From 9680ec7a46f19fd9b143adc8c69493834f450eee Mon Sep 17 00:00:00 2001 From: Benoît Locher Date: Mon, 27 Aug 2012 15:02:45 +0200 Subject: can: mcp251x: avoid repeated frame bug MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit cab32f39dcc5b35db96497dc0a026b5dea76e4e7 upstream. 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. Signed-off-by: Benoît Locher Signed-off-by: Marc Kleine-Budde Signed-off-by: Greg Kroah-Hartman --- drivers/net/can/mcp251x.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'drivers/net/can') diff --git a/drivers/net/can/mcp251x.c b/drivers/net/can/mcp251x.c index 330140ee266..9bcc39a07c4 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, -- cgit v1.2.3-18-g5258