From: Sascha Hauer <s.hauer@pengutronix.de>
Date: Tue, 28 Sep 2010 08:00:47 +0000 (+0200)
Subject: can: mcp251x: read-modify-write eflag only when needed
X-Git-Tag: v2.6.37-rc1~147^2~100^2~4
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=7e15de3a73899903f33975b1ce57cf59c616d1d9;p=linux.git

can: mcp251x: read-modify-write eflag only when needed

Use read-modify-write instead of a simple write to change the register
contents, to close existing the race window between the original manual
read and write.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Acked-by: Wolfgang Grandegger <wg@grandegger.com>
---

diff --git a/drivers/net/can/mcp251x.c b/drivers/net/can/mcp251x.c
index 9b3466aed06d..7e2f951002a5 100644
--- a/drivers/net/can/mcp251x.c
+++ b/drivers/net/can/mcp251x.c
@@ -785,7 +785,8 @@ static irqreturn_t mcp251x_can_ist(int irq, void *dev_id)
 
 		mcp251x_write_bits(spi, CANINTF, intf, 0x00);
 
-		mcp251x_write_reg(spi, EFLG, 0x00);
+		if (eflag)
+			mcp251x_write_bits(spi, EFLG, eflag, 0x00);
 
 		/* Update can state */
 		if (eflag & EFLG_TXBO) {