irqchip/gic-v3: Add GICv4.1 VPEID size discovery

While GICv4.0 mandates 16 bit worth of VPEIDs, GICv4.1 allows smaller
implementations to be built. Add the required glue to dynamically
compute the limit.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Link: https://lore.kernel.org/r/20191224111055.11836-3-maz@kernel.org

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

@@ -121,7 +121,16 @@ struct its_node {
 #define ITS_ITT_ALIGN		SZ_256
 
 /* The maximum number of VPEID bits supported by VLPI commands */
-#define ITS_MAX_VPEID_BITS	(16)
+#define ITS_MAX_VPEID_BITS						\
+	({								\
+		int nvpeid = 16;					\
+		if (gic_rdists->has_rvpeid &&				\
+		    gic_rdists->gicd_typer2 & GICD_TYPER2_VIL)		\
+			nvpeid = 1 + (gic_rdists->gicd_typer2 &		\
+				      GICD_TYPER2_VID);			\
+									\
+		nvpeid;							\
+	})
 #define ITS_MAX_VPEID		(1 << (ITS_MAX_VPEID_BITS))
 
 /* Convert page order to size in bytes */

drivers/irqchip/irq-gic-v3.c

@@ -1576,6 +1576,9 @@ static int __init gic_init_bases(void __iomem *dist_base,
 
 	pr_info("%d SPIs implemented\n", GIC_LINE_NR - 32);
 	pr_info("%d Extended SPIs implemented\n", GIC_ESPI_NR);
+
+	gic_data.rdists.gicd_typer2 = readl_relaxed(gic_data.dist_base + GICD_TYPER2);
+
 	gic_data.domain = irq_domain_create_tree(handle, &gic_irq_domain_ops,
 						 &gic_data);
 	irq_domain_update_bus_token(gic_data.domain, DOMAIN_BUS_WIRED);

include/linux/irqchip/arm-gic-v3.h

@@ -13,6 +13,7 @@
 #define GICD_CTLR			0x0000
 #define GICD_TYPER			0x0004
 #define GICD_IIDR			0x0008
+#define GICD_TYPER2			0x000C
 #define GICD_STATUSR			0x0010
 #define GICD_SETSPI_NSR			0x0040
 #define GICD_CLRSPI_NSR			0x0048
@@ -89,6 +90,9 @@
 #define GICD_TYPER_ESPIS(typer)						\
 	(((typer) & GICD_TYPER_ESPI) ? GICD_TYPER_SPIS((typer) >> 27) : 0)
 
+#define GICD_TYPER2_VIL			(1U << 7)
+#define GICD_TYPER2_VID			GENMASK(4, 0)
+
 #define GICD_IROUTER_SPI_MODE_ONE	(0U << 31)
 #define GICD_IROUTER_SPI_MODE_ANY	(1U << 31)
 
@@ -615,6 +619,7 @@ struct rdists {
 	void			*prop_table_va;
 	u64			flags;
 	u32			gicd_typer;
+	u32			gicd_typer2;
 	bool			has_vlpis;
 	bool			has_rvpeid;
 	bool			has_direct_lpi;