pd: ensure tighter timings for IRQ_HPD pulse

In order to ensure we are always meeting the deadlines for the IRQ_HPD
pulse, increase the priority of the processing by moving the rising edge
from the low-priority HOOK task (in a deferred function) to the caller
task (which is the high-priority PD task).
The downside is we are now sleeping in the PD task blocking the
processing of the PD messages during this time.

Changed HPD_DSTREAM_DEBOUNCE_IRQ to 500us instead of 750us. According
to DP spec, the IRQ_HPD pulse width is between 500us and 1000us.

Ensure there is a minimum of 2ms delay in between each IRQ_HPD as specified
by the DP spec, by sleeping before sending the next pulse if needed.
(in practice, this should not wait if we are not too off processing the
messages)

BUG=chromium:711334
BRANCH=glados strago reef oak
TEST=manual, on SKL platform with kernel 3.18 and MST, verify display is
functional on USB-C dock.

Change-Id: Ib2e9dd608c5f1c671cc5a0fd979a5742101375ff
Signed-off-by: Kevin K Wong <kevin.k.wong@intel.com>
Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/508629
Reviewed-by: Todd Broch <tbroch@chromium.org>

0 files changed, 0 insertions, 0 deletions