[PATCH v7 2/4] gpio: mxc: fix both_edges bit operations

["Peng Fan (OSS)" <peng.fan@oss.nxp.com>]

From: Peng Fan <peng.fan@nxp.com>

gpio_set_irq_type() can be called concurrently for different pins on
the same port.  The IRQ core serializes per irq descriptor, but
different pins have different descriptors, so on SMP systems two
concurrent gpio_set_irq_type() calls for pins on the same port run
without mutual exclusion.

The read-modify-write of port->both_edges is performed outside the
port-wide scoped_guard(gpio_generic_lock_irqsave) section, so
concurrent updates for different pins can overwrite each other,
causing missed interrupts or stuck IRQ lines on dual-edge triggered
pins.

The original uniprocessor MXC SoCs were not affected; the race
became reachable on multi-core i.MX7 and i.MX8 SoCs that reuse this
driver.

Convert both_edges from u32 to unsigned long and use set_bit(),
clear_bit(), and test_bit() to make the modifications atomic.

Fixes: 910862ec092c ("mxc: emulate GPIO interrupt on both-edges")
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
 drivers/gpio/gpio-mxc.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpio-mxc.c b/drivers/gpio/gpio-mxc.c
index e05f276a50e8..7e17d7668980 100644
--- a/drivers/gpio/gpio-mxc.c
+++ b/drivers/gpio/gpio-mxc.c
@@ -7,6 +7,7 @@
 // Authors: Daniel Mack, Juergen Beisert.
 // Copyright (C) 2004-2010 Freescale Semiconductor, Inc. All Rights Reserved.
 
+#include <linux/bitops.h>
 #include <linux/cleanup.h>
 #include <linux/clk.h>
 #include <linux/err.h>
@@ -68,7 +69,7 @@ struct mxc_gpio_port {
 	struct irq_domain *domain;
 	struct gpio_generic_chip gen_gc;
 	struct device *dev;
-	u32 both_edges;
+	unsigned long both_edges;
 	struct mxc_gpio_reg_saved gpio_saved_reg;
 	bool power_off;
 	u32 wakeup_pads;
@@ -168,7 +169,7 @@ static int gpio_set_irq_type(struct irq_data *d, u32 type)
 	int edge;
 	void __iomem *reg = port->base;
 
-	port->both_edges &= ~(1 << gpio_idx);
+	clear_bit(gpio_idx, &port->both_edges);
 	switch (type) {
 	case IRQ_TYPE_EDGE_RISING:
 		edge = GPIO_INT_RISE_EDGE;
@@ -188,7 +189,7 @@ static int gpio_set_irq_type(struct irq_data *d, u32 type)
 				edge = GPIO_INT_HIGH_LEV;
 				pr_debug("mxc: set GPIO %d to high trigger\n", gpio_idx);
 			}
-			port->both_edges |= 1 << gpio_idx;
+			set_bit(gpio_idx, &port->both_edges);
 		}
 		break;
 	case IRQ_TYPE_LEVEL_LOW:
@@ -259,7 +260,7 @@ static void mxc_gpio_irq_handler(struct mxc_gpio_port *port, u32 irq_stat)
 	while (irq_stat != 0) {
 		int irqoffset = fls(irq_stat) - 1;
 
-		if (port->both_edges & (1 << irqoffset))
+		if (test_bit(irqoffset, &port->both_edges))
 			mxc_flip_edge(port, irqoffset);
 
 		generic_handle_domain_irq(port->domain, irqoffset);

-- 
2.51.0