mfd: dln2: Run event handler loop under spinlock

[ Upstream commit 3d858942250820b9adc35f963a257481d6d4c81d ]

The event handler loop must be run with interrupts disabled.
Otherwise we will have a warning:

[ 1970.785649] irq 31 handler lineevent_irq_handler+0x0/0x20 enabled interrupts
[ 1970.792739] WARNING: CPU: 0 PID: 0 at kernel/irq/handle.c:159 __handle_irq_event_percpu+0x162/0x170
[ 1970.860732] RIP: 0010:__handle_irq_event_percpu+0x162/0x170
...
[ 1970.946994] Call Trace:
[ 1970.949446]  <IRQ>
[ 1970.951471]  handle_irq_event_percpu+0x2c/0x80
[ 1970.955921]  handle_irq_event+0x23/0x43
[ 1970.959766]  handle_simple_irq+0x57/0x70
[ 1970.963695]  generic_handle_irq+0x42/0x50
[ 1970.967717]  dln2_rx+0xc1/0x210 [dln2]
[ 1970.971479]  ? usb_hcd_unmap_urb_for_dma+0xa6/0x1c0
[ 1970.976362]  __usb_hcd_giveback_urb+0x77/0xe0
[ 1970.980727]  usb_giveback_urb_bh+0x8e/0xe0
[ 1970.984837]  tasklet_action_common.isra.0+0x4a/0xe0
...

Recently xHCI driver switched to tasklets in the commit 36dc01657b49
("usb: host: xhci: Support running urb giveback in tasklet context").

The handle_irq_event_* functions are expected to be called with interrupts
disabled and they rightfully complain here because we run in tasklet context
with interrupts enabled.

Use a event spinlock to protect event handler from being interrupted.

Note, that there are only two users of this GPIO and ADC drivers and both of
them are using generic_handle_irq() which makes above happen.

Fixes: 338a12814297 ("mfd: Add support for Diolan DLN-2 devices")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/mfd/dln2.c b/drivers/mfd/dln2.c
index 672831d5ee32e1c6ba0737cb99a2f80d0e867373..97a69cd6f1278c819de39f1241dfa466877b9100 100644 (file)
--- a/drivers/mfd/dln2.c
+++ b/drivers/mfd/dln2.c
@@ -294,7 +294,11 @@ static void dln2_rx(struct urb *urb)
        len = urb->actual_length - sizeof(struct dln2_header);
 
        if (handle == DLN2_HANDLE_EVENT) {
+               unsigned long flags;
+
+               spin_lock_irqsave(&dln2->event_cb_lock, flags);
                dln2_run_event_callbacks(dln2, id, echo, data, len);
+               spin_unlock_irqrestore(&dln2->event_cb_lock, flags);
        } else {
                /* URB will be re-submitted in _dln2_transfer (free_rx_slot) */
                if (dln2_transfer_complete(dln2, urb, handle, echo))