| From cab32f39dcc5b35db96497dc0a026b5dea76e4e7 Mon Sep 17 00:00:00 2001 |
| From: Benoît Locher <Benoit.Locher@skf.com> |
| Date: Mon, 27 Aug 2012 15:02:45 +0200 |
| Subject: can: mcp251x: avoid repeated frame bug |
| |
| From: Benoît Locher <Benoit.Locher@skf.com> |
| |
| 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 <Benoit.Locher@skf.com> |
| Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/net/can/mcp251x.c | 11 ++++++++++- |
| 1 file changed, 10 insertions(+), 1 deletion(-) |
| |
| --- 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 s |
| 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_dev |
| 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, |
