irqchip/realtek-rtl: Fix off-by-one in routing

BugLink: https://bugs.launchpad.net/bugs/1959879
commit 91351b5dd0fd494eb2d85e1bb6aca77b067447e0 upstream.

There is an offset between routing values (1..6) and the connected MIPS
CPU interrupts (2..7), but no distinction was made between these two
values.

This issue was previously hidden during testing, because an interrupt
mapping was used where for each required interrupt another (unused)
routing was configured, with an offset of +1.

Offset the CPU IRQ numbers by -1 to retrieve the correct routing value.

Fixes: 9f3a0f34b84a ("irqchip: Add support for Realtek RTL838x/RTL839x interrupt controller")
Signed-off-by: Sander Vanheule <sander@svanheule.net>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/177b920aa8d8610615692d0e657e509f363c85ca.1641739718.git.sander@svanheule.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/drivers/irqchip/irq-realtek-rtl.c b/drivers/irqchip/irq-realtek-rtl.c
index d6788dd93c7bb3b70ae3fa67891612d4d50f5572..568614edd88f4f2b25d6817d4e3ed16d87e90d68 100644 (file)
--- a/drivers/irqchip/irq-realtek-rtl.c
+++ b/drivers/irqchip/irq-realtek-rtl.c
@@ -95,7 +95,8 @@ out:
  * SoC interrupts are cascaded to MIPS CPU interrupts according to the
  * interrupt-map in the device tree. Each SoC interrupt gets 4 bits for
  * the CPU interrupt in an Interrupt Routing Register. Max 32 SoC interrupts
- * thus go into 4 IRRs.
+ * thus go into 4 IRRs. A routing value of '0' means the interrupt is left
+ * disconnected. Routing values {1..15} connect to output lines {0..14}.
  */
 static int __init map_interrupts(struct device_node *node, struct irq_domain *domain)
 {
@@ -134,7 +135,7 @@ static int __init map_interrupts(struct device_node *node, struct irq_domain *do
                of_node_put(cpu_ictl);
 
                cpu_int = be32_to_cpup(imap + 2);
-               if (cpu_int > 7)
+               if (cpu_int > 7 || cpu_int < 2)
                        return -EINVAL;
 
                if (!(mips_irqs_set & BIT(cpu_int))) {
@@ -143,7 +144,8 @@ static int __init map_interrupts(struct device_node *node, struct irq_domain *do
                        mips_irqs_set |= BIT(cpu_int);
                }
 
-               regs[(soc_int * 4) / 32] |= cpu_int << (soc_int * 4) % 32;
+               /* Use routing values (1..6) for CPU interrupts (2..7) */
+               regs[(soc_int * 4) / 32] |= (cpu_int - 1) << (soc_int * 4) % 32;
                imap += 3;
        }