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Subject[PATCH 1/3] serial: 8250_early: optimize early 8250 uart
Date
In early 8250, IER is already zero so no point in writing this - twice
per char.

This helped improve the SystemC model based ARC OSCI platform

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Rob Herring <robh@kernel.org>
---
drivers/tty/serial/8250/8250_early.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
index 4858b8a99d3b..ce2a8abd1f54 100644
--- a/drivers/tty/serial/8250/8250_early.c
+++ b/drivers/tty/serial/8250/8250_early.c
@@ -95,13 +95,16 @@ static void __init early_serial8250_write(struct console *console,

/* Save the IER and disable interrupts */
ier = serial8250_early_in(port, UART_IER);
- serial8250_early_out(port, UART_IER, 0);
+ if (ier)
+ serial8250_early_out(port, UART_IER, 0);

uart_console_write(port, s, count, serial_putc);

/* Wait for transmitter to become empty and restore the IER */
wait_for_xmitr(port);
- serial8250_early_out(port, UART_IER, ier);
+
+ if (ier)
+ serial8250_early_out(port, UART_IER, ier);
}

static unsigned int __init probe_baud(struct uart_port *port)
--
1.8.3.2


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