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Date:   Thu, 18 Aug 2022 16:54:36 +0200
From:   Maxime Ripard <maxime@cerno.tech>
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Jernej Skrabec <jernej.skrabec@gmail.com>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
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        Neil Armstrong <narmstrong@baylibre.com>,
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Subject: Re: [PATCH v1 05/35] drm/connector: Add TV standard property
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On Wed, Aug 17, 2022 at 04:04:24PM +0200, Geert Uytterhoeven wrote:
> Hi Maxime,
>=20
> On Wed, Aug 17, 2022 at 3:19 PM Maxime Ripard <maxime@cerno.tech> wrote:
> > On Wed, Aug 17, 2022 at 03:05:52PM +0200, Geert Uytterhoeven wrote:
> > > On Wed, Aug 17, 2022 at 1:15 PM Maxime Ripard <maxime@cerno.tech> wro=
te:
> > > > On Wed, Aug 17, 2022 at 10:35:07AM +0200, Geert Uytterhoeven wrote:
> > > > > On Wed, Aug 17, 2022 at 9:47 AM Maxime Ripard <maxime@cerno.tech>=
 wrote:
> > > > > > On Wed, Aug 17, 2022 at 09:31:18AM +0200, Geert Uytterhoeven wr=
ote:
> > > > > > > On Tue, Aug 16, 2022 at 5:50 PM Maxime Ripard <maxime@cerno.t=
ech> wrote:
> > > > > > > > On Tue, Aug 16, 2022 at 04:43:44PM +0200, Geert Uytterhoeve=
n wrote:
> > > > > > > > > > > > > Either you have to add them here (e.g. "hd720p50"=
 and "hd720p60"), or
> > > > > > > > > > > > > handle them through "@<refresh>".  The latter wou=
ld impact "[PATCH v1
> > > > > > > > > > > > > 09/35] drm/modes: Move named modes parsing to a s=
eparate function", as
> > > > > > > > > > > > > currently a named mode and a refresh rate can't b=
e specified both.
> > > > > > > > > > > >
> > > > > > > > > > > > I think the former would make more sense. It simpli=
fies a bit the
> > > > > > > > > > > > parser, and we're going to use a named mode anyway.
> > > > > > > > > > > >
> > > > > > > > > > > > > As "[PATCH v1 34/35] drm/modes: Introduce the tv_=
mode property as a
> > > > > > > > > > > > > command-line option" uses a separate "tv_mode" op=
tion, and not the main
> > > > > > > > > > > > > mode name, I think you want to add them here.
> > > > > > > > > > > >
> > > > > > > > > > > > It's a separate story I think, we could have a name=
d mode hd720p50,
> > > > > > > > > > > > which would be equivalent to 1280x720,tv_mode=3Dhd7=
20p
> > > > > > > > > > >
> > > > > > > > > > > So where's the field rate in "1280x720,tv_mode=3Dhd72=
0p"?
> > > > > > > > > >
> > > > > > > > > > Yeah, sorry I meant 1280x720@50,tv_mode=3Dhd720p
> > > > > > > > >
> > > > > > > > > Above you said "I think the former would make more sense"=
, so that
> > > > > > > > > should be "1280x720,tv_mode=3Dhd720p50"?
> > > > > > > >
> > > > > > > > No, 720p at 50Hz would be either hd720p50 or 1280x720@50,tv=
_mode=3Dhd720p
> > > > > > > > and 60Hz would be hd720p60 or 1280x720@60,tv_mode=3Dhd720p
> > > > > > >
> > > > > > > I disagree: hd720p50 and hd720p60 are different TV modes.
> > > > > >
> > > > > > I agree, and I don't see how that command-line doesn't express =
that?
> > > > >
> > > > > Oh, I see what you mean: yes, it expresses that.
> > > > > But it is inconsistent with the NTSC/PAL/SECAM/hd{480,576}[ip] mo=
des,
> > > > > where the TV mode specifies both number of lines and frame rate.
> > > >
> > > > Only if we're using a named mode, and naming is hard :)
> > >
> > > That's not true: "640x480,tv_mode=3DPAL-N" would give me a mode with
> > > 625 lines and 25 frames/s, "640x480,tv_mode=3DPAL-M" would give me a
> > > mode with 525 lines and 30 frames/s.
> >
> > In that series, "640x480,tv_mode=3DPAL-N" would be rejected as invalid:
> >
> > https://lore.kernel.org/dri-devel/20220728-rpi-analog-tv-properties-v1-=
14-3d53ae722097@cerno.tech/
>=20
> It would become supported once the ideas from thread "[PATCH v1 04/35]
> drm/modes: Introduce 480i and 576i modes" are implemented...

Indeed, but I'm still not sure what your concern is here.
"640x480,tv_mode=3DPAL-N" and "640x480,tv_mode=3DPAL-M" are both fairly
obvious.

You were initially saying that you had concern over the inconsistency of
NTSC/PAL/SECAM where the TV mode would specify a number of lines and
frame rate, but hd720p50 also specifies a number of line and frame rate?

Maxime

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