[PATCH v3] can: m_can: initialize spin lock on device probe

[Antonios Salios <antonios@mwa.re>]

The spin lock tx_handling_spinlock in struct m_can_classdev is not being
initialized. This leads the following spinlock bad magic complaint from the
kernel, eg. when trying to send CAN frames with cansend from can-utils:

[   10.631450] BUG: spinlock bad magic on CPU#0, cansend/95
[   10.631462]  lock: 0xff60000002ec1010, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
[   10.631479] CPU: 0 UID: 0 PID: 95 Comm: cansend Not tainted 6.15.0-rc3-00032-ga79be02bba5c #5 NONE
[   10.631487] Hardware name: MachineWare SIM-V (DT)
[   10.631490] Call Trace:
[   10.631493] [<ffffffff800133e0>] dump_backtrace+0x1c/0x24
[   10.631503] [<ffffffff800022f2>] show_stack+0x28/0x34
[   10.631510] [<ffffffff8000de3e>] dump_stack_lvl+0x4a/0x68
[   10.631518] [<ffffffff8000de70>] dump_stack+0x14/0x1c
[   10.631526] [<ffffffff80003134>] spin_dump+0x62/0x6e
[   10.631534] [<ffffffff800883ba>] do_raw_spin_lock+0xd0/0x142
[   10.631542] [<ffffffff807a6fcc>] _raw_spin_lock_irqsave+0x20/0x2c
[   10.631554] [<ffffffff80536dba>] m_can_start_xmit+0x90/0x34a
[   10.631567] [<ffffffff806148b0>] dev_hard_start_xmit+0xa6/0xee
[   10.631577] [<ffffffff8065b730>] sch_direct_xmit+0x114/0x292
[   10.631586] [<ffffffff80614e2a>] __dev_queue_xmit+0x3b0/0xaa8
[   10.631596] [<ffffffff8073b8fa>] can_send+0xc6/0x242
[   10.631604] [<ffffffff8073d1c0>] raw_sendmsg+0x1a8/0x36c
[   10.631612] [<ffffffff805ebf06>] sock_write_iter+0x9a/0xee
[   10.631623] [<ffffffff801d06ea>] vfs_write+0x184/0x3a6
[   10.631633] [<ffffffff801d0a88>] ksys_write+0xa0/0xc0
[   10.631643] [<ffffffff801d0abc>] __riscv_sys_write+0x14/0x1c
[   10.631654] [<ffffffff8079ebf8>] do_trap_ecall_u+0x168/0x212
[   10.631662] [<ffffffff807a830a>] handle_exception+0x146/0x152

Initializing the spin lock in m_can_class_allocate_dev solves that
problem.

Fixes: 1fa80e23c150 ("can: m_can: Introduce a tx_fifo_in_flight counter")

Signed-off-by: Antonios Salios <antonios@mwa.re>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
---
Changes since v2:
 * Clarify bug in commit message

Changes since v1:
 * Move spin_lock_init from device probe functions to classdev alloc function
 * Add a fixes tag
---
 drivers/net/can/m_can/m_can.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 884a6352c..12e313998 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -2379,6 +2379,8 @@ struct m_can_classdev *m_can_class_allocate_dev(struct device *dev,
 	SET_NETDEV_DEV(net_dev, dev);
 
 	m_can_of_parse_mram(class_dev, mram_config_vals);
+
+	spin_lock_init(&class_dev->tx_handling_spinlock);
 out:
 	return class_dev;
 }
-- 
2.49.0