx> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxx> Acked-by: Govindraj.R <govindraj.raja@xxxxxx> > --- > drivers/tty/serial/omap-serial.c | 3 +-- > 1 files changed, 1 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c > index 11fa156..72fa783 100644 > --- a/drivers/tty/serial/omap-serial.c > +++ b/drivers/tty/serial/omap-serial.c > @@ -740,8 +740,7 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios, > quot = serial_omap_get_divisor(port, baud); > > /* calculate wakeup latency constraint */ > - up->calc_latency = (1000000 * up->port.fifosize) / > - (1000 * baud / 8); > + up->calc_latency = (USEC_PER_SEC * up->port.fifosize) / (baud / 8); > up->latency = up->calc_latency; > schedule_work(&up->qos_work); > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-serial" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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
