Since commit 50ea5449c563 ("can: mcp251xfd: fix ring configuration when switching from CAN-CC to CAN-FD mode"), the current ring and coalescing configuration is passed to can_ram_get_layout(). That fixed the issue when switching between CAN-CC and CAN-FD mode with configured ring (rx, tx) and/or coalescing parameters (rx-frames-irq, tx-frames-irq).

However 50ea5449c563 ("can: mcp251xfd: fix ring configuration when switching from CAN-CC to CAN-FD mode"), introduced a regression when switching CAN modes with disabled coalescing configuration: Even if the previous CAN mode has no coalescing configured, the new mode is configured with active coalescing. This leads to delayed receiving of CAN-FD frames.

This comes from the fact, that ethtool uses usecs = 0 and max_frames = 1 to disable coalescing, however the driver uses internally priv->{rx,tx}_obj_num_coalesce_irq = 0 to indicate disabled coalescing.

Fix the regression by assigning struct ethtool_coalesce ec->{rx,tx}_max_coalesced_frames_irq = 1 if coalescing is disabled in the driver as can_ram_get_layout() expects this.

Reported-by: https://github.com/vdh-robothania Closes: https://github.com/raspberrypi/linux/issues/6407 Fixes: 50ea5449c563 ("can: mcp251xfd: fix ring configuration when switching from CAN-CC to CAN-FD mode") Cc: stable@vger.kernel.org Reviewed-by: Simon Horman horms@kernel.org Link: https://patch.msgid.link/20241025-mcp251xfd-fix-coalesing-v1-1-9d11416de1df@... Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de --- drivers/net/can/spi/mcp251xfd/mcp251xfd-ring.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-ring.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-ring.c index e684991fa391..7209a831f0f2 100644 --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-ring.c +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-ring.c @@ -2,7 +2,7 @@ // // mcp251xfd - Microchip MCP251xFD Family CAN controller driver // -// Copyright (c) 2019, 2020, 2021 Pengutronix, +// Copyright (c) 2019, 2020, 2021, 2024 Pengutronix, // Marc Kleine-Budde kernel@pengutronix.de // // Based on: @@ -483,9 +483,11 @@ int mcp251xfd_ring_alloc(struct mcp251xfd_priv *priv) }; const struct ethtool_coalesce ec = { .rx_coalesce_usecs_irq = priv->rx_coalesce_usecs_irq, - .rx_max_coalesced_frames_irq = priv->rx_obj_num_coalesce_irq, + .rx_max_coalesced_frames_irq = priv->rx_obj_num_coalesce_irq == 0 ? + 1 : priv->rx_obj_num_coalesce_irq, .tx_coalesce_usecs_irq = priv->tx_coalesce_usecs_irq, - .tx_max_coalesced_frames_irq = priv->tx_obj_num_coalesce_irq, + .tx_max_coalesced_frames_irq = priv->tx_obj_num_coalesce_irq == 0 ? + 1 : priv->tx_obj_num_coalesce_irq, }; struct can_ram_layout layout;