diff options
| author |   Paul Walmsley <paul@pwsan.com> | 2012-01-25 19:50:56 -0700 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-02-09 10:48:36 -0800 |
| commit | 197234520bd83aba2199add57a9d2678ee7f9781 (patch) | |
| tree | 8923cb1ed877f40141db03873e830df00df4840c /drivers/tty | |
| parent | tty: serial: OMAP: block idle while the UART is transferring data in PIO mode (diff) | |
| download | linux-dev-197234520bd83aba2199add57a9d2678ee7f9781.tar.xz linux-dev-197234520bd83aba2199add57a9d2678ee7f9781.zip | |
tty: serial: omap-serial: wakeup latency constraint is in microseconds, not milliseconds
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@pwsan.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Alan Cox <alan@linux.intel.com>
Acked-by: Govindraj.R <govindraj.raja@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | 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 18d13248d9ba..f80904145fd4 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); |