The current uart_fifo_timeout() returns jiffies, which is not always
the most convenient for callers. Add a variant uart_fifo_timeout_ms()
that returns the timeout in milliseconds.
NOTES:
- msecs_to_jiffies() rounds up, unlike nsecs_to_jiffies(). This is
because msecs_to_jiffies() is actually intended for device drivers
to calculate timeout value. This means we don't need to take the max
of the timeout and "1" since the timeout will always be > 0 ms (we
add 20 ms of slop).
- uart_fifo_timeout_ms() returns "unsigned int" but we leave
uart_fifo_timeout() returning "unsigned long". This matches the
types of msecs_to_jiffies().
Suggested-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
Changes in v4:
- New
include/linux/serial_core.h | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 8cb65f50e830..97968acfd564 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -889,14 +889,21 @@ unsigned int uart_get_divisor(struct uart_port *port, unsigned int baud);
/*
* Calculates FIFO drain time.
*/
-static inline unsigned long uart_fifo_timeout(struct uart_port *port)
+static inline unsigned int uart_fifo_timeout_ms(struct uart_port *port)
{
u64 fifo_timeout = (u64)READ_ONCE(port->frame_time) * port->fifosize;
+ unsigned int fifo_timeout_ms = div_u64(fifo_timeout, NSEC_PER_MSEC);
- /* Add .02 seconds of slop */
- fifo_timeout += 20 * NSEC_PER_MSEC;
+ /*
+ * Add .02 seconds of slop. This also helps account for the fact that
+ * when we converted from ns to ms that we didn't round up.
+ */
+ return fifo_timeout_ms + 20;
+}
- return max(nsecs_to_jiffies(fifo_timeout), 1UL);
+static inline unsigned long uart_fifo_timeout(struct uart_port *port)
+{
+ return msecs_to_jiffies(uart_fifo_timeout_ms(port));
}
/* Base timer interval for polling */
--
2.45.2.505.gda0bf45e8d-goog
