Hey,

Sorry I took this long to look into this.

On Thu, 2017-03-30 at 15:33 +0200, Paul Cercueil wrote:

The Goodix panel triggers an interrupt on touch events. However, its
registers will contain the valid values a short time after the
interrupt, and not when it's raised. At that moment, the 'buffer
status'
bit is set.

Previously, if the 'buffer status' bit was not set when the registers
were read, the data was discarded and no input event was emitted,
causing "finger down" or "finger up" events to be missed sometimes.

This went unnoticed until v4.9, as the DesignWare I2C driver commonly
used with this driver had enough latency for that bug to never
trigger.

Now, in the IRQ handler we will poll (with a timeout)

I don't like the fact that the timeout isn't actually a timeout, but a
loop counter...

 the 'buffer status'
bit and process the data of the panel as soon as this bit gets set.

OK.

Note that the Goodix panel will send a few spurious interrupts after
the
'finger up' event, in which the 'buffer status' bit will never be
set.

Can you please re-send the patch with diff option that makes it easier
to comment on whole patch? There's various block levels being mixed
because they have a linefeed in common...

I'm also CC:ing Hans to test it out as my Goodix tablet is still out of
commission.

Cheers