Merge "TF-A GIC driver: Add barrier before eoi" into integration

drivers/arm/gic/v2/gicv2_main.c

@@ -247,6 +247,15 @@ void gicv2_end_of_interrupt(unsigned int id)
 	assert(driver_data != NULL);
 	assert(driver_data->gicc_base != 0U);
 
+	/*
+	 * Ensure the write to peripheral registers are *complete* before the write
+	 * to GIC_EOIR.
+	 *
+	 * Note: The completion gurantee depends on various factors of system design
+	 * and the barrier is the best core can do by which execution of further
+	 * instructions waits till the barrier is alive.
+	 */
+	dsbishst();
 	gicc_write_EOIR(driver_data->gicc_base, id);
 }
 

include/drivers/arm/gicv3.h

@@ -332,6 +332,18 @@ static inline uint32_t gicv3_get_pending_interrupt_id_sel1(void)
 
 static inline void gicv3_end_of_interrupt_sel1(unsigned int id)
 {
+	/*
+	 * Interrupt request deassertion from peripheral to GIC happens
+	 * by clearing interrupt condition by a write to the peripheral
+	 * register. It is desired that the write transfer is complete
+	 * before the core tries to change GIC state from 'AP/Active' to
+	 * a new state on seeing 'EOI write'.
+	 * Since ICC interface writes are not ordered against Device
+	 * memory writes, a barrier is required to ensure the ordering.
+	 * The dsb will also ensure *completion* of previous writes with
+	 * DEVICE nGnRnE attribute.
+	 */
+	dsbishst();
 	write_icc_eoir1_el1(id);
 }
 
@@ -345,6 +357,18 @@ static inline uint32_t gicv3_acknowledge_interrupt(void)
 
 static inline void gicv3_end_of_interrupt(unsigned int id)
 {
+	/*
+	 * Interrupt request deassertion from peripheral to GIC happens
+	 * by clearing interrupt condition by a write to the peripheral
+	 * register. It is desired that the write transfer is complete
+	 * before the core tries to change GIC state from 'AP/Active' to
+	 * a new state on seeing 'EOI write'.
+	 * Since ICC interface writes are not ordered against Device
+	 * memory writes, a barrier is required to ensure the ordering.
+	 * The dsb will also ensure *completion* of previous writes with
+	 * DEVICE nGnRnE attribute.
+	 */
+	dsbishst();
 	return write_icc_eoir0_el1(id);
 }