diff -uNr linux-2.6.39.1.orig/drivers/net/can/mcp251x.c linux-2.6.39.1.new/drivers/net/can/mcp251x.c
--- linux-2.6.39.1.orig/drivers/net/can/mcp251x.c	2011-06-02 20:34:20.000000000 -0400
+++ linux-2.6.39.1.new/drivers/net/can/mcp251x.c	2011-06-21 12:07:43.720708907 -0400
@@ -82,6 +82,7 @@
 #define INSTRUCTION_BIT_MODIFY	0x05
 #define INSTRUCTION_LOAD_TXB(n)	(0x40 + 2 * (n))
 #define INSTRUCTION_READ_RXB(n)	(((n) == 0) ? 0x90 : 0x94)
+#define INSTRUCTION_RTS(n)	(0x80 | (1 << n))
 #define INSTRUCTION_RESET	0xC0
 
 /* MPC251x registers */
@@ -377,6 +378,15 @@
 	mcp251x_spi_trans(spi, 4);
 }
 
+static void mcp251x_write_rts(struct spi_device *spi, int tx_buf_idx)
+{
+	struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);
+
+	priv->spi_tx_buf[0] = INSTRUCTION_RTS(tx_buf_idx);
+
+	mcp251x_spi_trans(spi, 1);
+}
+
 static void mcp251x_hw_tx_frame(struct spi_device *spi, u8 *buf,
 				int len, int tx_buf_idx)
 {
@@ -418,7 +428,7 @@
 	buf[TXBDLC_OFF] = (rtr << DLC_RTR_SHIFT) | frame->can_dlc;
 	memcpy(buf + TXBDAT_OFF, frame->data, frame->can_dlc);
 	mcp251x_hw_tx_frame(spi, buf, frame->can_dlc, tx_buf_idx);
-	mcp251x_write_reg(spi, TXBCTRL(tx_buf_idx), TXBCTRL_TXREQ);
+	mcp251x_write_rts(spi, tx_buf_idx);
 }
 
 static void mcp251x_hw_rx_frame(struct spi_device *spi, u8 *buf,