linux-kernel - Re: [PATCH v6 4/5] drm/bridge: anx7625: add HDCP support

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Date:   Fri, 2 Apr 2021 10:27:08 +0800
From:   Xin Ji <xji@...logixsemi.com>
To:     Sean Paul <sean@...rly.run>
Cc:     Foss <robert.foss@...aro.org>,
        Nicolas Boichat <drinkcat@...gle.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        devel@...verdev.osuosl.org,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sheng Pan <span@...logixsemi.com>,
        Jonas Karlman <jonas@...boo.se>,
        David Airlie <airlied@...ux.ie>,
        Bernie Liang <bliang@...logixsemi.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Zhen Li <zhenli@...logixsemi.com>,
        LKML <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Vasily Khoruzhick <anarsoul@...il.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Torsten Duwe <duwe@....de>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH v6 4/5] drm/bridge: anx7625: add HDCP support

On Mon, Mar 29, 2021 at 02:02:08PM -0400, Sean Paul wrote:
> On Mon, Mar 29, 2021 at 6:27 AM Xin Ji <xji@...logixsemi.com> wrote:
> >
> > On Thu, Mar 25, 2021 at 02:19:23PM -0400, Sean Paul wrote:
> > > On Fri, Mar 19, 2021 at 2:35 AM Xin Ji <xji@...logixsemi.com> wrote:
> > > >
> > > > Add HDCP feature, enable HDCP function through chip internal key
> > > > and downstream's capability.
> > > >
> > > > Signed-off-by: Xin Ji <xji@...logixsemi.com>
> > > > ---
> 
> /snip
> 
> > > >  static void anx7625_dp_start(struct anx7625_data *ctx)
> > > >  {
> > > >         int ret;
> > > > @@ -643,6 +787,9 @@ static void anx7625_dp_start(struct anx7625_data *ctx)
> > > >                 return;
> > > >         }
> > > >
> > > > +       /* HDCP config */
> > > > +       anx7625_hdcp_setting(ctx);
> > >
> > > You should really use the "Content Protection" property to
> > > enable/disable HDCP instead of force-enabling it at all times.
> > >
> > > Sean
> > Hi Sean, it's hard to implement "Content Protection" property, we have
> > implemented HDCP in firmware, it is not compatible with it. We don't
> > have interface to get Downstream Cert.
> > Thanks,
> > Xin
> 
> Hi Xin,
> I'm sorry, I don't understand what you mean when you say you don't
> have an interface to get Downstream Cert.
> 
> The Content Protection property is just a means through which
> userspace can turn on and turn off HDCP when it needs. As far as I can
> tell, your patch turns on HDCP when the display is enabled and leaves
> it on until it is disabled. This is undesirable since it forces HDCP
> on the user.
> 
> Is it impossible to enable/disable HDCP outside of display
> enable/disable on your hardware?
> 
> Thanks,
> 
> Sean
Hi Sean, I have commit a test patch on google review site, can you
please help to review it? I'll use Connector's ".atomic_check()"
interface to detect Content Protection property change.
(https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2674580)
Thanks,
Xin
> 
> > >
> > > > +
> > > >         if (ctx->pdata.is_dpi)
> > > >                 ret = anx7625_dpi_config(ctx);
> > > >         else
> 
> /snip