VC4 GPIO support possibly broken
mzoran at crowfest.net
Sat Mar 18 22:17:42 PDT 2017
Hi Eric and Stefan,
I did some more testing of the driver I submitted to staging, and even
though the mailbox API is functional, I'm finding that the VC4 driver
doesn't appear to be doing the right thing with GPIO handling.
The DT I submitted does make VC4 functional on the RPI 3, but I added
some debugging prints to the driver I submitted and VC4 isn't even
doing any GPIO queries at all.
With the DT I submited, I'm seeing that when VC4 looks up the GPIO
number from the DT it's getting back 0 which doesn't make sense. And
if the GPIO is 0, VC4 is skipping calls to the GPIO.
I also noticed if the GPIO is marked as active-low, VC4 also appears to
be skipping GPIO calls.
Please not that the mailbox API is functional. I did some manual calls
into the mailbox API, and 132 is really working as a HDMI hotplug
detection. I plug in HDMI, I get 1 back. I disconnect HDMI and I get
0 back. So the actual polarity should be GPIO_ACTIVE_HIGH.
More information about the linux-rpi-kernel