[Intel-gfx] [PATCH] drm/i915: storm detection documentation update

[Daniel Vetter]

On Wed, Jul 08, 2015 at 06:54:06PM +0530, Sivakumar Thulasimani wrote:
> 
> 
> On 7/7/2015 5:01 PM, Daniel Vetter wrote:
> >On Tue, Jul 07, 2015 at 04:10:49PM +0530, Sivakumar Thulasimani wrote:
> >>From: "Thulasimani,Sivakumar" <sivakumar.thulasimani at intel.com>
> >>
> >>Update the hotplug documentation to explain that hotplug storm
> >>is not expected for Display port panels and hence is not handled
> >>in current code.
> >>
> >>Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani at intel.com>
> >>---
> >>  drivers/gpu/drm/i915/intel_hotplug.c |    4 ++++
> >>  1 file changed, 4 insertions(+)
> >>
> >>diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
> >>index bac91a1..7dc5e6a 100644
> >>--- a/drivers/gpu/drm/i915/intel_hotplug.c
> >>+++ b/drivers/gpu/drm/i915/intel_hotplug.c
> >>@@ -66,6 +66,10 @@
> >>   * while before being re-enabled. The intention is to mitigate issues raising
> >>   * from broken hardware triggering massive amounts of interrupts and grinding
> >>   * the system to a halt.
> >>+ *
> >>+ * Hotplug interrupt storm is not expected on Display port panel, hence the
> >>+ * current code only handles disabling and later enabling of HPD interrupts
> >>+ * for HDMI panels through the storm handling set of functions.
> >This isn't accurate, we handle storms on everything _but_ DP (tv, vga,
> >sdvo, ...). I'd go with
> >
> >  * Hotplug interrupt storm is not expected on Display port panel, hence the
> >  * current code doesn't handle irq reenabling when a DP sink is connected
> >  * and the hpd is handled by the DP callbacks. But on DP+ ports
> >  * storms are still handled correctly in all other cases (e.g. due to HDMI
> >  * sinks).
> >
> >Could still be improved I think.
> >
> >-Daniel
> >
> Sorry i don't get the "DP+" reference here. By DP+, do you mean dongles ?
> passive dongles will report them selves as HDMI to respective detect
> routines
> active dongles will be still treated as DP hence not handling HPD will apply
> to any
> display connected through active dongle as well.

DP+ is DP with support for HDMI with level shifter cables (i.e. all the
ports on intel chips). I just wanted to make it clear that storm handling
doesn't work if we have a confirmed DP sink on the port, but will work in
any other cases (nothing or HDMI sink or DVI or whatever connected). Like
I said some room for improvement ;-)
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch