From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Fri, 28 Feb 2020 19:39:41 +0000
Subject: net: dsa: mv88e6xxx: fix lockup on warm boot
Git-commit: 0395823b8d9a4d87bd1bf74359123461c2ae801b
Patch-mainline: 5.6-rc6
References: networking-stable-20_03_14

If the switch is not hardware reset on a warm boot, interrupts can be
left enabled, and possibly pending. This will cause us to enter an
infinite loop trying to service an interrupt we are unable to handle,
thereby preventing the kernel from booting.

Ensure that the global 2 interrupt sources are disabled before we claim
the parent interrupt.

Observed on the ZII development revision B and C platforms with
reworked serdes support, and using reboot -f to reboot the platform.

[js] no mv88e6xxx_reg_lock, mv88e6xxx_g2_int_mask helpers in 4.12 yet.

Fixes: dc30c35be720 ("net: dsa: mv88e6xxx: Implement interrupt support.")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/dsa/mv88e6xxx/global2.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/net/dsa/mv88e6xxx/global2.c
+++ b/drivers/net/dsa/mv88e6xxx/global2.c
@@ -965,6 +965,13 @@ int mv88e6xxx_g2_irq_setup(struct mv88e6
 	if (!chip->dev->of_node)
 		return -EINVAL;
 
+	chip->g2_irq.masked = ~0;
+	mutex_lock(&chip->reg_lock);
+	err = mv88e6xxx_g2_write(chip, GLOBAL2_INT_MASK, ~chip->g2_irq.masked);
+	mutex_unlock(&chip->reg_lock);
+	if (err)
+		return err;
+
 	chip->g2_irq.domain = irq_domain_add_simple(
 		chip->dev->of_node, 16, 0, &mv88e6xxx_g2_irq_domain_ops, chip);
 	if (!chip->g2_irq.domain)
@@ -974,7 +981,6 @@ int mv88e6xxx_g2_irq_setup(struct mv88e6
 		irq_create_mapping(chip->g2_irq.domain, irq);
 
 	chip->g2_irq.chip = mv88e6xxx_g2_irq_chip;
-	chip->g2_irq.masked = ~0;
 
 	chip->device_irq = irq_find_mapping(chip->g1_irq.domain,
 					    GLOBAL_STATUS_IRQ_DEVICE);