[PATCH 7/7] can: m_can: workaround for transmit data less than 4 bytes
From: Dong Aisheng <hidden>
Date: 2014-10-29 10:45:27
Also in:
linux-can, netdev
Subsystem:
can network drivers, mcan device driver, the rest · Maintainers:
Marc Kleine-Budde, Vincent Mailhol, Markus Schneider-Pargmann, Linus Torvalds
We meet an IC issue that we have to write the full 8 bytes (whatever value for the second word) in Message RAM to avoid bit error for transmit data less than 4 bytes. Without the workaround, we can easily see the following errors: root at imx6qdlsolo:~# ip link set can0 up type can bitrate 1000000 [ 66.882520] IPv6: ADDRCONF(NETDEV_CHANGE): can0: link becomes ready root at imx6qdlsolo:~# cansend can0 123#112233 [ 66.935640] m_can 20e8000.can can0: Bit Error Uncorrected Signed-off-by: Dong Aisheng <redacted> --- drivers/net/can/m_can/m_can.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 219e0e3..f2d9ebe 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c@@ -1058,10 +1058,19 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff *skb, m_can_fifo_write(priv, 0, M_CAN_FIFO_ID, id); m_can_fifo_write(priv, 0, M_CAN_FIFO_DLC, can_len2dlc(cf->len) << 16); - for (i = 0; i < cf->len; i += 4) + for (i = 0; i < cf->len; i += 4) { m_can_fifo_write(priv, 0, M_CAN_FIFO_DATA(i / 4), *(u32 *)(cf->data + i)); + /* FIXME: we meet an IC issue that we have to write the full 8 + * bytes (whatever value for the second word) in Message RAM to + * avoid bit error for transmit data less than 4 bytes + */ + if (cf->len <= 4) + m_can_fifo_write(priv, 0, M_CAN_FIFO_DATA(i / 4 + 1), + 0x0); + } + can_put_echo_skb(skb, dev, 0); if (priv->can.ctrlmode & CAN_CTRLMODE_FD) {
--
1.9.1