With CONFIG_DEBUG_SPINLOCK enabled we see:
BUG: spinlock bad magic on CPU#0, swapper/0
lock: early_console_dev+0x8/0x160, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
CPU: 0 PID: 0 Comm: swapper Not tainted 3.17.0-09733-gb446b33-dirty #18
diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 4b6c783..8ab27c9 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -973,6 +973,8 @@ msm_serial_early_console_setup(struct earlycon_device *device, const char *opt)
if (!device->port.membase)
return -ENODEV;
+ spin_lock_init(&device->port.lock);
+
device->con->write = msm_serial_early_write;
return 0;
}
@@ -995,6 +997,8 @@ msm_serial_early_console_setup_dm(struct earlycon_device *device,
if (!device->port.membase)
return -ENODEV;
+ spin_lock_init(&device->port.lock);
+
device->con->write = msm_serial_early_write_dm;
return 0;
}