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From:   Vladimir Oltean <vladimir.oltean@nxp.com>
To:     linux-arm-kernel@lists.infradead.org
Cc:     Andrew Lunn <andrew@lunn.ch>,
        Gregory Clement <gregory.clement@bootlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org,
        =?UTF-8?q?Marek=20Beh=C3=BAn?= <kabel@kernel.org>,
        =?UTF-8?q?Pali=20Roh=C3=A1r?= <pali@kernel.org>
Subject: [PATCH 1/2] pinctrl: armada-37xx: make irq_lock a raw spinlock to avoid invalid wait context
Date:   Sun, 17 Jul 2022 02:37:44 +0300
Message-Id: <20220716233745.1704677-2-vladimir.oltean@nxp.com>
In-Reply-To: <20220716233745.1704677-1-vladimir.oltean@nxp.com>
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The irqchip->irq_set_type method is called by __irq_set_trigger() under
the desc->lock raw spinlock.

The armada-37xx implementation, armada_37xx_irq_set_type(), takes a
plain spinlock, the kind that becomes sleepable on RT.

Therefore, this is an invalid locking scheme for which we get a kernel
splat stating just that ("[ BUG: Invalid wait context ]"), because the
context in which the plain spinlock may sleep is atomic due to the raw
spinlock. We need to go raw spinlocks all the way.

Replace the driver's irq_lock with a raw spinlock, to disable preemption
even on RT.

Fixes: 2f227605394b ("pinctrl: armada-37xx: Add irqchip support")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 drivers/pinctrl/mvebu/pinctrl-armada-37xx.c | 38 ++++++++++-----------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/drivers/pinctrl/mvebu/pinctrl-armada-37xx.c b/drivers/pinctrl/mvebu/pinctrl-armada-37xx.c
index a140b6bfbfaa..8fddc67271b4 100644
--- a/drivers/pinctrl/mvebu/pinctrl-armada-37xx.c
+++ b/drivers/pinctrl/mvebu/pinctrl-armada-37xx.c
@@ -102,7 +102,7 @@ struct armada_37xx_pinctrl {
 	struct device			*dev;
 	struct gpio_chip		gpio_chip;
 	struct irq_chip			irq_chip;
-	spinlock_t			irq_lock;
+	raw_spinlock_t			irq_lock;
 	struct pinctrl_desc		pctl;
 	struct pinctrl_dev		*pctl_dev;
 	struct armada_37xx_pin_group	*groups;
@@ -523,9 +523,9 @@ static void armada_37xx_irq_ack(struct irq_data *d)
 	unsigned long flags;
 
 	armada_37xx_irq_update_reg(&reg, d);
-	spin_lock_irqsave(&info->irq_lock, flags);
+	raw_spin_lock_irqsave(&info->irq_lock, flags);
 	writel(d->mask, info->base + reg);
-	spin_unlock_irqrestore(&info->irq_lock, flags);
+	raw_spin_unlock_irqrestore(&info->irq_lock, flags);
 }
 
 static void armada_37xx_irq_mask(struct irq_data *d)
@@ -536,10 +536,10 @@ static void armada_37xx_irq_mask(struct irq_data *d)
 	unsigned long flags;
 
 	armada_37xx_irq_update_reg(&reg, d);
-	spin_lock_irqsave(&info->irq_lock, flags);
+	raw_spin_lock_irqsave(&info->irq_lock, flags);
 	val = readl(info->base + reg);
 	writel(val & ~d->mask, info->base + reg);
-	spin_unlock_irqrestore(&info->irq_lock, flags);
+	raw_spin_unlock_irqrestore(&info->irq_lock, flags);
 }
 
 static void armada_37xx_irq_unmask(struct irq_data *d)
@@ -550,10 +550,10 @@ static void armada_37xx_irq_unmask(struct irq_data *d)
 	unsigned long flags;
 
 	armada_37xx_irq_update_reg(&reg, d);
-	spin_lock_irqsave(&info->irq_lock, flags);
+	raw_spin_lock_irqsave(&info->irq_lock, flags);
 	val = readl(info->base + reg);
 	writel(val | d->mask, info->base + reg);
-	spin_unlock_irqrestore(&info->irq_lock, flags);
+	raw_spin_unlock_irqrestore(&info->irq_lock, flags);
 }
 
 static int armada_37xx_irq_set_wake(struct irq_data *d, unsigned int on)
@@ -564,14 +564,14 @@ static int armada_37xx_irq_set_wake(struct irq_data *d, unsigned int on)
 	unsigned long flags;
 
