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From: Simon Kagstrom on 17 Mar 2010 08:40
Port 0x80 is not safe to use on all x86 boards (see
arch/x86/kernel/io_delay.c), so use native_io_delay instead.

Signed-off-by: Simon Kagstrom <simon.kagstrom(a)netinsight.net>
---
drivers/serial/8250.c | 12 +++++-------
1 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index c3db16b..b3007a4 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -38,6 +38,7 @@
#include <linux/serial_8250.h>
#include <linux/nmi.h>
#include <linux/mutex.h>
+#include <linux/io.h>

#include <asm/io.h>
#include <asm/irq.h>
@@ -1109,11 +1110,8 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
* Do a simple existence test first; if we fail this,
* there's no point trying anything else.
*
- * 0x80 is used as a nonsense port to prevent against
- * false positives due to ISA bus float. The
- * assumption is that 0x80 is a non-existent port;
- * which should be safe since include/asm/io.h also
- * makes this assumption.
+ * The IO delay is used to prevent against false positives
+ * due to ISA bus float.
*
* Note: this is safe as long as MCR bit 4 is clear
* and the device is in "PC" mode.
@@ -1121,7 +1119,7 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
scratch = serial_inp(up, UART_IER);
serial_outp(up, UART_IER, 0);
#ifdef __i386__
- outb(0xff, 0x080);
+ native_io_delay();
#endif
/*
* Mask out IER[7:4] bits for test as some UARTs (e.g. TL
@@ -1130,7 +1128,7 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
scratch2 = serial_inp(up, UART_IER) & 0x0f;
serial_outp(up, UART_IER, 0x0F);
#ifdef __i386__
- outb(0, 0x080);
+ native_io_delay();
#endif
scratch3 = serial_inp(up, UART_IER) & 0x0f;
serial_outp(up, UART_IER, scratch);
--
1.6.0.4

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Prev: [tip:perf/core] perf/core, x86: Reduce number of CONFIG_X86_LOCAL_APIC macros
Next: [PATCH 2/2]: x86 real mode: Set delay port according to kernel config