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Message-ID: <20090324140313.12735.24344.stgit@localhost.localdomain>
Date: Tue, 24 Mar 2009 14:03:16 +0000
From: Alan Cox <alan@...rguk.ukuu.org.uk>
To: linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
torvalds@...ux-foundation.org
Subject: [PATCH 09/30] blackfin: Explain why we cannot cpu_relax() in early
serial code
From: Mike Frysinger <vapier.adi@...il.com>
Signed-off-by: Mike Frysinger <vapier.adi@...il.com>
Signed-off-by: Bryan Wu <cooloney@...nel.org>
Signed-off-by: Alan Cox <alan@...rguk.ukuu.org.uk>
---
drivers/serial/bfin_5xx.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/drivers/serial/bfin_5xx.c b/drivers/serial/bfin_5xx.c
index d46d764..c7c0c1b 100644
--- a/drivers/serial/bfin_5xx.c
+++ b/drivers/serial/bfin_5xx.c
@@ -1127,6 +1127,10 @@ static __init void early_serial_putc(struct uart_port *port, int ch)
unsigned timeout = 0xffff;
struct bfin_serial_port *uart = (struct bfin_serial_port *)port;
+ /* We cannot cpu_relax() here as doing so on the BF561 relies
+ * on the per-cpu region being setup, and since this is early
+ * serial code, it may not yet be usable ...
+ */
while ((!(UART_GET_LSR(uart) & THRE)) && --timeout)
barrier();
--
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