[PATCH 09/30] blackfin: Explain why we cannot cpu_relax() in earlyserial code

[Alan Cox]

From: Mike Frysinger <vapier.adi@xxxxxxxxx>

Signed-off-by: Mike Frysinger <vapier.adi@xxxxxxxxx>
Signed-off-by: Bryan Wu <cooloney@xxxxxxxxxx>
Signed-off-by: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
---

 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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