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path: root/drivers/serial/8250.c
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Diffstat (limited to 'drivers/serial/8250.c')
-rw-r--r--drivers/serial/8250.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 5261f0af8b1..2964ca9df5a 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -920,12 +920,16 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
#ifdef __i386__
outb(0xff, 0x080);
#endif
- scratch2 = serial_inp(up, UART_IER);
+ /*
+ * Mask out IER[7:4] bits for test as some UARTs (e.g. TL
+ * 16C754B) allow only to modify them if an EFR bit is set.
+ */
+ scratch2 = serial_inp(up, UART_IER) & 0x0f;
serial_outp(up, UART_IER, 0x0F);
#ifdef __i386__
outb(0, 0x080);
#endif
- scratch3 = serial_inp(up, UART_IER);
+ scratch3 = serial_inp(up, UART_IER) & 0x0f;
serial_outp(up, UART_IER, scratch);
if (scratch2 != 0 || scratch3 != 0x0F) {
/*