ASoC: stm32: spdifrx: fix inconsistent lock state

In current spdifrx driver locks may be requested as follows:
- request lock on iec capture control, when starting synchronization.
- request lock in interrupt context, when spdifrx stop is called
from IRQ handler.

Take lock with IRQs disabled, to avoid the possible deadlock.

Lockdep report:
[   74.278059] ================================
[   74.282306] WARNING: inconsistent lock state
[   74.290120] --------------------------------
...
[   74.314373]        CPU0
[   74.314377]        ----
[   74.314381]   lock(&(&spdifrx->lock)->rlock);
[   74.314396]   <Interrupt>
[   74.314400]     lock(&(&spdifrx->lock)->rlock);

Fixes: 03e4d5d56f ("ASoC: stm32: Add SPDIFRX support")

Signed-off-by: Olivier Moysan <olivier.moysan@st.com>
Link: https://lore.kernel.org/r/20191204154333.7152-2-olivier.moysan@st.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/stm/stm32_spdifrx.c

@@ -320,6 +320,7 @@ static void stm32_spdifrx_dma_ctrl_stop(struct stm32_spdifrx_data *spdifrx)
 static int stm32_spdifrx_start_sync(struct stm32_spdifrx_data *spdifrx)
 {
 	int cr, cr_mask, imr, ret;
+	unsigned long flags;
 
 	/* Enable IRQs */
 	imr = SPDIFRX_IMR_IFEIE | SPDIFRX_IMR_SYNCDIE | SPDIFRX_IMR_PERRIE;
@@ -327,7 +328,7 @@ static int stm32_spdifrx_start_sync(struct stm32_spdifrx_data *spdifrx)
 	if (ret)
 		return ret;
 
-	spin_lock(&spdifrx->lock);
+	spin_lock_irqsave(&spdifrx->lock, flags);
 
 	spdifrx->refcount++;
 
@@ -362,7 +363,7 @@ static int stm32_spdifrx_start_sync(struct stm32_spdifrx_data *spdifrx)
 				"Failed to start synchronization\n");
 	}
 
-	spin_unlock(&spdifrx->lock);
+	spin_unlock_irqrestore(&spdifrx->lock, flags);
 
 	return ret;
 }
@@ -370,11 +371,12 @@ static int stm32_spdifrx_start_sync(struct stm32_spdifrx_data *spdifrx)
 static void stm32_spdifrx_stop(struct stm32_spdifrx_data *spdifrx)
 {
 	int cr, cr_mask, reg;
+	unsigned long flags;
 
-	spin_lock(&spdifrx->lock);
+	spin_lock_irqsave(&spdifrx->lock, flags);
 
 	if (--spdifrx->refcount) {
-		spin_unlock(&spdifrx->lock);
+		spin_unlock_irqrestore(&spdifrx->lock, flags);
 		return;
 	}
 
@@ -393,7 +395,7 @@ static void stm32_spdifrx_stop(struct stm32_spdifrx_data *spdifrx)
 	regmap_read(spdifrx->regmap, STM32_SPDIFRX_DR, &reg);
 	regmap_read(spdifrx->regmap, STM32_SPDIFRX_CSR, &reg);
 
-	spin_unlock(&spdifrx->lock);
+	spin_unlock_irqrestore(&spdifrx->lock, flags);
 }
 
 static int stm32_spdifrx_dma_ctrl_register(struct device *dev,