can: mcp251xfd: mcp251xfd_ring_alloc(): fix coalescing configuration when switching...

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@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-ring.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-ring.c
index e684991fa3917d4f6b6ebda8329f72971237574e..7209a831f0f2089e409c6be635f0e5dc7b2271da 100644 (file)
--- 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;