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Subject[PATCH 3.5 63/64] can: flexcan: flexcan_chip_start: fix regression, mark one MB for TX and abort pending TX
Date
3.5.7.24 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Kleine-Budde <mkl@pengutronix.de>

commit d5a7b406c529e4595ce03dc8f6dcf7fa36f106fa upstream.

In patch

0d1862e can: flexcan: fix flexcan_chip_start() on imx6

the loop in flexcan_chip_start() that iterates over all mailboxes after the
soft reset of the CAN core was removed. This loop put all mailboxes (even the
ones marked as reserved 1...7) into EMPTY/INACTIVE mode. On mailboxes 8...63,
this aborts any pending TX messages.

After a cold boot there is random garbage in the mailboxes, which leads to
spontaneous transmit of CAN frames during first activation. Further if the
interface was disabled with a pending message (usually due to an error
condition on the CAN bus), this message is retransmitted after enabling the
interface again.

This patch fixes the regression by:
1) Limiting the maximum number of used mailboxes to 8, 0...7 are used by the RX
FIFO, 8 is used by TX.
2) Marking the TX mailbox as EMPTY/INACTIVE, so that any pending TX of that
mailbox is aborted.

Cc: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
drivers/net/can/flexcan.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index 6a51f5c..2bf507b 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -61,7 +61,7 @@
#define FLEXCAN_MCR_BCC BIT(16)
#define FLEXCAN_MCR_LPRIO_EN BIT(13)
#define FLEXCAN_MCR_AEN BIT(12)
-#define FLEXCAN_MCR_MAXMB(x) ((x) & 0xf)
+#define FLEXCAN_MCR_MAXMB(x) ((x) & 0x1f)
#define FLEXCAN_MCR_IDAM_A (0 << 8)
#define FLEXCAN_MCR_IDAM_B (1 << 8)
#define FLEXCAN_MCR_IDAM_C (2 << 8)
@@ -701,9 +701,11 @@ static int flexcan_chip_start(struct net_device *dev)
*
*/
reg_mcr = flexcan_read(&regs->mcr);
+ reg_mcr &= ~FLEXCAN_MCR_MAXMB(0xff);
reg_mcr |= FLEXCAN_MCR_FRZ | FLEXCAN_MCR_FEN | FLEXCAN_MCR_HALT |
FLEXCAN_MCR_SUPV | FLEXCAN_MCR_WRN_EN |
- FLEXCAN_MCR_IDAM_C | FLEXCAN_MCR_SRX_DIS;
+ FLEXCAN_MCR_IDAM_C | FLEXCAN_MCR_SRX_DIS |
+ FLEXCAN_MCR_MAXMB(FLEXCAN_TX_BUF_ID);
netdev_dbg(dev, "%s: writing mcr=0x%08x", __func__, reg_mcr);
flexcan_write(reg_mcr, &regs->mcr);

@@ -733,6 +735,10 @@ static int flexcan_chip_start(struct net_device *dev)
netdev_dbg(dev, "%s: writing ctrl=0x%08x", __func__, reg_ctrl);
flexcan_write(reg_ctrl, &regs->ctrl);

+ /* Abort any pending TX, mark Mailbox as INACTIVE */
+ flexcan_write(FLEXCAN_MB_CNT_CODE(0x4),
+ &regs->cantxfg[FLEXCAN_TX_BUF_ID].can_ctrl);
+
/* acceptance mask/acceptance code (accept everything) */
flexcan_write(0x0, &regs->rxgmask);
flexcan_write(0x0, &regs->rx14mask);
--
1.8.3.2
--
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