Commit 6afb1026 authored Oct 02, 2017 by Daniel Drake Committed by Linus Walleij Oct 19, 2017

pinctrl/amd: fix masking of GPIO interrupts



On Asus laptop models X505BA, X505BP, X542BA and X542BP, the i2c-hid
touchpad (using a GPIO for interrupts) becomes unresponsive after a
few minutes of usage, or after placing two fingers on the touchpad,
which seems to have the effect of queuing up a large amount of input
data to be transferred.

When the touchpad is in unresponsive state, we observed that the GPIO
level-triggered interrupt is still at it's active level, however the
pinctrl-amd driver is not receiving/dispatching more interrupts at this
point.

After the initial interrupt arrives, amd_gpio_irq_mask() is called
however we then see amd_gpio_irq_handler() being called repeatedly for
the same irq; the interrupt mask is not taking effect because of the
following sequence of events:
 - amd_gpio_irq_handler fires, reads and caches pin reg
 - amd_gpio_irq_handler calls generic_handle_irq()
 - During IRQ handling, amd_gpio_irq_mask() is called and modifies pin reg
 - amd_gpio_irq_handler clears interrupt by writing cached value

The stale cached value written at the final stage undoes the masking.
Fix this by re-reading the register before clearing the interrupt.

I also spotted that the interrupt-clearing code can race against
amd_gpio_irq_mask() / amd_gpio_irq_unmask(), so add locking there.
Presumably this race was leading to the loss of interrupts.

After these changes, the touchpad appears to be working fine.

Signed-off-by: Daniel Drake <drake@endlessm.com>
Acked-by: Shah, Nehal-bakulchandra <Nehal-Bakulchandra.shah@amd.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

parent 33d930e5

drivers/pinctrl/pinctrl-amd.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -534,8 +534,16 @@ static irqreturn_t amd_gpio_irq_handler(int irq, void *dev_id)
		continue;
		irq = irq_find_mapping(gc->irqdomain, irqnr + i);
		generic_handle_irq(irq);
		/* Clear interrupt */

		/* Clear interrupt.
		* We must read the pin register again, in case the
		* value was changed while executing
		* generic_handle_irq() above.
		*/
		raw_spin_lock_irqsave(&gpio_dev->lock, flags);
		regval = readl(regs + i);
		writel(regval, regs + i);
		raw_spin_unlock_irqrestore(&gpio_dev->lock, flags);
		ret = IRQ_HANDLED;
		}
		}