linux-kernel - Re: [PATCH v5 21/22] drm/vc4: vec: Add support for more analog TV standards

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Date:   Sun, 16 Oct 2022 21:02:16 +0200
From:   Mateusz Kwiatkowski <kfyatek@...il.com>
To:     Maxime Ripard <maxime@...no.tech>,
        Karol Herbst <kherbst@...hat.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Lyude Paul <lyude@...hat.com>,
        Maxime Ripard <mripard@...nel.org>,
        Emma Anholt <emma@...olt.net>, Chen-Yu Tsai <wens@...e.org>,
        Samuel Holland <samuel@...lland.org>,
        Ben Skeggs <bskeggs@...hat.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>
Cc:     Dom Cobley <dom@...pberrypi.com>, linux-sunxi@...ts.linux.dev,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Noralf Trønnes <noralf@...nnes.org>,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        nouveau@...ts.freedesktop.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-arm-kernel@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org,
        Hans de Goede <hdegoede@...hat.com>,
        Phil Elwell <phil@...pberrypi.com>
Subject: Re: [PATCH v5 21/22] drm/vc4: vec: Add support for more analog TV
 standards

Hi Maxime,

W dniu 13.10.2022 o 15:19, Maxime Ripard pisze:
> From: Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>
>
> Add support for the following composite output modes (all of them are
> somewhat more obscure than the previously defined ones):
>
> - NTSC_443 - NTSC-style signal with the chroma subcarrier shifted to
>   4.43361875 MHz (the PAL subcarrier frequency). Never used for
>   broadcasting, but sometimes used as a hack to play NTSC content in PAL
>   regions (e.g. on VCRs).
> - PAL_N - PAL with alternative chroma subcarrier frequency,
>   3.58205625 MHz. Used as a broadcast standard in Argentina, Paraguay
>   and Uruguay to fit 576i50 with colour in 6 MHz channel raster.
> - PAL60 - 480i60 signal with PAL-style color at normal European PAL
>   frequency. Another non-standard, non-broadcast mode, used in similar
>   contexts as NTSC_443. Some displays support one but not the other.

The current version actually does not support PAL-60. Proper PAL-60 output from
VEC requires configuring it differently than for regular PAL. We have unified
the PAL and PAL-60 modes for the "TV mode" property, but the code here has not
been adjusted appropriately.

I'll try to submit an additional patch that fixes this shortly.

> - SECAM - French frequency-modulated analog color standard; also have
>   been broadcast in Eastern Europe and various parts of Africa and Asia.
>   Uses the same 576i50 timings as PAL.
>
> Also added some comments explaining color subcarrier frequency
> registers.
>
> Acked-by: Noralf Trønnes <noralf@...nnes.org>
> Signed-off-by: Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>
> Signed-off-by: Maxime Ripard <maxime@...no.tech>
> ---
(snip)

Best regards,
Mateusz Kwiatkowski