[PATCH 06/18] Blackfin Serial Driver: explain why we cannot cpu_relax() in early serial code

[Bryan Wu]

From: Mike Frysinger <vapier.adi@xxxxxxxxx>

Signed-off-by: Mike Frysinger <vapier.adi@xxxxxxxxx>
Signed-off-by: Bryan Wu <cooloney@xxxxxxxxxx>
---
 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 5a163f6..de8709d 100644
--- a/drivers/serial/bfin_5xx.c
+++ b/drivers/serial/bfin_5xx.c
@@ -1190,6 +1190,10 @@ 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();
 
-- 
1.5.6.3
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