irqchip/bcm7120-l2: Perform suspend/resume even without installed child IRQs

Make use of the new irq_chip_generic suspend/resume callbacks.

This is required because if there are no installed child IRQs for this
chip, the irq_chip::irq_{suspend,resume} functions will not be called.
However, we still need to save/restore the forwarding mask, to enable
the top-level GIC interrupt; otherwise, we lose UART output after S3
resume.

In addition to refactoring the callbacks, we have to self-initialize the
mask cache, since the genirq core also doesn't initialize this until the
first child IRQ is installed.

The original problem report is described in extra detail here:
http://lkml.kernel.org/g/20150619224123.GL4917@ld-irv-0074

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: Gregory Fong <gregory.0xf0@gmail.com>
Cc: bcm-kernel-feedback-list@broadcom.com
Cc: linux-mips@linux-mips.org
Cc: Kevin Cernekee <cernekee@chromium.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/1437607300-40858-2-git-send-email-computersforpeace@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/irqchip/irq-bcm7120-l2.c

@@ -80,11 +80,10 @@ static void bcm7120_l2_intc_irq_handle(unsigned int irq, struct irq_desc *desc)
 	chained_irq_exit(chip, desc);
 }
 
-static void bcm7120_l2_intc_suspend(struct irq_data *d)
+static void bcm7120_l2_intc_suspend(struct irq_chip_generic *gc)
 {
-	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
-	struct irq_chip_type *ct = irq_data_get_chip_type(d);
 	struct bcm7120_l2_intc_data *b = gc->private;
+	struct irq_chip_type *ct = gc->chip_types;
 
 	irq_gc_lock(gc);
 	if (b->can_wake)
@@ -93,10 +92,9 @@ static void bcm7120_l2_intc_suspend(struct irq_data *d)
 	irq_gc_unlock(gc);
 }
 
-static void bcm7120_l2_intc_resume(struct irq_data *d)
+static void bcm7120_l2_intc_resume(struct irq_chip_generic *gc)
 {
-	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
-	struct irq_chip_type *ct = irq_data_get_chip_type(d);
+	struct irq_chip_type *ct = gc->chip_types;
 
 	/* Restore the saved mask */
 	irq_gc_lock(gc);
@@ -279,8 +277,15 @@ int __init bcm7120_l2_intc_probe(struct device_node *dn,
 		ct->chip.irq_mask = irq_gc_mask_clr_bit;
 		ct->chip.irq_unmask = irq_gc_mask_set_bit;
 		ct->chip.irq_ack = irq_gc_noop;
-		ct->chip.irq_suspend = bcm7120_l2_intc_suspend;
-		ct->chip.irq_resume = bcm7120_l2_intc_resume;
+		gc->suspend = bcm7120_l2_intc_suspend;
+		gc->resume = bcm7120_l2_intc_resume;
+
+		/*
+		 * Initialize mask-cache, in case we need it for
+		 * saving/restoring fwd mask even w/o any child interrupts
+		 * installed
+		 */
+		gc->mask_cache = irq_reg_readl(gc, ct->regs.mask);
 
 		if (data->can_wake) {
 			/* This IRQ chip can wake the system, set all