[PATCH v2] can: gs_usb: gs_can_open(): always configure bitrates before starting device

[Marc Kleine-Budde]

So far the driver populated the struct can_priv::do_set_bittiming() and
struct can_priv::fd::do_set_data_bittiming() callbacks.

Before bringing up the interface, user space has to configure the bitrates.
With these callbacks the configuration is directly forwarded into the CAN
hardware. Then the interface can be brought up.

An ifdown-ifup cycle (without changing the bit rates) doesn't re-configure
the bitrates in the CAN hardware. This leads to a problem with the
CANable-2.5 [1] firmware, which resets the configured bit rates during
ifdown.

To fix the problem remove both bit timing callbacks and always configure
the bitrates in the struct net_device_ops::ndo_open() callback.

[1] https://github.com/Elmue/CANable-2.5-firmware-Slcan-and-Candlelight

Cc: stable@xxxxxxxxxxxxxxx
Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices")
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
---
Changes in v2:
- fix format string
- Link to v1: https://patch.msgid.link/20260218-gs_usb-always-configure-bitrates-v1-1-6b4e0970b18a@xxxxxxxxxxxxxx
---
 drivers/net/can/usb/gs_usb.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c
index d8b2dd74b3a1..6faa877d33ae 100644
--- a/drivers/net/can/usb/gs_usb.c
+++ b/drivers/net/can/usb/gs_usb.c
@@ -772,9 +772,8 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
 	}
 }
 
-static int gs_usb_set_bittiming(struct net_device *netdev)
+static int gs_usb_set_bittiming(struct gs_can *dev)
 {
-	struct gs_can *dev = netdev_priv(netdev);
 	struct can_bittiming *bt = &dev->can.bittiming;
 	struct gs_device_bittiming dbt = {
 		.prop_seg = cpu_to_le32(bt->prop_seg),
@@ -791,9 +790,8 @@ static int gs_usb_set_bittiming(struct net_device *netdev)
 				    GFP_KERNEL);
 }
 
-static int gs_usb_set_data_bittiming(struct net_device *netdev)
+static int gs_usb_set_data_bittiming(struct gs_can *dev)
 {
-	struct gs_can *dev = netdev_priv(netdev);
 	struct can_bittiming *bt = &dev->can.fd.data_bittiming;
 	struct gs_device_bittiming dbt = {
 		.prop_seg = cpu_to_le32(bt->prop_seg),
@@ -1057,6 +1055,20 @@ static int gs_can_open(struct net_device *netdev)
 	if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP)
 		flags |= GS_CAN_MODE_HW_TIMESTAMP;
 
+	rc = gs_usb_set_bittiming(dev);
+	if (rc) {
+		netdev_err(netdev, "failed to set bittiming: %pe\n", ERR_PTR(rc));
+		goto out_usb_kill_anchored_urbs;
+	}
+
+	if (ctrlmode & CAN_CTRLMODE_FD) {
+		rc = gs_usb_set_data_bittiming(dev);
+		if (rc) {
+			netdev_err(netdev, "failed to set data bittiming: %pe\n", ERR_PTR(rc));
+			goto out_usb_kill_anchored_urbs;
+		}
+	}
+
 	/* finally start device */
 	dev->can.state = CAN_STATE_ERROR_ACTIVE;
 	dm.flags = cpu_to_le32(flags);
@@ -1370,7 +1382,6 @@ static struct gs_can *gs_make_candev(unsigned int channel,
 	dev->can.state = CAN_STATE_STOPPED;
 	dev->can.clock.freq = le32_to_cpu(bt_const.fclk_can);
 	dev->can.bittiming_const = &dev->bt_const;
-	dev->can.do_set_bittiming = gs_usb_set_bittiming;
 
 	dev->can.ctrlmode_supported = CAN_CTRLMODE_CC_LEN8_DLC;
 
@@ -1394,7 +1405,6 @@ static struct gs_can *gs_make_candev(unsigned int channel,
 		 * GS_CAN_FEATURE_BT_CONST_EXT is set.
 		 */
 		dev->can.fd.data_bittiming_const = &dev->bt_const;
-		dev->can.fd.do_set_data_bittiming = gs_usb_set_data_bittiming;
 	}
 
 	if (feature & GS_CAN_FEATURE_TERMINATION) {

---
base-commit: 77c5e3fdd2793f478e6fdae55c9ea85b21d06f8f
change-id: 20260218-gs_usb-always-configure-bitrates-bc2afb3029b6

Best regards,
--  
Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>