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Date:   Thu, 18 Aug 2022 17:34:42 +0200
From:   Maxime Ripard <maxime@cerno.tech>
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Jernej Skrabec <jernej.skrabec@gmail.com>,
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Subject: Re: [PATCH v1 05/35] drm/connector: Add TV standard property
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On Thu, Aug 18, 2022 at 05:20:42PM +0200, Geert Uytterhoeven wrote:
> Hi Maxime,
>=20
> On Thu, Aug 18, 2022 at 4:54 PM Maxime Ripard <maxime@cerno.tech> wrote:
> > On Wed, Aug 17, 2022 at 04:04:24PM +0200, Geert Uytterhoeven wrote:
> > > On Wed, Aug 17, 2022 at 3:19 PM Maxime Ripard <maxime@cerno.tech> wro=
te:
> > > > 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>=
 wrote:
> > > > > > On Wed, Aug 17, 2022 at 10:35:07AM +0200, Geert Uytterhoeven wr=
ote:
> > > > > > > On Wed, Aug 17, 2022 at 9:47 AM Maxime Ripard <maxime@cerno.t=
ech> wrote:
> > > > > > > > On Wed, Aug 17, 2022 at 09:31:18AM +0200, Geert Uytterhoeve=
n wrote:
> > > > > > > > > On Tue, Aug 16, 2022 at 5:50 PM Maxime Ripard <maxime@cer=
no.tech> wrote:
> > > > > > > > > > On Tue, Aug 16, 2022 at 04:43:44PM +0200, Geert Uytterh=
oeven wrote:
> > > > > > > > > > > > > > > Either you have to add them here (e.g. "hd720=
p50" and "hd720p60"), or
> > > > > > > > > > > > > > > handle them through "@<refresh>".  The latter=
 would impact "[PATCH v1
> > > > > > > > > > > > > > > 09/35] drm/modes: Move named modes parsing to=
 a separate function", as
> > > > > > > > > > > > > > > currently a named mode and a refresh rate can=
't be specified both.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > I think the former would make more sense. It si=
mplifies a bit the
> > > > > > > > > > > > > > parser, and we're going to use a named mode any=
way.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > As "[PATCH v1 34/35] drm/modes: Introduce the=
 tv_mode property as a
> > > > > > > > > > > > > > > command-line option" uses a separate "tv_mode=
" option, 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 =
named mode hd720p50,
> > > > > > > > > > > > > > which would be equivalent to 1280x720,tv_mode=
=3Dhd720p
> > > > > > > > > > > > >
> > > > > > > > > > > > > So where's the field rate in "1280x720,tv_mode=3D=
hd720p"?
> > > > > > > > > > > >
> > > > > > > > > > > > Yeah, sorry I meant 1280x720@50,tv_mode=3Dhd720p
> > > > > > > > > > >
> > > > > > > > > > > Above you said "I think the former would make more se=
nse", so that
> > > > > > > > > > > should be "1280x720,tv_mode=3Dhd720p50"?
> > > > > > > > > >
> > > > > > > > > > No, 720p at 50Hz would be either hd720p50 or 1280x720@5=
0,tv_mode=3Dhd720p
> > > > > > > > > > and 60Hz would be hd720p60 or 1280x720@60,tv_mode=3Dhd7=
20p
> > > > > > > > >
> > > > > > > > > I disagree: hd720p50 and hd720p60 are different TV modes.
> > > > > > > >
> > > > > > > > I agree, and I don't see how that command-line doesn't expr=
ess that?
> > > > > > >
> > > > > > > Oh, I see what you mean: yes, it expresses that.
> > > > > > > But it is inconsistent with the NTSC/PAL/SECAM/hd{480,576}[ip=
] modes,
> > > > > > > where the TV mode specifies both number of lines and frame ra=
te.
> > > > > >
> > > > > > 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 w=
ith
> > > > > 625 lines and 25 frames/s, "640x480,tv_mode=3DPAL-M" would give m=
e a
> > > > > mode with 525 lines and 30 frames/s.
> > > >
> > > > In that series, "640x480,tv_mode=3DPAL-N" would be rejected as inva=
lid:
> > > >
> > > > https://lore.kernel.org/dri-devel/20220728-rpi-analog-tv-properties=
-v1-14-3d53ae722097@cerno.tech/
> > >
> > > 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?
>=20
> My concern is that you want to call the TV mode "hd720p", which
> does not dictate the frame rate.
> I would like to have both "720p50" and "720p60", as they do dictate
> the frame rate, like all the non-hd modes.

But they don't?

The refresh rate is part of the drm_display_mode, whereas that property
is metadata and entirely separate from the display mode.

You can even change it without changing the mode at all

Maxime

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