MIPS: smp-cps: Ensure our VP ident calculation is correct

When bringing up a CPU, ensure that its local ID as provided by the GIC
matches up with our calculation of it. This is vital, since if the
condition doesn't hold then we won't have configured interrupts
correctly for the VP.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: Niklas Cassel <niklas.cassel@axis.com>
Cc: Ezequiel Garcia <ezequiel.garcia@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12335/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/smp-cps.c

@@ -307,6 +307,17 @@ static void cps_init_secondary(void)
 	if (cpu_has_mipsmt)
 		dmt();
 
+	if (mips_cm_revision() >= CM_REV_CM3) {
+		unsigned ident = gic_read_local_vp_id();
+
+		/*
+		 * Ensure that our calculation of the VP ID matches up with
+		 * what the GIC reports, otherwise we'll have configured
+		 * interrupts incorrectly.
+		 */
+		BUG_ON(ident != mips_cm_vp_id(smp_processor_id()));
+	}
+
 	change_c0_status(ST0_IM, STATUSF_IP2 | STATUSF_IP3 | STATUSF_IP4 |
 				 STATUSF_IP5 | STATUSF_IP6 | STATUSF_IP7);
 }