irqchip/mips-gic: Use the correct local interrupt map registers

The MIPS GIC contains a block of registers used to map local interrupts
to a particular CPU interrupt pin. Since these registers are found at a
consecutive range of addresses we access them using an index, via the
(read|write)_gic_v[lo]_map accessor functions. We currently use values
from enum mips_gic_local_interrupt as those indices.

Unfortunately whilst enum mips_gic_local_interrupt provides the correct
offsets for bits in the pending & mask registers, the ordering of the
map registers is subtly different... Compared with the ordering of
pending & mask bits, the map registers move the FDC from the end of the
list to index 3 after the timer interrupt. As a result the performance
counter & software interrupts are therefore at indices 4-6 rather than
indices 3-5.

Notably this causes problems with performance counter interrupts being
incorrectly mapped on some systems, and presumably will also cause
problems for FDC interrupts.

Introduce a function to map from enum mips_gic_local_interrupt to the
index of the corresponding map register, and use it to ensure we access
the map registers for the correct interrupts.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Fixes: a0dc5cb5e3 ("irqchip: mips-gic: Simplify gic_local_irq_domain_map()")
Fixes: da61fcf9d6 ("irqchip: mips-gic: Use irq_cpu_online to (un)mask all-VP(E) IRQs")
Reported-and-tested-by: Archer Yan <ayan@wavecomp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: stable@vger.kernel.org # v4.14+
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/mips/include/asm/mips-gic.h

@@ -314,6 +314,36 @@ static inline bool mips_gic_present(void)
 	return IS_ENABLED(CONFIG_MIPS_GIC) && mips_gic_base;
 }
 
+/**
+ * mips_gic_vx_map_reg() - Return GIC_Vx_<intr>_MAP register offset
+ * @intr: A GIC local interrupt
+ *
+ * Determine the index of the GIC_VL_<intr>_MAP or GIC_VO_<intr>_MAP register
+ * within the block of GIC map registers. This is almost the same as the order
+ * of interrupts in the pending & mask registers, as used by enum
+ * mips_gic_local_interrupt, but moves the FDC interrupt & thus offsets the
+ * interrupts after it...
+ *
+ * Return: The map register index corresponding to @intr.
+ *
+ * The return value is suitable for use with the (read|write)_gic_v[lo]_map
+ * accessor functions.
+ */
+static inline unsigned int
+mips_gic_vx_map_reg(enum mips_gic_local_interrupt intr)
+{
+	/* WD, Compare & Timer are 1:1 */
+	if (intr <= GIC_LOCAL_INT_TIMER)
+		return intr;
+
+	/* FDC moves to after Timer... */
+	if (intr == GIC_LOCAL_INT_FDC)
+		return GIC_LOCAL_INT_TIMER + 1;
+
+	/* As a result everything else is offset by 1 */
+	return intr + 1;
+}
+
 /**
  * gic_get_c0_compare_int() - Return cp0 count/compare interrupt virq
  *

drivers/irqchip/irq-mips-gic.c

@@ -388,7 +388,7 @@ static void gic_all_vpes_irq_cpu_online(struct irq_data *d)
 	intr = GIC_HWIRQ_TO_LOCAL(d->hwirq);
 	cd = irq_data_get_irq_chip_data(d);
 
-	write_gic_vl_map(intr, cd->map);
+	write_gic_vl_map(mips_gic_vx_map_reg(intr), cd->map);
 	if (cd->mask)
 		write_gic_vl_smask(BIT(intr));
 }
@@ -517,7 +517,7 @@ static int gic_irq_domain_map(struct irq_domain *d, unsigned int virq,
 	spin_lock_irqsave(&gic_lock, flags);
 	for_each_online_cpu(cpu) {
 		write_gic_vl_other(mips_cm_vp_id(cpu));
-		write_gic_vo_map(intr, map);
+		write_gic_vo_map(mips_gic_vx_map_reg(intr), map);
 	}
 	spin_unlock_irqrestore(&gic_lock, flags);