[RFC PATCH v1 21/21] irqchip/sifive-plic: Add GSI conversion support

[Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>]

ACPI uses flat Global System Interrupt Vector space and
hence the GSI number needs to be converted to corresponding
local IRQ number of the interrupt controller. Add a new
gsi_base field in the priv structure to handle this which
will be 0 on DT based systems.

Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
---
 drivers/irqchip/irq-sifive-plic.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index 72d6e06ef52b..1c22070e9cdd 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -68,6 +68,7 @@ struct plic_priv {
 	unsigned long plic_quirks;
 	unsigned int nr_irqs;
 	unsigned long *prio_save;
+	u32 gsi_base;
 };
 
 struct plic_handler {
@@ -314,6 +315,10 @@ static int plic_irq_domain_translate(struct irq_domain *d,
 {
 	struct plic_priv *priv = d->host_data;
 
+	/* For DT, gsi_base is always zero. */
+	if (fwspec->param[0] >= priv->gsi_base)
+		fwspec->param[0] = fwspec->param[0] - priv->gsi_base;
+
 	if (test_bit(PLIC_QUIRK_EDGE_INTERRUPT, &priv->plic_quirks))
 		return irq_domain_translate_twocell(d, fwspec, hwirq, type);
 
@@ -453,6 +458,17 @@ static int plic_probe(struct platform_device *pdev)
 		return -EIO;
 	}
 
+	/*
+	 * Find out GSI base number
+	 *
+	 * Note: DT does not define "riscv,gsi-base" property so GSI
+	 * base is always zero for DT.
+	 */
+	rc = fwnode_property_read_u32_array(dev->fwnode, "riscv,gsi-base",
+					    &priv->gsi_base, 1);
+	if (rc)
+		priv->gsi_base = 0;
+
 	rc = fwnode_property_read_u32_array(dev->fwnode, "riscv,ndev",
 						&nr_irqs, 1);
 	if (rc) {
-- 
2.39.2