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

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Message-ID: <20210402091555.GA2207539@anxtwsw-Precision-3640-Tower>
Date:   Fri, 2 Apr 2021 17:15:55 +0800
From:   Xin Ji <xji@...logixsemi.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Sean Paul <sean@...rly.run>, 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>, 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 Fri, Apr 02, 2021 at 11:59:39AM +0300, Laurent Pinchart wrote:
> Hi Xin,
> 
> On Fri, Apr 02, 2021 at 10:27:08AM +0800, Xin Ji wrote:
> > 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.
> > > >
> > > > 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?
> >
> > 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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fchromium-review.googlesource.com%2Fc%2Fchromiumos%2Fthird_party%2Fkernel%2F%2B%2F2674580&amp;data=04%7C01%7Cxji%40analogixsemi.com%7Cd778885f3d0d4b4358a908d8f5b5c273%7Cb099b0b4f26c4cf59a0fd5be9acab205%7C0%7C0%7C637529508334886979%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=vo8zP8SAhLrQk0%2FWh1OhXHAZzLU9lJ4NLaYddI6t2ZU%3D&amp;reserved=0)
> 
> Please note that upstream review happens on mailing lists, not in
> gerrit. Internal reviews for Chrome OS development are certainly fine
> there, but that will not mean the patch will then be accepted upstream
> as-is, it will still need to go through the upstream review process,
> without any shortcut. I strongly recommend using an upstream-first
> strategy, with public review.
Hi Laurent Pinchart, OK, got it, thanks for the note.

Thanks,
Xin
> 
> > > > > > +
> > > > > >         if (ctx->pdata.is_dpi)
> > > > > >                 ret = anx7625_dpi_config(ctx);
> > > > > >         else
> > > 
> > > /snip
> 
> -- 
> Regards,
> 
> Laurent Pinchart