1 files changed, 103 insertions, 0 deletions
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index d24bebdfb064..4154a1613dba 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -586,3 +586,106 @@ static struct irq_chip its_irq_chip = {
 	.irq_eoi		= its_eoi_irq,
 	.irq_set_affinity	= its_set_affinity,
 };
+
+/*
+ * How we allocate LPIs:
+ *
+ * The GIC has id_bits bits for interrupt identifiers. From there, we
+ * must subtract 8192 which are reserved for SGIs/PPIs/SPIs. Then, as
+ * we allocate LPIs by chunks of 32, we can shift the whole thing by 5
+ * bits to the right.
+ *
+ * This gives us (((1UL << id_bits) - 8192) >> 5) possible allocations.
+ */
+#define IRQS_PER_CHUNK_SHIFT	5
+#define IRQS_PER_CHUNK		(1 << IRQS_PER_CHUNK_SHIFT)
+
+static unsigned long *lpi_bitmap;
+static u32 lpi_chunks;
+static DEFINE_SPINLOCK(lpi_lock);
+
+static int its_lpi_to_chunk(int lpi)
+{
+	return (lpi - 8192) >> IRQS_PER_CHUNK_SHIFT;
+}
+
+static int its_chunk_to_lpi(int chunk)
+{
+	return (chunk << IRQS_PER_CHUNK_SHIFT) + 8192;
+}
+
+static int its_lpi_init(u32 id_bits)
+{
+	lpi_chunks = its_lpi_to_chunk(1UL << id_bits);
+
+	lpi_bitmap = kzalloc(BITS_TO_LONGS(lpi_chunks) * sizeof(long),
+			     GFP_KERNEL);
+	if (!lpi_bitmap) {
+		lpi_chunks = 0;
+		return -ENOMEM;
+	}
+
+	pr_info("ITS: Allocated %d chunks for LPIs\n", (int)lpi_chunks);
+	return 0;
+}
+
+static unsigned long *its_lpi_alloc_chunks(int nr_irqs, int *base, int *nr_ids)
+{
+	unsigned long *bitmap = NULL;
+	int chunk_id;
+	int nr_chunks;
+	int i;
+
+	nr_chunks = DIV_ROUND_UP(nr_irqs, IRQS_PER_CHUNK);
+
+	spin_lock(&lpi_lock);
+
+	do {
+		chunk_id = bitmap_find_next_zero_area(lpi_bitmap, lpi_chunks,
+						      0, nr_chunks, 0);
+		if (chunk_id < lpi_chunks)
+			break;
+
+		nr_chunks--;
+	} while (nr_chunks > 0);
+
+	if (!nr_chunks)
+		goto out;
+
+	bitmap = kzalloc(BITS_TO_LONGS(nr_chunks * IRQS_PER_CHUNK) * sizeof (long),
+			 GFP_ATOMIC);
+	if (!bitmap)
+		goto out;
+
+	for (i = 0; i < nr_chunks; i++)
+		set_bit(chunk_id + i, lpi_bitmap);
+
+	*base = its_chunk_to_lpi(chunk_id);
+	*nr_ids = nr_chunks * IRQS_PER_CHUNK;
+
+out:
+	spin_unlock(&lpi_lock);
+
+	return bitmap;
+}
+
+static void its_lpi_free(unsigned long *bitmap, int base, int nr_ids)
+{
+	int lpi;
+
+	spin_lock(&lpi_lock);
+
+	for (lpi = base; lpi < (base + nr_ids); lpi += IRQS_PER_CHUNK) {
+		int chunk = its_lpi_to_chunk(lpi);
+		BUG_ON(chunk > lpi_chunks);
+		if (test_bit(chunk, lpi_bitmap)) {
+			clear_bit(chunk, lpi_bitmap);
+		} else {
+			pr_err("Bad LPI chunk %d\n", chunk);
+		}
+	}
+
+	spin_unlock(&lpi_lock);
+
+	kfree(bitmap);
+}