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serial: 8250_uniphier: avoid locking for FCR register write

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The hardware book says, the FCR is combined with a register called
CHAR (it will trigger interrupt when a specific character is
received).  At first, I used lock/read/modify/write/unlock dance for
the FCR to not affect the upper bits, but the CHAR is actually never
used.  It should not hurt to always clear the CHAR and to handle the
FCR as a normal case.  It can save the costly locking.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Suggested-by: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Masahiro Yamada 2016-10-24 17:00:30 +09:00 committed by Greg Kroah-Hartman
parent 94cbb6978b
commit da7fa058a3
1 changed files with 2 additions and 2 deletions
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4
drivers/tty/serial/8250/8250_uniphier.c
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@ -101,7 +101,7 @@ static unsigned int uniphier_serial_in(struct uart_port *p, int offset)
static void uniphier_serial_out(struct uart_port *p, int offset, int value)
{
unsigned int valshift = 0;
bool normal = false;
bool normal = true;
switch (offset) {
case UART_FCR:
@ -114,9 +114,9 @@ static void uniphier_serial_out(struct uart_port *p, int offset, int value)
/* fall through */
case UART_MCR:
offset = UNIPHIER_UART_LCR_MCR;
normal = false;
break;
default:
normal = true;
offset <<= UNIPHIER_UART_REGSHIFT;
break;
}