feat(gicv3): introduce GIC component identification

The GIC specification describes ID registers in each GIC register frame
(PIDRx), which can be used to identify a GIC component. The Arm Ltd. GIC
implementations use certain ID values to identify the distributor, the
redistributors and other parts like ITSes.

Introduce a function that reads those part number IDs, which are spread
over two registers. The actual numbers are only meaningful in connection
with a certain GIC model, which would need to be checked beforehand, by
the caller.

Change-Id: Ia6ff326a1e8b12664e4637bc8e2683d2b5c7721c
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

drivers/arm/gic/v3/gicv3_helpers.c

@@ -393,3 +393,18 @@ unsigned int gicv3_rdistif_get_number_frames(const uintptr_t gicr_frame)
 
 	return count;
 }
+
+unsigned int gicv3_get_component_partnum(const uintptr_t gic_frame)
+{
+	unsigned int part_id;
+
+	/*
+	 * The lower 8 bits of PIDR0, complemented by the lower 4 bits of
+	 * PIDR1 contain a part number identifying the GIC component at a
+	 * particular base address.
+	 */
+	part_id = mmio_read_32(gic_frame + GICD_PIDR0_GICV3) & 0xff;
+	part_id |= (mmio_read_32(gic_frame + GICD_PIDR1_GICV3) << 8) & 0xf00;
+
+	return part_id;
+}

include/drivers/arm/arm_gicv3_common.h

@@ -21,4 +21,8 @@
 #define IIDR_MODEL_ARM_GIC_600AE	U(0x0300043b)
 #define IIDR_MODEL_ARM_GIC_700		U(0x0400043b)
 
+#define PIDR_COMPONENT_ARM_DIST		U(0x492)
+#define PIDR_COMPONENT_ARM_REDIST	U(0x493)
+#define PIDR_COMPONENT_ARM_ITS		U(0x494)
+
 #endif /* ARM_GICV3_COMMON_H */

include/drivers/arm/gicv3.h

@@ -104,6 +104,8 @@
 #define GICD_IROUTER		U(0x6000)
 #define GICD_IROUTERE		U(0x8000)
 
+#define GICD_PIDR0_GICV3	U(0xffe0)
+#define GICD_PIDR1_GICV3	U(0xffe4)
 #define GICD_PIDR2_GICV3	U(0xffe8)
 
 #define IGRPMODR_SHIFT		5
@@ -324,6 +326,8 @@ static inline uintptr_t gicv3_redist_size(uint64_t typer_val)
 #endif
 }
 
+unsigned int gicv3_get_component_partnum(const uintptr_t gic_frame);
+
 static inline bool gicv3_is_intr_id_special_identifier(unsigned int id)
 {
 	return (id >= PENDING_G1S_INTID) && (id <= GIC_SPURIOUS_INTERRUPT);