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 13:28:32 +0200 |
| commit | 31f6bd7fad3b149a1eb6f67fc2e742e4df369b3d (patch) | |
| tree | 463107713e6683f803b96e7dcab07a1c140a6f41 /drivers | |
| parent | serial: 8250: dw: Improve RZN1 support (diff) | |
| download | linux-dev-31f6bd7fad3b149a1eb6f67fc2e742e4df369b3d.tar.xz linux-dev-31f6bd7fad3b149a1eb6f67fc2e742e4df369b3d.zip | |
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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/tty/serial/serial_core.c | 14 |
1 files changed, 8 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; |