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
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.
Both artful and linux-oem can clean cherry pick, and verified this patch
on other machine with the same touchpad issue.
Should have no regression concern by re-reading regval again.
Acked-By: AceLan Kao <[hidden email]>