linux-kernel - [PATCH] pinctrl: mcp23s08: Get rid of spurious level interrupts

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Message-Id: <20250122120504.1279790-1-mastichi@gmail.com>
Date: Wed, 22 Jan 2025 15:05:04 +0300
From: Dmitry Mastykin <mastichi@...il.com>
To: linus.walleij@...aro.org,
	linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	e.shatokhin@...ro.com,
	arturas.moskvinas@...il.com
Cc: Dmitry Mastykin <mastichi@...il.com>
Subject: [PATCH] pinctrl: mcp23s08: Get rid of spurious level interrupts

irq_mask()/irq_unmask() are not called for nested interrupts. So level
interrupts are never masked, chip's interrupt output is not cleared on
INTCAP or GPIO read, the irq handler is uselessly called again. Nested
irq handler is not called again, because interrupt reason is cleared by
its first call.
/proc/interrupts shows that number of chip's irqs is greater than
number of nested irqs.

This patch adds masking and unmasking level interrupts inside irq handler.

Signed-off-by: Dmitry Mastykin <mastichi@...il.com>
---
 drivers/pinctrl/pinctrl-mcp23s08.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/pinctrl/pinctrl-mcp23s08.c b/drivers/pinctrl/pinctrl-mcp23s08.c
index f384c72d9554..70d7485ada36 100644
--- a/drivers/pinctrl/pinctrl-mcp23s08.c
+++ b/drivers/pinctrl/pinctrl-mcp23s08.c
@@ -382,6 +382,7 @@ static irqreturn_t mcp23s08_irq(int irq, void *data)
 {
 	struct mcp23s08 *mcp = data;
 	int intcap, intcon, intf, i, gpio, gpio_orig, intcap_mask, defval, gpinten;
+	bool need_unmask = false;
 	unsigned long int enabled_interrupts;
 	unsigned int child_irq;
 	bool intf_set, intcap_changed, gpio_bit_changed,
@@ -396,9 +397,6 @@ static irqreturn_t mcp23s08_irq(int irq, void *data)
 		goto unlock;
 	}
 
-	if (mcp_read(mcp, MCP_INTCAP, &intcap))
-		goto unlock;
-
 	if (mcp_read(mcp, MCP_INTCON, &intcon))
 		goto unlock;
 
@@ -408,6 +406,16 @@ static irqreturn_t mcp23s08_irq(int irq, void *data)
 	if (mcp_read(mcp, MCP_DEFVAL, &defval))
 		goto unlock;
 
+	/* Mask level interrupts to avoid their immediate reactivation after clearing */
+	if (intcon) {
+		need_unmask = true;
+		if (mcp_write(mcp, MCP_GPINTEN, gpinten & ~intcon))
+			goto unlock;
+	}
+
+	if (mcp_read(mcp, MCP_INTCAP, &intcap))
+		goto unlock;
+
 	/* This clears the interrupt(configurable on S18) */
 	if (mcp_read(mcp, MCP_GPIO, &gpio))
 		goto unlock;
@@ -470,9 +478,18 @@ static irqreturn_t mcp23s08_irq(int irq, void *data)
 		}
 	}
 
+	if (need_unmask) {
+		mutex_lock(&mcp->lock);
+		goto unlock;
+	}
+
 	return IRQ_HANDLED;
 
 unlock:
+	if (need_unmask)
+		if (mcp_write(mcp, MCP_GPINTEN, gpinten))
+			dev_err(mcp->chip.parent, "can't unmask GPINTEN\n");
+
 	mutex_unlock(&mcp->lock);
 	return IRQ_HANDLED;
 }
-- 
2.34.1