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authorPaul Walmsley <paul@pwsan.com>2012-01-25 19:50:56 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-02-09 10:48:36 -0800
commit197234520bd83aba2199add57a9d2678ee7f9781 (patch)
tree8923cb1ed877f40141db03873e830df00df4840c /drivers
parentbe4b0281956c5cae4f63f31f11d07625a6988766 (diff)
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')
-rw-r--r--drivers/tty/serial/omap-serial.c3
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);