GIC-600: Fix power up sequence

Arm's GIC-600 features a Power Register (GICR_PWRR),
which needs to be programmed to enable redistributor
operation. Section 3.6.1 in the GIC-600 TRM describes
the power-up and power-down sequence in pseudo code,
which deviates from the current TF-A implementation
in drivers/arm/gic/v3/gic600.c.
For powering on a redistributor, the pseudo code suggests
to loop over the whole sequence (check for transition,
write request bit) instead of just looping over the
ready bit read as TF-A does in gic600_pwr_on().
This patch fixes GIC-600 power up sequence according
to the TRM.

Change-Id: I445c480e96ba356b69a2d8e5308ffe6c0a97f45b
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>

drivers/arm/gic/v3/gic600.c

 /*
- * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
 /*
- * Driver for GIC600-specific features. This driver only overrides APIs that are
- * different to those generic ones in GICv3 driver.
+ * Driver for GIC-600 specific features. This driver only overrides
+ * APIs that are different to those generic ones in GICv3 driver.
  *
- * GIC600 supports independently power-gating redistributor interface.
+ * GIC-600 supports independently power-gating redistributor interface.
  */
 
 #include <assert.h>
@@ -18,22 +18,28 @@
 
 #include "gicv3_private.h"
 
-/* GIC600-specific register offsets */
+/* GIC-600 specific register offsets */
 #define GICR_PWRR	0x24
 
 /* GICR_PWRR fields */
 #define PWRR_RDPD_SHIFT		0
+#define PWRR_RDAG_SHIFT		1
 #define PWRR_RDGPD_SHIFT	2
 #define PWRR_RDGPO_SHIFT	3
 
+#define PWRR_RDPD	(1 << PWRR_RDPD_SHIFT)
+#define PWRR_RDAG	(1 << PWRR_RDAG_SHIFT)
 #define PWRR_RDGPD	(1 << PWRR_RDGPD_SHIFT)
 #define PWRR_RDGPO	(1 << PWRR_RDGPO_SHIFT)
 
-/* Values to write to GICR_PWRR register to power redistributor */
+/*
+ * Values to write to GICR_PWRR register to power redistributor
+ * for operating through the core (GICR_PWRR.RDAG = 0)
+ */
 #define PWRR_ON		(0 << PWRR_RDPD_SHIFT)
 #define PWRR_OFF	(1 << PWRR_RDPD_SHIFT)
 
-/* GIC600-specific accessor functions */
+/* GIC-600 specific accessor functions */
 static void gicr_write_pwrr(uintptr_t base, unsigned int val)
 {
 	mmio_write_32(base + GICR_PWRR, val);
@@ -44,39 +50,46 @@ static uint32_t gicr_read_pwrr(uintptr_t base)
 	return mmio_read_32(base + GICR_PWRR);
 }
 
-static int gicr_group_powering_down(uint32_t pwrr)
+static void gicr_wait_group_not_in_transit(uintptr_t base)
 {
-	/*
-	 * Whether the redistributor group power down operation is in transit:
-	 * i.e. it's intending to, but not finished yet.
-	 */
-	return ((pwrr & PWRR_RDGPD) && !(pwrr & PWRR_RDGPO));
+	/* Check group not transitioning: RDGPD == RDGPO */
+	while (((gicr_read_pwrr(base) & PWRR_RDGPD) >> PWRR_RDGPD_SHIFT) !=
+		((gicr_read_pwrr(base) & PWRR_RDGPO) >> PWRR_RDGPO_SHIFT))
+		;
 }
 
 static void gic600_pwr_on(uintptr_t base)
 {
-	/* Power on redistributor */
-	gicr_write_pwrr(base, PWRR_ON);
+	do {	/* Wait until group not transitioning */
+		gicr_wait_group_not_in_transit(base);
 
-	/* Wait until the power on state is reflected */
-	while (gicr_read_pwrr(base) & PWRR_RDGPO)
-		;
+		/* Power on redistributor */
+		gicr_write_pwrr(base, PWRR_ON);
+
+		/*
+		 * Wait until the power on state is reflected.
+		 * If RDPD == 0 then powered on.
+		 */
+	} while ((gicr_read_pwrr(base) & PWRR_RDPD) != PWRR_ON);
 }
 
 static void gic600_pwr_off(uintptr_t base)
 {
+	/* Wait until group not transitioning */
+	gicr_wait_group_not_in_transit(base);
+
 	/* Power off redistributor */
 	gicr_write_pwrr(base, PWRR_OFF);
 
 	/*
 	 * If this is the last man, turning this redistributor frame off will
-	 * result in the group itself being powered off. In that case, wait as
-	 * long as it's in transition, or has aborted the transition altogether
-	 * for any reason.
+	 * result in the group itself being powered off and RDGPD = 1.
+	 * In that case, wait as long as it's in transition, or has aborted
+	 * the transition altogether for any reason.
 	 */
-	if (gicr_read_pwrr(base) & PWRR_RDGPD) {
-		while (gicr_group_powering_down(gicr_read_pwrr(base)))
-			;
+	if ((gicr_read_pwrr(base) & PWRR_RDGPD) != 0) {
+		/* Wait until group not transitioning */
+		gicr_wait_group_not_in_transit(base);
 	}
 }
 
@@ -91,7 +104,7 @@ void gicv3_distif_post_restore(unsigned int proc_num)
 }
 
 /*
- * Power off GIC600 redistributor
+ * Power off GIC-600 redistributor
  */
 void gicv3_rdistif_off(unsigned int proc_num)
 {
@@ -109,7 +122,7 @@ void gicv3_rdistif_off(unsigned int proc_num)
 }
 
 /*
- * Power on GIC600 redistributor
+ * Power on GIC-600 redistributor
  */
 void gicv3_rdistif_on(unsigned int proc_num)
 {