irqchip: mips-gic: Provide VP ID accessor

Provide a gic_read_local_vp_id() function to read the VCNUM field of the
GICs local VP_IDENT register. This will be used by a further patch to
check that the value reported by the GIC matches up with the kernels
calculation.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12334/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

drivers/irqchip/irq-mips-gic.c

@@ -246,6 +246,14 @@ void gic_stop_count(void)
 
 #endif
 
+unsigned gic_read_local_vp_id(void)
+{
+	unsigned long ident;
+
+	ident = gic_read(GIC_REG(VPE_LOCAL, GIC_VP_IDENT));
+	return ident & GIC_VP_IDENT_VCNUM_MSK;
+}
+
 static bool gic_local_irq_is_routable(int intr)
 {
 	u32 vpe_ctl;

include/linux/irqchip/mips-gic.h

@@ -103,6 +103,7 @@
 #define GIC_VPE_SWINT0_MAP_OFS		0x0054
 #define GIC_VPE_SWINT1_MAP_OFS		0x0058
 #define GIC_VPE_OTHER_ADDR_OFS		0x0080
+#define GIC_VP_IDENT_OFS		0x0088
 #define GIC_VPE_WD_CONFIG0_OFS		0x0090
 #define GIC_VPE_WD_COUNT0_OFS		0x0094
 #define GIC_VPE_WD_INITIAL0_OFS		0x0098
@@ -211,6 +212,10 @@
 #define GIC_VPE_SMASK_FDC_SHF		6
 #define GIC_VPE_SMASK_FDC_MSK		(MSK(1) << GIC_VPE_SMASK_FDC_SHF)
 
+/* GIC_VP_IDENT fields */
+#define GIC_VP_IDENT_VCNUM_SHF		0
+#define GIC_VP_IDENT_VCNUM_MSK		(MSK(6) << GIC_VP_IDENT_VCNUM_SHF)
+
 /* GIC nomenclature for Core Interrupt Pins. */
 #define GIC_CPU_INT0		0 /* Core Interrupt 2 */
 #define GIC_CPU_INT1		1 /* .		      */
@@ -278,4 +283,16 @@ static inline int gic_get_usm_range(struct resource *gic_usm_res)
 
 #endif /* CONFIG_MIPS_GIC */
 
+/**
+ * gic_read_local_vp_id() - read the local VPs VCNUM
+ *
+ * Read the VCNUM of the local VP from the GIC_VP_IDENT register and
+ * return it to the caller. This ID should be used to refer to the VP
+ * via the GICs VP-other region, or when calculating an offset to a
+ * bit representing the VP in interrupt masks.
+ *
+ * Return: The VCNUM value for the local VP.
+ */
+extern unsigned gic_read_local_vp_id(void);
+
 #endif /* __LINUX_IRQCHIP_MIPS_GIC_H */