[PATCH v2 3/3] tty: serial: omap-serial: wakeup latency constraint is in microseconds, not milliseconds
From: Govindraj <hidden>
Date: 2012-01-27 07:19:51
Also in:
linux-omap, linux-serial
On Thu, Jan 26, 2012 at 8:20 AM, Paul Walmsley [off-list ref] 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@pwsan.com> Cc: Kevin Hilman <redacted> Cc: Govindraj.R <redacted> Cc: Tomi Valkeinen <redacted> Cc: Alan Cox <redacted> Cc: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Govindraj.R <redacted>
quoted hunk ↗ jump to hunk
--- ?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 at vger.kernel.org More majordomo info at ?http://vger.kernel.org/majordomo-info.html