diff options
| author | Kevin O'Connor <kevin@koconnor.net> | 2011-07-09 20:22:21 -0400 |
|---|---|---|
| committer | Patrick Georgi <patrick@georgi-clan.de> | 2011-07-12 11:36:20 +0200 |
| commit | a68555f48d06b4c8d55f7e4ca208805bec3d5512 (patch) | |
| tree | 132a21ab3f20d2ca5ce967705d4d92c3c0dbe476 /src/lib | |
| parent | 537cacfa04c9dc56cd608012a73d95ab342d2f81 (diff) | |
Do full flush on uart8250 only at end of printk.
The previous code does a full flush of the uart after every character.
Unfortunately, this can cause transmission delays on some serial
ports.
This patch changes the code so that it does a flush at the end of
every printk instead of at the end of every character. This reduces
the time it takes to transmit serial messages (up to 9% on my Asrock
e350m1 board). It also makes the transmission time more consistent
which is important when performing timing tests via serial
transmissions.
Change-Id: I6b28488b905da68c6d68d7c517cc743cde567d70
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Reviewed-on: http://review.coreboot.org/90
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)
Reviewed-by: Rudolf Marek <r.marek@assembler.cz>
Reviewed-by: Sven Schnelle <svens@stackframe.org>
Diffstat (limited to 'src/lib')
| -rw-r--r-- | src/lib/uart8250.c | 5 | ||||
| -rw-r--r-- | src/lib/uart8250mem.c | 5 |
2 files changed, 8 insertions, 2 deletions
diff --git a/src/lib/uart8250.c b/src/lib/uart8250.c index 64e8854ef5..e7ddd0bfd5 100644 --- a/src/lib/uart8250.c +++ b/src/lib/uart8250.c @@ -48,7 +48,10 @@ void uart8250_tx_byte(unsigned base_port, unsigned char data) { uart8250_wait_to_tx_byte(base_port); outb(data, base_port + UART_TBR); - /* Make certain the data clears the fifos */ +} + +void uart8250_tx_flush(unsigned base_port) +{ uart8250_wait_until_sent(base_port); } diff --git a/src/lib/uart8250mem.c b/src/lib/uart8250mem.c index 918308ecdf..e79cb63346 100644 --- a/src/lib/uart8250mem.c +++ b/src/lib/uart8250mem.c @@ -51,7 +51,10 @@ void uart8250_mem_tx_byte(unsigned base_port, unsigned char data) { uart8250_mem_wait_to_tx_byte(base_port); write8(base_port + UART_TBR, data); - /* Make certain the data clears the FIFOs */ +} + +void uart8250_mem_tx_flush(unsigned base_port) +{ uart8250_mem_wait_until_sent(base_port); } |