diff options
| author | Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> | 2022-04-25 17:33:58 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-04-26 14:28:32 +0300 |
| commit | 31f6bd7fad3b149a1eb6f67fc2e742e4df369b3d (patch) | |
| tree | 463107713e6683f803b96e7dcab07a1c140a6f41 | |
| parent | 070e246217230cce21b8dddad38bd59428494c48 (diff) | |
| download | linux-31f6bd7fad3b149a1eb6f67fc2e742e4df369b3d.tar.xz | |
serial: Store character timing information to uart_port
Struct uart_port currently stores FIFO timeout. Having character timing
information readily available is useful. Even serial core itself
determines char_time from port->timeout using inverse calculation.
Store frame_time directly into uart_port. Character time is stored in
nanoseconds to have reasonable precision with high rates. To avoid
overflow, 64-bit math is necessary.
It might be possible to determine timeout from frame_time by
multiplying it with fifosize as needed but only part of the users seem
to be protected by a lock. Thus, this patch does not pursue storing
only frame_time in uart_port.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220425143410.12703-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/serial/serial_core.c | 14 | ||||
| -rw-r--r-- | include/linux/serial_core.h | 1 |
2 files changed, 9 insertions, 6 deletions
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 01823ce87801..82a1770dd808 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -24,6 +24,7 @@ #include <linux/sysrq.h> #include <linux/delay.h> #include <linux/mutex.h> +#include <linux/math64.h> #include <linux/security.h> #include <linux/irq.h> @@ -338,15 +339,18 @@ void uart_update_timeout(struct uart_port *port, unsigned int cflag, unsigned int baud) { - unsigned int size; + unsigned int size = tty_get_frame_size(cflag); + u64 frame_time; - size = tty_get_frame_size(cflag) * port->fifosize; + frame_time = (u64)size * NSEC_PER_SEC; + size *= port->fifosize; /* * Figure the timeout to send the above number of bits. * Add .02 seconds of slop */ port->timeout = (HZ * size) / baud + HZ/50; + port->frame_time = DIV64_U64_ROUND_UP(frame_time, baud); } EXPORT_SYMBOL(uart_update_timeout); @@ -1643,10 +1647,8 @@ static void uart_wait_until_sent(struct tty_struct *tty, int timeout) * Note: we have to use pretty tight timings here to satisfy * the NIST-PCTS. */ - char_time = (port->timeout - HZ/50) / port->fifosize; - char_time = char_time / 5; - if (char_time == 0) - char_time = 1; + char_time = max(nsecs_to_jiffies(port->frame_time / 5), 1UL); + if (timeout && timeout < char_time) char_time = timeout; diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index d4828e69087a..cbd5070bc87f 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -232,6 +232,7 @@ 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; unsigned int custom_divisor; |