 	armada_37xx_irq_update_reg(&reg, d);
-	spin_lock_irqsave(&info->irq_lock, flags);
+	raw_spin_lock_irqsave(&info->irq_lock, flags);
 	val = readl(info->base + reg);
 	if (on)
 		val |= (BIT(d->hwirq % GPIO_PER_REG));
 	else
 		val &= ~(BIT(d->hwirq % GPIO_PER_REG));
 	writel(val, info->base + reg);
-	spin_unlock_irqrestore(&info->irq_lock, flags);
+	raw_spin_unlock_irqrestore(&info->irq_lock, flags);
 
 	return 0;
 }
@@ -583,7 +583,7 @@ static int armada_37xx_irq_set_type(struct irq_data *d, unsigned int type)
 	u32 val, reg = IRQ_POL;
 	unsigned long flags;
 
-	spin_lock_irqsave(&info->irq_lock, flags);
+	raw_spin_lock_irqsave(&info->irq_lock, flags);
 	armada_37xx_irq_update_reg(&reg, d);
 	val = readl(info->base + reg);
 	switch (type) {
@@ -607,11 +607,11 @@ static int armada_37xx_irq_set_type(struct irq_data *d, unsigned int type)
 		break;
 	}
 	default:
-		spin_unlock_irqrestore(&info->irq_lock, flags);
+		raw_spin_unlock_irqrestore(&info->irq_lock, flags);
 		return -EINVAL;
 	}
 	writel(val, info->base + reg);
-	spin_unlock_irqrestore(&info->irq_lock, flags);
+	raw_spin_unlock_irqrestore(&info->irq_lock, flags);
 
 	return 0;
 }
@@ -626,7 +626,7 @@ static int armada_37xx_edge_both_irq_swap_pol(struct armada_37xx_pinctrl *info,
 
 	regmap_read(info->regmap, INPUT_VAL + 4*reg_idx, &l);
 
-	spin_lock_irqsave(&info->irq_lock, flags);
+	raw_spin_lock_irqsave(&info->irq_lock, flags);
 	p = readl(info->base + IRQ_POL + 4 * reg_idx);
 	if ((p ^ l) & (1 << bit_num)) {
 		/*
@@ -647,7 +647,7 @@ static int armada_37xx_edge_both_irq_swap_pol(struct armada_37xx_pinctrl *info,
 		ret = -1;
 	}
 
-	spin_unlock_irqrestore(&info->irq_lock, flags);
+	raw_spin_unlock_irqrestore(&info->irq_lock, flags);
 	return ret;
 }
 
@@ -664,11 +664,11 @@ static void armada_37xx_irq_handler(struct irq_desc *desc)
 		u32 status;
 		unsigned long flags;
 
-		spin_lock_irqsave(&info->irq_lock, flags);
+		raw_spin_lock_irqsave(&info->irq_lock, flags);
 		status = readl_relaxed(info->base + IRQ_STATUS + 4 * i);
 		/* Manage only the interrupt that was enabled */
 		status &= readl_relaxed(info->base + IRQ_EN + 4 * i);
-		spin_unlock_irqrestore(&info->irq_lock, flags);
+		raw_spin_unlock_irqrestore(&info->irq_lock, flags);
 		while (status) {
 			u32 hwirq = ffs(status) - 1;
 			u32 virq = irq_find_mapping(d, hwirq +
@@ -695,12 +695,12 @@ static void armada_37xx_irq_handler(struct irq_desc *desc)
 
 update_status:
 			/* Update status in case a new IRQ appears */
-			spin_lock_irqsave(&info->irq_lock, flags);
+			raw_spin_lock_irqsave(&info->irq_lock, flags);
 			status = readl_relaxed(info->base +
 					       IRQ_STATUS + 4 * i);
 			/* Manage only the interrupt that was enabled */
 			status &= readl_relaxed(info->base + IRQ_EN + 4 * i);
-			spin_unlock_irqrestore(&info->irq_lock, flags);
+			raw_spin_unlock_irqrestore(&info->irq_lock, flags);
 		}
 	}
 	chained_irq_exit(chip, desc);
@@ -731,7 +731,7 @@ static int armada_37xx_irqchip_register(struct platform_device *pdev,
 	struct device *dev = &pdev->dev;
 	unsigned int i, nr_irq_parent;
 
-	spin_lock_init(&info->irq_lock);
+	raw_spin_lock_init(&info->irq_lock);
 
 	nr_irq_parent = of_irq_count(np);
 	if (!nr_irq_parent) {
-- 
2.34.1