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Message-Id: <20120917003638.813933543@decadent.org.uk>
Date: Mon, 17 Sep 2012 01:37:56 +0100
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
alan@...rguk.ukuu.org.uk,
Benoît Locher <Benoit.Locher@....com>,
Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [ 091/135] can: mcp251x: avoid repeated frame bug
3.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Benoît Locher <Benoit.Locher@....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@....com>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
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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