IRQCHIP: mips-gic: Don't nest calls to do_IRQ()

The GIC chained handlers use do_IRQ() to call the subhandlers.  This
means that irq_enter() calls get nested, which leads to preempt count
looking like we're in nested interrupts, which in turn leads to all
system time being accounted as IRQ time in account_system_time().

Fix it by using generic_handle_irq().  Since these same functions are
used in some systems (if cpu_has_veic) from a low-level vectored
interrupt handler which does not go throught do_IRQ(), we need to do it
conditionally.
Signed-off-by: Rabin Vincent <rabin.vincent@axis.com>
Reviewed-by: Andrew Bresticker <abrestic@chromium.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mips@linux-mips.org
Cc: tglx@linutronix.de
Cc: jason@lakedaemon.net
Patchwork: https://patchwork.linux-mips.org/patch/10545/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

drivers/irqchip/irq-mips-gic.c

@@ -271,7 +271,7 @@ int gic_get_c0_fdc_int(void)
 				  GIC_LOCAL_TO_HWIRQ(GIC_LOCAL_INT_FDC));
 }
 
-static void gic_handle_shared_int(void)
+static void gic_handle_shared_int(bool chained)
 {
 	unsigned int i, intr, virq;
 	unsigned long *pcpu_mask;
@@ -299,6 +299,9 @@ static void gic_handle_shared_int(void)
 	while (intr != gic_shared_intrs) {
 		virq = irq_linear_revmap(gic_irq_domain,
 					 GIC_SHARED_TO_HWIRQ(intr));
+		if (chained)
+			generic_handle_irq(virq);
+		else
 			do_IRQ(virq);
 
 		/* go to next pending bit */
@@ -431,7 +434,7 @@ static struct irq_chip gic_edge_irq_controller = {
 #endif
 };
 
-static void gic_handle_local_int(void)
+static void gic_handle_local_int(bool chained)
 {
 	unsigned long pending, masked;
 	unsigned int intr, virq;
@@ -445,6 +448,9 @@ static void gic_handle_local_int(void)
 	while (intr != GIC_NUM_LOCAL_INTRS) {
 		virq = irq_linear_revmap(gic_irq_domain,
 					 GIC_LOCAL_TO_HWIRQ(intr));
+		if (chained)
+			generic_handle_irq(virq);
+		else
 			do_IRQ(virq);
 
 		/* go to next pending bit */
@@ -509,13 +515,14 @@ static struct irq_chip gic_all_vpes_local_irq_controller = {
 
 static void __gic_irq_dispatch(void)
 {
-	gic_handle_local_int();
-	gic_handle_shared_int();
+	gic_handle_local_int(false);
+	gic_handle_shared_int(false);
 }
 
 static void gic_irq_dispatch(unsigned int irq, struct irq_desc *desc)
 {
-	__gic_irq_dispatch();
+	gic_handle_local_int(true);
+	gic_handle_shared_int(true);
 }
 
 #ifdef CONFIG_MIPS_GIC_IPI