From: Grant Likely <grant.likely@secretlab.ca>
To: linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, jacmet@sunsite.dk
Subject: [PATCH] Uartlite: speed up console output
Date: Sun, 21 Oct 2007 17:02:55 -0600 [thread overview]
Message-ID: <20071021230255.7066.64565.stgit@trillian.cg.shawcable.net> (raw)
From: Grant Likely <grant.likely@secretlab.ca>
Change the wait_tx routine to call cpu_relax() instead of udelay() to
reduce console output latency and test for the TXFULL bit instead of
TXEMPTY. That way the FIFO doesn't need to by 100% flushed before
writing the next character.
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
---
drivers/serial/uartlite.c | 10 ++++++----
1 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/serial/uartlite.c b/drivers/serial/uartlite.c
index dfef83f..a85f2d3 100644
--- a/drivers/serial/uartlite.c
+++ b/drivers/serial/uartlite.c
@@ -329,12 +329,14 @@ static struct uart_ops ulite_ops = {
static void ulite_console_wait_tx(struct uart_port *port)
{
int i;
+ u8 val;
- /* wait up to 10ms for the character(s) to be sent */
- for (i = 0; i < 10000; i++) {
- if (readb(port->membase + ULITE_STATUS) & ULITE_STATUS_TXEMPTY)
+ /* Spin waiting for TX fifo to have space available */
+ for (i = 0; i < 100000; i++) {
+ val = readb(port->membase + ULITE_STATUS);
+ if ((val & ULITE_STATUS_TXFULL) == 0)
break;
- udelay(1);
+ cpu_relax();
}
}
reply other threads:[~2007-10-21 23:03 UTC|newest]
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