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can: mcp251x: avoid repeated frame bug

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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>
This commit is contained in:
Benoît Locher 2012-08-27 15:02:45 +02:00 committed by Marc Kleine-Budde
parent 5002200599
commit cab32f39dc
1 changed files with 10 additions and 1 deletions
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11
drivers/net/can/mcp251x.c
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@ -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,