[PATCH] can: mcp251x: avoid repeated frame bug
From: Marc Kleine-Budde <mkl@pengutronix.de>
Date: 2012-09-04 20:55:56
Also in:
linux-can
Subsystem:
can network drivers, the rest · Maintainers:
Marc Kleine-Budde, Vincent Mailhol, Linus Torvalds
From: Benoît Locher <redacted> 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: <redacted> Signed-off-by: Benoît Locher <redacted> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de> --- drivers/net/can/mcp251x.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/net/can/mcp251x.c b/drivers/net/can/mcp251x.c
index a580db2..26e7129 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,
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1.7.10