linux-kernel - Re: [PATCH v1 24/35] drm/vc4: vec: Add support for more analog TV standards

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Message-ID: <20220815083702.ipcmdwzkh2fxvdp7@houat>
Date:   Mon, 15 Aug 2022 10:37:02 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Mateusz Kwiatkowski <kfyatek@...il.com>
Cc:     Jernej Skrabec <jernej.skrabec@...il.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Jerome Brunet <jbrunet@...libre.com>,
        Samuel Holland <samuel@...lland.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel@...ll.ch>, Emma Anholt <emma@...olt.net>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Noralf Trønnes <noralf@...nnes.org>,
        Kevin Hilman <khilman@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Phil Elwell <phil@...pberrypi.com>,
        linux-arm-kernel@...ts.infradead.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        linux-amlogic@...ts.infradead.org, dri-devel@...ts.freedesktop.org,
        Dom Cobley <dom@...pberrypi.com>
Subject: Re: [PATCH v1 24/35] drm/vc4: vec: Add support for more analog TV
 standards

Hi,

On Fri, Jul 29, 2022 at 07:55:30PM +0200, Mateusz Kwiatkowski wrote:
> Hi Maxime,
> 
> I think that declaring PAL-B and SECAM-B as the only supported 576i
> norms is a bit random.

Starting with this patch, PAL-N should be supported as well, right?

> Norms B, D, G, H, I, K, K1 and L (for both PAL and SECAM) are
> essentially identical if we're talking about baseband signals, AFAIK
> they only differ when those are modulated as RF signals. I'm not sure
> if there's a point to differentiating those (that's more about patch
> 05/35) unless we need to deal with some device that actually features
> an RF modulator.

What I was aiming for is to have all the cases we have in all the
drivers covered so that we can make that property generic. i915
declares and uses all those variants:

https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/i915/display/intel_sdvo.c#L68

Especially since it's i915 and it's pretty much the standard as far as
the uAPI goes, I'd rather avoid any regression there.

> But if we do want to have all those norms separate, then I'd say that
> VC4 should declare support for all of those, and all should map to the
> same VEC settings. Some users from e.g. the UK might think that they
> won't get proper picture if PAL-I is not on the list of supported
> norms. Same goes for e.g. SECAM-D/K in the former Soviet territories,
> and so on.

I'd be open to it, but we can always extend vc4 to support those modes
later on. The work you did to make that easier should make it trivial.

Maxime

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