From 6bbcbf22085e0b144899d6067e243dd26c0e7533 Mon Sep 17 00:00:00 2001 From: Paul Walmsley Date: Wed, 25 Jan 2012 19:50:56 -0700 Subject: [PATCH] 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 Cc: Tomi Valkeinen Cc: Alan Cox Acked-by: Govindraj.R Reviewed-by: Kevin Hilman Tested-by: Kevin Hilman Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/omap-serial.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c index 11fa15623e13..72fa783729d2 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); -- 2.20.1