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serial: Drop timeout from uart_port

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Since commit 31f6bd7fad ("serial: Store character timing information
to uart_port"), per frame timing information is available on uart_port.
Uart port's timeout can be derived from frame_time by multiplying with
fifosize.

Most callers of uart_poll_timeout are not made under port's lock. To be
on the safe side, make sure frame_time is only accessed once. As
fifo_size is effectively a constant, it shouldn't cause any issues.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220613113905.22962-1-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ilpo Järvinen 2022-06-13 14:39:05 +03:00 • committed by Greg Kroah-Hartman
parent ab24a01b27
commit f9008285bb
4 changed files with 27 additions and 25 deletions
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16
include/linux/serial_core.h
View file

@ -232,7 +232,6 @@ struct uart_port {
int hw_stopped; /* sw-assisted CTS flow state */
unsigned int mctrl; /* current modem ctrl settings */
unsigned int timeout; /* character-based timeout */
unsigned int frame_time; /* frame timing in ns */
unsigned int type; /* port type */
const struct uart_ops *ops;
@ -335,10 +334,23 @@ unsigned int uart_get_baud_rate(struct uart_port *port, struct ktermios *termios
unsigned int max);
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)
{
u64 fifo_timeout = (u64)READ_ONCE(port->frame_time) * port->fifosize;
/* Add .02 seconds of slop */
fifo_timeout += 20 * NSEC_PER_MSEC;
return max(nsecs_to_jiffies(fifo_timeout), 1UL);
}
/* Base timer interval for polling */
static inline int uart_poll_timeout(struct uart_port *port)
{
int timeout = port->timeout;
int timeout = uart_fifo_timeout(port);
return timeout > 6 ? (timeout / 2 - 2) : 1;
}