staging: wfx: use threaded IRQ with SPI

Currently, the SPI implementation use a workqueue to acknowledge IRQ
while the SDIO-OOB implementation use a threaded IRQ.

The threaded also offers the advantage to allow level triggered IRQs.

Uniformize the code and use threaded IRQ in both case. Therefore, prefer
level triggered IRQs if the user does not specify it in the DT.
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200505123757.39506-7-Jerome.Pouiller@silabs.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/bus_spi.c

@@ -39,7 +39,6 @@ struct wfx_spi_priv {
 	struct spi_device *func;
 	struct wfx_dev *core;
 	struct gpio_desc *gpio_reset;
-	struct work_struct request_rx;
 	bool need_swab;
 };
 
@@ -140,21 +139,21 @@ static irqreturn_t wfx_spi_irq_handler(int irq, void *priv)
 {
 	struct wfx_spi_priv *bus = priv;
 
-	queue_work(system_highpri_wq, &bus->request_rx);
-	return IRQ_HANDLED;
-}
-
-static void wfx_spi_request_rx(struct work_struct *work)
-{
-	struct wfx_spi_priv *bus =
-		container_of(work, struct wfx_spi_priv, request_rx);
-
 	wfx_bh_request_rx(bus->core);
+	return IRQ_HANDLED;
 }
 
-static void wfx_flush_irq_work(void *w)
+static int wfx_spi_irq_subscribe(struct wfx_spi_priv *bus)
 {
-	flush_work(w);
+	u32 flags;
+
+	flags = irq_get_trigger_type(bus->func->irq);
+	if (!flags)
+		flags = IRQF_TRIGGER_HIGH;
+	flags |= IRQF_ONESHOT;
+	return devm_request_threaded_irq(&bus->func->dev, bus->func->irq, NULL,
+					 wfx_spi_irq_handler, IRQF_ONESHOT,
+					 "wfx", bus);
 }
 
 static size_t wfx_spi_align_size(void *priv, size_t size)
@@ -212,21 +211,12 @@ static int wfx_spi_probe(struct spi_device *func)
 		usleep_range(2000, 2500);
 	}
 
-	INIT_WORK(&bus->request_rx, wfx_spi_request_rx);
 	bus->core = wfx_init_common(&func->dev, &wfx_spi_pdata,
 				    &wfx_spi_hwbus_ops, bus);
 	if (!bus->core)
 		return -EIO;
 
-	ret = devm_add_action_or_reset(&func->dev, wfx_flush_irq_work,
-				       &bus->request_rx);
-	if (ret)
-		return ret;
-
-	ret = devm_request_irq(&func->dev, func->irq, wfx_spi_irq_handler,
-			       IRQF_TRIGGER_RISING, "wfx", bus);
-	if (ret)
-		return ret;
+	wfx_spi_irq_subscribe(bus);
 
 	return wfx_probe(bus->core);
 }