dmaengine: stm32-dma: properly mask irq bits

A single register of the controller holds the information for four dma
channels.
The functions stm32_dma_irq_status() don't mask the relevant bits after
the shift, thus adjacent channel's status is also reported in the returned
value.
Fixed by masking the value before returning it.

Similarly, the function stm32_dma_irq_clear() don't mask the input value
before shifting it, thus an incorrect input value could disable the
interrupts of adjacent channels.
Fixed by masking the input value before using it.

Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/stm32-dma.c

@@ -38,6 +38,10 @@
 #define STM32_DMA_TEI			BIT(3) /* Transfer Error Interrupt */
 #define STM32_DMA_DMEI			BIT(2) /* Direct Mode Error Interrupt */
 #define STM32_DMA_FEI			BIT(0) /* FIFO Error Interrupt */
+#define STM32_DMA_MASKI			(STM32_DMA_TCI \
+					 | STM32_DMA_TEI \
+					 | STM32_DMA_DMEI \
+					 | STM32_DMA_FEI)
 
 /* DMA Stream x Configuration Register */
 #define STM32_DMA_SCR(x)		(0x0010 + 0x18 * (x)) /* x = 0..7 */
@@ -405,7 +409,7 @@ static u32 stm32_dma_irq_status(struct stm32_dma_chan *chan)
 
 	flags = dma_isr >> (((chan->id & 2) << 3) | ((chan->id & 1) * 6));
 
-	return flags;
+	return flags & STM32_DMA_MASKI;
 }
 
 static void stm32_dma_irq_clear(struct stm32_dma_chan *chan, u32 flags)
@@ -420,6 +424,7 @@ static void stm32_dma_irq_clear(struct stm32_dma_chan *chan, u32 flags)
 	 * If (ch % 4) is 2 or 3, left shift the mask by 16 bits.
 	 * If (ch % 4) is 1 or 3, additionally left shift the mask by 6 bits.
 	 */
+	flags &= STM32_DMA_MASKI;
 	dma_ifcr = flags << (((chan->id & 2) << 3) | ((chan->id & 1) * 6));
 
 	if (chan->id & 4)