linux-kernel - [PATCH 5.16 188/200] irqchip/realtek-rtl: Fix off-by-one in routing

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Date:   Mon, 31 Jan 2022 11:57:31 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sander Vanheule <sander@...nheule.net>,
        Marc Zyngier <maz@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.16 188/200] irqchip/realtek-rtl: Fix off-by-one in routing

From: Sander Vanheule <sander@...nheule.net>

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@...nheule.net>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Link: https://lore.kernel.org/r/177b920aa8d8610615692d0e657e509f363c85ca.1641739718.git.sander@svanheule.net
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/irqchip/irq-realtek-rtl.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- 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
 		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
 			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;
 	}