drm/fsl-dcu: mask all interrupts on initialization

The state of the interrupt mask register on initialization is
unknown, e.g. U-Boot could already used the DCU. So depending on
the boot loader, the outcome of the interrupt mask register could
be different. A defined state is much more preferable. Also, there
is no value in keeping interrupts enabled which we don't need.
Therefor, mask all interrupts on initialization.
Signed-off-by: Stefan Agner <stefan@agner.ch>

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c

@@ -48,7 +48,6 @@ static const struct regmap_config fsl_dcu_regmap_config = {
 static int fsl_dcu_drm_irq_init(struct drm_device *dev)
 {
 	struct fsl_dcu_drm_device *fsl_dev = dev->dev_private;
-	unsigned int value;
 	int ret;
 
 	ret = drm_irq_install(dev, fsl_dev->irq);
@@ -56,9 +55,7 @@ static int fsl_dcu_drm_irq_init(struct drm_device *dev)
 		dev_err(dev->dev, "failed to install IRQ handler\n");
 
 	regmap_write(fsl_dev->regmap, DCU_INT_STATUS, 0);
-	regmap_read(fsl_dev->regmap, DCU_INT_MASK, &value);
-	value &= DCU_INT_MASK_VBLANK;
-	regmap_write(fsl_dev->regmap, DCU_INT_MASK, value);
+	regmap_write(fsl_dev->regmap, DCU_INT_MASK, ~0);
 	regmap_write(fsl_dev->regmap, DCU_UPDATE_MODE,
 		     DCU_UPDATE_MODE_READREG);