On Tue, Jan 17, 2017 at 9:19 PM, Julia Cartwright [off-list ref] wrote:

Can you give the following patch a try?  Even though this problem is
only observable on -rt kernels, the below patch is suitable for
inclusion in mainline.  (The below is ontop of -next, you may have to
finnagle it a bit to work on the linaro frankenkernel).

This looks like one of the RT cases pointed out by Grygorii i
Documentation/gpio/driver.txt
and the patch looks fine.

Once you have confirmation that it solves the problem, add
a Tested-by: tag and send to the GPIO mailinglist & me and
make sure to get Björn Andersson on the CC so he can review
it swiftly.

Yours,
Linus Walleij