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can: mcp251x: write intf only when needed

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This patch introduces a variable "clear_intf" that hold the bits that
should be cleared. Only read-modify-write register if "clear_intf"
is set.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Acked-by: Wolfgang Grandegger <wg@grandegger.com>
This commit is contained in:
Marc Kleine-Budde 2010-09-28 10:18:34 +02:00
parent 7e15de3a73
commit d3cd156575
1 changed files with 13 additions and 2 deletions
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15
drivers/net/can/mcp251x.c
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@ -125,6 +125,8 @@
# define CANINTF_TX0IF 0x04
# define CANINTF_RX1IF 0x02
# define CANINTF_RX0IF 0x01
# define CANINTF_ERR_TX \
(CANINTF_ERRIF | CANINTF_TX2IF | CANINTF_TX1IF | CANINTF_TX0IF)
#define EFLG 0x2d
# define EFLG_EWARN 0x01
# define EFLG_RXWAR 0x02
@ -769,10 +771,12 @@ static irqreturn_t mcp251x_can_ist(int irq, void *dev_id)
while (!priv->force_quit) {
enum can_state new_state;
u8 intf, eflag;
u8 clear_intf = 0;
int can_id = 0, data1 = 0;
mcp251x_read_2regs(spi, CANINTF, &intf, &eflag);
/* receive buffer 0 */
if (intf & CANINTF_RX0IF) {
mcp251x_hw_rx(spi, 0);
/* Free one buffer ASAP */
@ -780,10 +784,17 @@ static irqreturn_t mcp251x_can_ist(int irq, void *dev_id)
0x00);
}
if (intf & CANINTF_RX1IF)
/* receive buffer 1 */
if (intf & CANINTF_RX1IF) {
mcp251x_hw_rx(spi, 1);
clear_intf |= CANINTF_RX1IF;
}
mcp251x_write_bits(spi, CANINTF, intf, 0x00);
/* any error or tx interrupt we need to clear? */
if (intf & CANINTF_ERR_TX)
clear_intf |= intf & CANINTF_ERR_TX;
if (clear_intf)
mcp251x_write_bits(spi, CANINTF, clear_intf, 0x00);
if (eflag)
mcp251x_write_bits(spi, EFLG, eflag, 0x00);