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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>
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1 parent 537cacf commit a68555f48d06b4c8d55f7e4ca208805bec3d5512 @KevinOConnor KevinOConnor committed with pgeorgi Jul 10, 2011
@@ -48,6 +48,19 @@ static void console_tx_byte(unsigned char byte)
#endif
}
+static void console_tx_flush(void)
+{
+#if CONFIG_CONSOLE_SERIAL8250MEM
+ uart8250_mem_tx_flush(CONFIG_OXFORD_OXPCIE_BASE_ADDRESS + 0x1000);
+#endif
+#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 +73,8 @@ 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;
}
@@ -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,
};
@@ -36,6 +36,11 @@ static void uartmem_tx_byte(unsigned char data)
uart8250_mem_tx_byte(uart_bar, data);
}
+static void uartmem_tx_flush(void)
+{
+ uart8250_mem_tx_flush(uart_bar);
+}
+
static unsigned char uartmem_rx_byte(void)
{
if (!uart_bar)
@@ -55,6 +60,7 @@ static int uartmem_tst_byte(void)
static const struct console_driver uart8250mem_console __console = {
.init = uartmem_init,
.tx_byte = uartmem_tx_byte,
+ .tx_flush = uartmem_tx_flush,
.rx_byte = uartmem_rx_byte,
.tst_byte = uartmem_tst_byte,
};
View
@@ -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.
@@ -142,6 +143,7 @@ void uart_init(void);
unsigned char uart8250_mem_rx_byte(unsigned base_port);
int uart8250_mem_can_rx_byte(unsigned base_port);
void uart8250_mem_tx_byte(unsigned base_port, unsigned char data);
+void uart8250_mem_tx_flush(unsigned base_port);
void uart8250_mem_init(unsigned base_port, unsigned divisor);
u32 uart_mem_init(void);
View
@@ -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);
}
View
@@ -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);
}

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