irqchip/gic-v3-its: Factor out wait_for_syncr primitive

Waiting for a redistributor to have performed an operation is a
common thing to do, and the idiom is already spread around.
As we're going to make even more use of this, let's have a primitive
that does just that.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Link: https://lore.kernel.org/r/20191027144234.8395-3-maz@kernel.org
Link: https://lore.kernel.org/r/20191108165805.3071-3-maz@kernel.org

drivers/irqchip/irq-gic-v3-its.c

@@ -1093,6 +1093,12 @@ static void lpi_write_config(struct irq_data *d, u8 clr, u8 set)
 		dsb(ishst);
 }
 
+static void wait_for_syncr(void __iomem *rdbase)
+{
+	while (gic_read_lpir(rdbase + GICR_SYNCR) & 1)
+		cpu_relax();
+}
+
 static void lpi_update_config(struct irq_data *d, u8 clr, u8 set)
 {
 	struct its_device *its_dev = irq_data_get_irq_chip_data(d);
@@ -2775,8 +2781,7 @@ static void its_vpe_db_proxy_move(struct its_vpe *vpe, int from, int to)
 
 		rdbase = per_cpu_ptr(gic_rdists->rdist, from)->rd_base;
 		gic_write_lpir(vpe->vpe_db_lpi, rdbase + GICR_CLRLPIR);
-		while (gic_read_lpir(rdbase + GICR_SYNCR) & 1)
-			cpu_relax();
+		wait_for_syncr(rdbase);
 
 		return;
 	}
@@ -2932,8 +2937,7 @@ static void its_vpe_send_inv(struct irq_data *d)
 
 		rdbase = per_cpu_ptr(gic_rdists->rdist, vpe->col_idx)->rd_base;
 		gic_write_lpir(vpe->vpe_db_lpi, rdbase + GICR_INVLPIR);
-		while (gic_read_lpir(rdbase + GICR_SYNCR) & 1)
-			cpu_relax();
+		wait_for_syncr(rdbase);
 	} else {
 		its_vpe_send_cmd(vpe, its_send_inv);
 	}
@@ -2975,8 +2979,7 @@ static int its_vpe_set_irqchip_state(struct irq_data *d,
 			gic_write_lpir(vpe->vpe_db_lpi, rdbase + GICR_SETLPIR);
 		} else {
 			gic_write_lpir(vpe->vpe_db_lpi, rdbase + GICR_CLRLPIR);
-			while (gic_read_lpir(rdbase + GICR_SYNCR) & 1)
-				cpu_relax();
+			wait_for_syncr(rdbase);
 		}
 	} else {
 		if (state)