On 06.05.2024 15:49:18, Vitor Soares wrote:
From: Vitor Soares vitor.soares@toradex.com
When the mcp251xfd_start_xmit() function fails, the driver stops processing messages, and the interrupt routine does not return, running indefinitely even after killing the running application.
Error messages: [ 441.298819] mcp251xfd spi2.0 can0: ERROR in mcp251xfd_start_xmit: -16 [ 441.306498] mcp251xfd spi2.0 can0: Transmit Event FIFO buffer not empty. (seq=0x000017c7, tef_tail=0x000017cf, tef_head=0x000017d0, tx_head=0x000017d3). ... and repeat forever.
The issue can be triggered when multiple devices share the same SPI interface. And there is concurrent access to the bus.
The problem occurs because tx_ring->head increments even if mcp251xfd_start_xmit() fails. Consequently, the driver skips one TX package while still expecting a response in mcp251xfd_handle_tefif_one().
This patch resolves the issue by decreasing tx_ring->head and removing the skb from the echo stack if mcp251xfd_start_xmit() fails. Consequently, the package is dropped not been possible to re-transmit.
Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN") Cc: stable@vger.kernel.org Signed-off-by: Vitor Soares vitor.soares@toradex.com
With this approach, some packages get lost in concurrent SPI bus access due to can_put_echo_skb() being called before mcp251xfd_tx_obj_write(). The can_put_echo_skb() calls can_create_echo_skb() that consumes the original skb resulting in a Kernel NULL pointer dereference error if return NETDEV_TX_BUSY on mcp251xfd_tx_obj_write() failure. A potential solution would be to change the code to use spi_sync(), which would wait for SPI bus to be unlocked. Any thoughts about this?
This is not an option. I think you need a echo_skb function that does the necessary cleanup, something like:
void can_remove_echo_skb(struct net_device *dev, unsigned int idx) { struct can_priv *priv = netdev_priv(dev);
priv->echo_skb[idx] = NULL; }
I think you can open-code the "priv->echo_skb[idx] = NULL;" directly in the driver.
And you have to take care of calling netdev_completed_queue(priv->ndev, 1, frame_len);
Another option would be to start a workqueue and use spi_sync() in case the spi_async() is busy.
regards, Marc