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authorBenoît Locher <Benoit.Locher@skf.com>2012-08-27 15:02:45 +0200
committerMarc Kleine-Budde <mkl@pengutronix.de>2012-09-03 20:12:06 +0200
commitcab32f39dcc5b35db96497dc0a026b5dea76e4e7 (patch)
tree152fdbb7d108c3e7946bf804c68f85cc204b4b2a /drivers/net/can
parent5002200599429e83fc13e0d9a2d4788b79515b0c (diff)
downloadlinux-cab32f39dcc5b35db96497dc0a026b5dea76e4e7.tar.bz2
can: mcp251x: avoid repeated frame bug
The MCP2515 has a silicon bug causing repeated frame transmission, see section 5 of MCP2515 Rev. B Silicon Errata Revision G (March 2007). Basically, setting TXBnCTRL.TXREQ in either SPI mode (00 or 11) will eventually cause the bug. The workaround proposed by Microchip is to use mode 00 and send a RTS command on the SPI bus to initiate the transmission. Cc: <stable@vger.kernel.org> Signed-off-by: Benoît Locher <Benoit.Locher@skf.com> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Diffstat (limited to 'drivers/net/can')
-rw-r--r--drivers/net/can/mcp251x.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/drivers/net/can/mcp251x.c b/drivers/net/can/mcp251x.c
index a580db29e503..26e7129332ab 100644
--- a/drivers/net/can/mcp251x.c
+++ b/drivers/net/can/mcp251x.c
@@ -83,6 +83,11 @@
#define INSTRUCTION_LOAD_TXB(n) (0x40 + 2 * (n))
#define INSTRUCTION_READ_RXB(n) (((n) == 0) ? 0x90 : 0x94)
#define INSTRUCTION_RESET 0xC0
+#define RTS_TXB0 0x01
+#define RTS_TXB1 0x02
+#define RTS_TXB2 0x04
+#define INSTRUCTION_RTS(n) (0x80 | ((n) & 0x07))
+
/* MPC251x registers */
#define CANSTAT 0x0e
@@ -397,6 +402,7 @@ static void mcp251x_hw_tx_frame(struct spi_device *spi, u8 *buf,
static void mcp251x_hw_tx(struct spi_device *spi, struct can_frame *frame,
int tx_buf_idx)
{
+ struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);
u32 sid, eid, exide, rtr;
u8 buf[SPI_TRANSFER_BUF_LEN];
@@ -418,7 +424,10 @@ static void mcp251x_hw_tx(struct spi_device *spi, struct can_frame *frame,
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);
+
+ /* use INSTRUCTION_RTS, to avoid "repeated frame problem" */
+ priv->spi_tx_buf[0] = INSTRUCTION_RTS(1 << tx_buf_idx);
+ mcp251x_spi_trans(priv->spi, 1);
}
static void mcp251x_hw_rx_frame(struct spi_device *spi, u8 *buf,