[PATCH v2] irqchip/mbigen: Fix mbigen node address layout

[Yipeng Zou <zouyipeng@huawei.com>]

The mbigen interrupt chip has its per node registers located in a
contiguous region of page sized chunks. The code maps them into
virtual address space as a contiguous region and determines the
address of a node by using the node ID as index.

                    mbigen chip
       |-----------------|------------|--------------|
   mgn_node_0         mgn_node_1     ...         mgn_node_i
|--------------|   |--------------|       |----------------------|
[0x0000, 0x1000)   [0x1000, 0x2000)       [i*0x1000, (i+1)*0x1000)

This works correctly up to 10 nodes, but then fails because the
11th's array slot is used for the MGN_CLEAR registers.

                         mbigen chip
    |-----------|--------|--------|---------------|--------|
mgn_node_0  mgn_node_1  ...  mgn_clear_register  ...   mgn_node_i
                            |-----------------|
                             [0xA000, 0xB000)

Skip the MGN_CLEAR register space when calculating the
offset for node IDs greater or equal to ten.

Fixes: a6c2f87b8820 ("irqchip/mbigen: Implement the mbigen irq chip operation functions")
Signed-off-by: Yipeng Zou <zouyipeng@huawei.com>
---
 drivers/irqchip/irq-mbigen.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/irqchip/irq-mbigen.c b/drivers/irqchip/irq-mbigen.c
index 093fd42893a7..53cc08387588 100644
--- a/drivers/irqchip/irq-mbigen.c
+++ b/drivers/irqchip/irq-mbigen.c
@@ -64,6 +64,20 @@ struct mbigen_device {
 	void __iomem		*base;
 };
 
+static inline unsigned int get_mbigen_node_offset(unsigned int nid)
+{
+	unsigned int offset = nid * MBIGEN_NODE_OFFSET;
+
+	/*
+	 * To avoid touched clear register in unexpected way, we need to directly
+	 * skip clear register when access to more than 10 mbigen nodes.
+	 */
+	if (nid >= (REG_MBIGEN_CLEAR_OFFSET / MBIGEN_NODE_OFFSET))
+		offset += MBIGEN_NODE_OFFSET;
+
+	return offset;
+}
+
 static inline unsigned int get_mbigen_vec_reg(irq_hw_number_t hwirq)
 {
 	unsigned int nid, pin;
@@ -72,8 +86,7 @@ static inline unsigned int get_mbigen_vec_reg(irq_hw_number_t hwirq)
 	nid = hwirq / IRQS_PER_MBIGEN_NODE + 1;
 	pin = hwirq % IRQS_PER_MBIGEN_NODE;
 
-	return pin * 4 + nid * MBIGEN_NODE_OFFSET
-			+ REG_MBIGEN_VEC_OFFSET;
+	return pin * 4 + get_mbigen_node_offset(nid) + REG_MBIGEN_VEC_OFFSET;
 }
 
 static inline void get_mbigen_type_reg(irq_hw_number_t hwirq,
@@ -88,8 +101,7 @@ static inline void get_mbigen_type_reg(irq_hw_number_t hwirq,
 	*mask = 1 << (irq_ofst % 32);
 	ofst = irq_ofst / 32 * 4;
 
-	*addr = ofst + nid * MBIGEN_NODE_OFFSET
-		+ REG_MBIGEN_TYPE_OFFSET;
+	*addr = ofst + get_mbigen_node_offset(nid) + REG_MBIGEN_TYPE_OFFSET;
 }
 
 static inline void get_mbigen_clear_reg(irq_hw_number_t hwirq,
-- 
2.34.1