pinctrl: bcm2835: Workaround for edge IRQ loss

It has been observed that edge events can be lost when GPIO edges occur
close to each other. Investigation suggests this is due to a hardware
bug, although no mechanism has been identified.

Work around the event loss by moving the IRQ acknowledgement into the
main ISR, adding missing events by explicit level-change detection.

See: https://forums.raspberrypi.com/viewtopic.php?t=350295

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

diff --git a/drivers/pinctrl/bcm/pinctrl-bcm2835.c b/drivers/pinctrl/bcm/pinctrl-bcm2835.c
index dfc651b..ac26569 100644 (file)
--- a/drivers/pinctrl/bcm/pinctrl-bcm2835.c
+++ b/drivers/pinctrl/bcm/pinctrl-bcm2835.c
@@ -420,15 +420,32 @@ static void bcm2835_gpio_irq_handle_bank(struct bcm2835_pinctrl *pc,
        unsigned long events;
        unsigned offset;
        unsigned gpio;
+       u32 levs, levs2;
 
        events = bcm2835_gpio_rd(pc, GPEDS0 + bank * 4);
+       levs = bcm2835_gpio_rd(pc, GPLEV0 + bank * 4);
        events &= mask;
        events &= pc->enabled_irq_map[bank];
+       bcm2835_gpio_wr(pc, GPEDS0 + bank * 4, events);
+
+retry:
        for_each_set_bit(offset, &events, 32) {
                gpio = (32 * bank) + offset;
                generic_handle_domain_irq(pc->gpio_chip.irq.domain,
                                          gpio);
        }
+       events = bcm2835_gpio_rd(pc, GPEDS0 + bank * 4);
+       levs2 = bcm2835_gpio_rd(pc, GPLEV0 + bank * 4);
+
+       events |= levs2 & ~levs & bcm2835_gpio_rd(pc, GPREN0 + bank * 4);
+       events |= ~levs2 & levs & bcm2835_gpio_rd(pc, GPFEN0 + bank * 4);
+       events &= mask;
+       events &= pc->enabled_irq_map[bank];
+       if (events) {
+               bcm2835_gpio_wr(pc, GPEDS0 + bank * 4, events);
+               levs = levs2;
+               goto retry;
+       }
 }
 
 static void bcm2835_gpio_irq_handler(struct irq_desc *desc)
@@ -668,11 +685,7 @@ static int bcm2835_gpio_irq_set_type(struct irq_data *data, unsigned int type)
 
 static void bcm2835_gpio_irq_ack(struct irq_data *data)
 {
-       struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
-       struct bcm2835_pinctrl *pc = gpiochip_get_data(chip);
-       unsigned gpio = irqd_to_hwirq(data);
-
-       bcm2835_gpio_set_bit(pc, GPEDS0, gpio);
+       /* Nothing to do - the main interrupt handler includes the ACK */
 }
 
 static int bcm2835_gpio_irq_set_wake(struct irq_data *data, unsigned int on)