linux-kernel - [PATCH 3/9] Blackfin Serial Driver: use barrier instead of cpu

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Message-Id: <1224179047-13073-4-git-send-email-cooloney@kernel.org>
Date:	Fri, 17 Oct 2008 01:44:01 +0800
From:	Bryan Wu <cooloney@...nel.org>
To:	alan@...hat.com
Cc:	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	Graf Yang <graf.yang@...log.com>,
	Bryan Wu <cooloney@...nel.org>
Subject: [PATCH 3/9] Blackfin Serial Driver: use barrier instead of cpu_relax for Blackfin SMP like patch

From: Graf Yang <graf.yang@...log.com>

We are making a SMP like patch to blackfin, cpu_relax() is replaced by a
data cache flush function which will count it to a per-cpu counter.
If this serial function is called too early, the per-cpu data area have
not been initialized, this call will cause crash.
So we'd like to use barrier() instead of cpu_relax().

Signed-off-by: Graf Yang <graf.yang@...log.com>
Signed-off-by: Bryan Wu <cooloney@...nel.org>
---
 drivers/serial/bfin_5xx.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/serial/bfin_5xx.c b/drivers/serial/bfin_5xx.c
index 16b891e..aea3a53 100644
--- a/drivers/serial/bfin_5xx.c
+++ b/drivers/serial/bfin_5xx.c
@@ -1107,7 +1107,8 @@ static __init void early_serial_putc(struct uart_port *port, int ch)
 	struct bfin_serial_port *uart = (struct bfin_serial_port *)port;
 
 	while ((!(UART_GET_LSR(uart) & THRE)) && --timeout)
-		cpu_relax();
+		barrier();
+
 	UART_PUT_CHAR(uart, ch);
 }
 
-- 
1.5.6

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