RE: [PATCH] pinctrl/amd: Use regular interrupt instead of chained

["Shah, Nehal-bakulchandra" <Nehal-bakulchandra.Shah@xxxxxxx>]

Hi Thomas,

Thanks for the patch. However, we have received this issue from multiple people and different disro but it occurs only on Gigabyte hardware. With reference AM4 ryzen board we are not facing this issue.
We are in discussion with gigabyte to check the BIOS part. Once we have clarity on that, we can consider driver part. Also, this code is running on multiple platform of different customers so changing directly at this point of time may be risky in my point of view. Requesting you to hold this patch till we get clarity on bios end.

Thanks for your understanding.

Regards

Nehal

-----Original Message-----
From: linux-gpio-owner@xxxxxxxxxxxxxxx [mailto:linux-gpio-owner@xxxxxxxxxxxxxxx] On Behalf Of Thomas Gleixner
Sent: Wednesday, May 24, 2017 2:54 AM
To: LKML <linux-kernel@xxxxxxxxxxxxxxx>
Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>; linux-gpio@xxxxxxxxxxxxxxx; Borislav Petkov <bp@xxxxxxxxx>; Xue, Ken <Ken.Xue@xxxxxxx>
Subject: [PATCH] pinctrl/amd: Use regular interrupt instead of chained

The AMD pinctrl driver uses a chained interrupt to demultiplex the GPIO interrupts. Kevin Vandeventer reported, that his new AMD Ryzen locks up hard on boot when the AMD pinctrl driver is initialized. The reason is an interrupt storm. It's not clear whether that's caused by hardware or firmware or both.

Using chained interrupts on X86 is a dangerous endavour. If a system is misconfigured or the hardware buggy there is no safety net to catch an interrupt storm.

Convert the driver to use a regular interrupt for the demultiplex handler. This allows the interrupt storm detector to catch the malfunction and lets the system boot up.

This should be backported to stable because it's likely that more users run into this problem as the AMD Ryzen machines are spreading.

Reported-by: Kevin Vandeventer
Link: https://bugzilla.suse.com/show_bug.cgi?id=1034261
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 drivers/pinctrl/pinctrl-amd.c |   91 ++++++++++++++++++------------------------
 1 file changed, 41 insertions(+), 50 deletions(-)

--- a/drivers/pinctrl/pinctrl-amd.c
+++ b/drivers/pinctrl/pinctrl-amd.c
@@ -495,64 +495,54 @@ static struct irq_chip amd_gpio_irqchip
 	.flags        = IRQCHIP_SKIP_SET_WAKE,
 };
 
-static void amd_gpio_irq_handler(struct irq_desc *desc)
+#define PIN_IRQ_PENDING	(BIT(INTERRUPT_STS_OFF) | BIT(WAKE_STS_OFF))
+
+static irqreturn_t amd_gpio_irq_handler(int irq, void *dev_id)
 {
-	u32 i;
-	u32 off;
-	u32 reg;
-	u32 pin_reg;
-	u64 reg64;
-	int handled = 0;
-	unsigned int irq;
+	struct amd_gpio *gpio_dev = dev_id;
+	struct gpio_chip *gc = &gpio_dev->gc;
+	irqreturn_t ret = IRQ_NONE;
+	unsigned int i, irqnr;
 	unsigned long flags;
-	struct irq_chip *chip = irq_desc_get_chip(desc);
-	struct gpio_chip *gc = irq_desc_get_handler_data(desc);
-	struct amd_gpio *gpio_dev = gpiochip_get_data(gc);
+	u32 *regs, regval;
+	u64 status, mask;
 
-	chained_irq_enter(chip, desc);
-	/*enable GPIO interrupt again*/
+	/* Read the wake status */
 	raw_spin_lock_irqsave(&gpio_dev->lock, flags);
-	reg = readl(gpio_dev->base + WAKE_INT_STATUS_REG1);
-	reg64 = reg;
-	reg64 = reg64 << 32;
-
-	reg = readl(gpio_dev->base + WAKE_INT_STATUS_REG0);
-	reg64 |= reg;
+	status = readl(gpio_dev->base + WAKE_INT_STATUS_REG1);
+	status <<= 32;
+	status |= readl(gpio_dev->base + WAKE_INT_STATUS_REG0);
 	raw_spin_unlock_irqrestore(&gpio_dev->lock, flags);
 
-	/*
-	 * first 46 bits indicates interrupt status.
-	 * one bit represents four interrupt sources.
-	*/
-	for (off = 0; off < 46 ; off++) {
-		if (reg64 & BIT(off)) {
-			for (i = 0; i < 4; i++) {
-				pin_reg = readl(gpio_dev->base +
-						(off * 4 + i) * 4);
-				if ((pin_reg & BIT(INTERRUPT_STS_OFF)) ||
-					(pin_reg & BIT(WAKE_STS_OFF))) {
-					irq = irq_find_mapping(gc->irqdomain,
-								off * 4 + i);
-					generic_handle_irq(irq);
-					writel(pin_reg,
-						gpio_dev->base
-						+ (off * 4 + i) * 4);
-					handled++;
-				}
-			}
+	/* Bit 0-45 contain the relevant status bits */
+	status &= (1ULL << 46) - 1;
+	regs = gpio_dev->base;
+	for (mask = 1, irqnr = 0; status; mask <<= 1, regs += 4, irqnr += 4) {
+		if (!(status & mask))
+			continue;
+		status &= ~mask;
+
+		/* Each status bit covers four pins */
+		for (i = 0; i < 4; i++) {
+			regval = readl(regs + i);
+			if (!(regval & PIN_IRQ_PENDING))
+				continue;
+			irq = irq_find_mapping(gc->irqdomain, irqnr + i);
+			generic_handle_irq(irq);
+			/* Clear interrupt */
+			writel(regval, regs + i);
+			ret = IRQ_HANDLED;
 		}
 	}
 
-	if (handled == 0)
-		handle_bad_irq(desc);
-
+	/* Signal EOI to the GPIO unit */
 	raw_spin_lock_irqsave(&gpio_dev->lock, flags);
-	reg = readl(gpio_dev->base + WAKE_INT_MASTER_REG);
-	reg |= EOI_MASK;
-	writel(reg, gpio_dev->base + WAKE_INT_MASTER_REG);
+	regval = readl(gpio_dev->base + WAKE_INT_MASTER_REG);
+	regval |= EOI_MASK;
+	writel(regval, gpio_dev->base + WAKE_INT_MASTER_REG);
 	raw_spin_unlock_irqrestore(&gpio_dev->lock, flags);
 
-	chained_irq_exit(chip, desc);
+	return ret;
 }
 
 static int amd_get_groups_count(struct pinctrl_dev *pctldev) @@ -821,10 +811,11 @@ static int amd_gpio_probe(struct platfor
 		goto out2;
 	}
 
-	gpiochip_set_chained_irqchip(&gpio_dev->gc,
-				 &amd_gpio_irqchip,
-				 irq_base,
-				 amd_gpio_irq_handler);
+	ret = devm_request_irq(&pdev->dev, irq_base, amd_gpio_irq_handler, 0,
+			       KBUILD_MODNAME, gpio_dev);
+	if (ret)
+		goto out2;
+
 	platform_set_drvdata(pdev, gpio_dev);
 
 	dev_dbg(&pdev->dev, "amd gpio driver loaded\n");
--
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