[coreboot] New patch to review: 5176106 Do full flush on uart8250 only at end of printk.

[Anonymous Coward (kevin@koconnor.net)]

Anonymous Coward (kevin at koconnor.net) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/90

-gerrit

commit 51761067ec0ded3b8fa73efffc1462f262a94759
Author: Kevin O'Connor <kevin at koconnor.net>
Date:   Sat Jul 9 20:22:21 2011 -0400

    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 at koconnor.net>
---
 src/arch/x86/lib/romstage_console.c |   16 +++++++++++++---
 src/console/uart8250_console.c      |    6 ++++++
 src/include/uart8250.h              |    1 +
 src/lib/uart8250.c                  |    5 ++++-
 4 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/src/arch/x86/lib/romstage_console.c b/src/arch/x86/lib/romstage_console.c
index a5f2e2b..faa8afb 100644
--- a/src/arch/x86/lib/romstage_console.c
+++ b/src/arch/x86/lib/romstage_console.c
@@ -48,6 +48,16 @@ static void console_tx_byte(unsigned char byte)
 #endif
 }
 
+static void console_tx_flush(void)
+{
+#if CONFIG_CONSOLE_SERIAL8250
+	uart8250_tx_flush(CONFIG_TTYS0_BASE);
+#endif
+#if CONFIG_CONSOLE_NE2K
+	ne2k_transmit(CONFIG_CONSOLE_NE2K_IO_PORT);
+#endif
+}
+
 int do_printk(int msg_level, const char *fmt, ...)
 {
 	va_list args;
@@ -60,8 +70,8 @@ int do_printk(int msg_level, const char *fmt, ...)
 	va_start(args, fmt);
 	i = vtxprintf(console_tx_byte, fmt, args);
 	va_end(args);
-#if CONFIG_CONSOLE_NE2K
-	ne2k_transmit(CONFIG_CONSOLE_NE2K_IO_PORT);
-#endif
+
+	console_tx_flush();
+
 	return i;
 }
diff --git a/src/console/uart8250_console.c b/src/console/uart8250_console.c
index 4799ca6..330ed68 100644
--- a/src/console/uart8250_console.c
+++ b/src/console/uart8250_console.c
@@ -31,6 +31,11 @@ static void ttyS0_tx_byte(unsigned char data)
 	uart8250_tx_byte(CONFIG_TTYS0_BASE, data);
 }
 
+static void ttyS0_tx_flush(void)
+{
+	uart8250_tx_flush(CONFIG_TTYS0_BASE);
+}
+
 static unsigned char ttyS0_rx_byte(void)
 {
 	return uart8250_rx_byte(CONFIG_TTYS0_BASE);
@@ -44,6 +49,7 @@ static int ttyS0_tst_byte(void)
 static const struct console_driver uart8250_console __console = {
 	.init     = ttyS0_init,
 	.tx_byte  = ttyS0_tx_byte,
+	.tx_flush = ttyS0_tx_flush,
 	.rx_byte  = ttyS0_rx_byte,
 	.tst_byte = ttyS0_tst_byte,
 };
diff --git a/src/include/uart8250.h b/src/include/uart8250.h
index bbf2d8c..ee0cd39 100644
--- a/src/include/uart8250.h
+++ b/src/include/uart8250.h
@@ -131,6 +131,7 @@
 unsigned char uart8250_rx_byte(unsigned base_port);
 int uart8250_can_rx_byte(unsigned base_port);
 void uart8250_tx_byte(unsigned base_port, unsigned char data);
+void uart8250_tx_flush(unsigned base_port);
 
 /* Yes it is silly to have three different uart init functions. But we used to
  * have three different sets of uart code, so it's an improvement.
diff --git a/src/lib/uart8250.c b/src/lib/uart8250.c
index 64e8854..e7ddd0b 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);
 }