[Intel-gfx] [PATCH 03/11] drm/i915: Disable HDCP signalling on transcoder disable

[Sean Paul]

On Mon, Dec 9, 2019 at 10:18 AM Ville Syrjälä
<ville.syrjala at linux.intel.com> wrote:
>
> On Fri, Dec 06, 2019 at 08:55:09AM -0500, Sean Paul wrote:
> > On Thu, Dec 05, 2019 at 09:33:19PM +0200, Ville Syrjälä wrote:
> > > On Tue, Dec 03, 2019 at 12:36:26PM -0500, Sean Paul wrote:
> > > > From: Sean Paul <seanpaul at chromium.org>
> > > >
> > > > Currently we rely on intel_hdcp_disable() to disable HDCP signalling in
> > > > the DDI Function Control register. This patch adds a safety net by also
> > > > clearing the bit when we disable the transcoder.
> > > >
> > > > Once we have HDCP over MST and disappearing connectors, we want to make
> > > > sure that the signalling is truly disabled even if HDCP teardown doesn't
> > > > go as planned.
> > >
> > > Why wouldn't it go as planned?
> > >
> >
> > Because things can fail in weird and wonderful ways on unplug :-)
>
> Not really.
>

That is a bold position to take, bugs happen, hardware flakes, etc.

> >
> > It's a safety net. I saw this function and figured HDCP signalling should be
> > explicitly cleared here as well.
>
> I call it dead and confusing code.

...adding a bit to an existing register clear is confusing? That might
be a touch hyperbolic.

> If we get here with HDCP still
> enabled we have a more serious bug somewhere else.
>

Ok, I suppose it's your call as to whether you take this patch, feel
free to drop.

Sean

> --
> Ville Syrjälä
> Intel
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