drm/omap: remove read_irqenable()

We only use read_irqenable() to flush posted write. Instead of having a
separate function for this, do the flush implicitly in write_irqenable().
Thus we can remove read_irqenable().

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

drivers/gpu/drm/omapdrm/dss/dispc.c

@@ -3782,11 +3782,6 @@ static void dispc_clear_irqstatus(u32 mask)
 	dispc_write_reg(DISPC_IRQSTATUS, mask);
 }
 
-static u32 dispc_read_irqenable(void)
-{
-	return dispc_read_reg(DISPC_IRQENABLE);
-}
-
 static void dispc_write_irqenable(u32 mask)
 {
 	u32 old_mask = dispc_read_reg(DISPC_IRQENABLE);
@@ -3795,6 +3790,9 @@ static void dispc_write_irqenable(u32 mask)
 	dispc_clear_irqstatus((mask ^ old_mask) & mask);
 
 	dispc_write_reg(DISPC_IRQENABLE, mask);
+
+	/* flush posted write */
+	dispc_read_reg(DISPC_IRQENABLE);
 }
 
 void dispc_enable_sidle(void)
@@ -4345,7 +4343,6 @@ static void dispc_errata_i734_wa(void)
 static const struct dispc_ops dispc_ops = {
 	.read_irqstatus = dispc_read_irqstatus,
 	.clear_irqstatus = dispc_clear_irqstatus,
-	.read_irqenable = dispc_read_irqenable,
 	.write_irqenable = dispc_write_irqenable,
 
 	.request_irq = dispc_request_irq,

drivers/gpu/drm/omapdrm/dss/omapdss.h

@@ -880,7 +880,6 @@ void dss_mgr_unregister_framedone_handler(enum omap_channel channel,
 struct dispc_ops {
 	u32 (*read_irqstatus)(void);
 	void (*clear_irqstatus)(u32 mask);
-	u32 (*read_irqenable)(void);
 	void (*write_irqenable)(u32 mask);
 
 	int (*request_irq)(irq_handler_t handler, void *dev_id);

drivers/gpu/drm/omapdrm/omap_irq.c

@@ -41,7 +41,6 @@ static void omap_irq_update(struct drm_device *dev)
 	DBG("irqmask=%08x", irqmask);
 
 	priv->dispc_ops->write_irqenable(irqmask);
-	priv->dispc_ops->read_irqenable();        /* flush posted write */
 }
 
 static void omap_irq_wait_handler(struct omap_irq_wait *wait)