From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751521AbXJUXFC (ORCPT ); Sun, 21 Oct 2007 19:05:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750937AbXJUXEy (ORCPT ); Sun, 21 Oct 2007 19:04:54 -0400 Received: from idcmail-mo1so.shaw.ca ([24.71.223.10]:15823 "EHLO pd4mo1so.prod.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750872AbXJUXEx (ORCPT ); Sun, 21 Oct 2007 19:04:53 -0400 Date: Sun, 21 Oct 2007 17:02:55 -0600 From: Grant Likely Subject: [PATCH] Uartlite: speed up console output To: linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, jacmet@sunsite.dk Message-id: <20071021230255.7066.64565.stgit@trillian.cg.shawcable.net> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-transfer-encoding: 7bit User-Agent: StGIT/0.12.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Grant Likely 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 --- 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(); } }