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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 26 Sep 2022 12:34:00 +0200
Message-ID: <CAMuHMdXonxXiw4x2PvnQ=xedOQO1y=K0O8g1+ixeSvXmzcOOVw@mail.gmail.com>
Subject: Re: [PATCH v2 10/33] drm/modes: Add a function to generate analog
 display modes
To:     Maxime Ripard <maxime@cerno.tech>
Cc:     Thomas Zimmermann <tzimmermann@suse.de>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Ben Skeggs <bskeggs@redhat.com>,
        David Airlie <airlied@linux.ie>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Emma Anholt <emma@anholt.net>,
        Karol Herbst <kherbst@redhat.com>,
        Samuel Holland <samuel@sholland.org>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Daniel Vetter <daniel@ffwll.ch>, Lyude Paul <lyude@redhat.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Hans de Goede <hdegoede@redhat.com>,
        nouveau@lists.freedesktop.org,
        Dave Stevenson <dave.stevenson@raspberrypi.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Phil Elwell <phil@raspberrypi.com>,
        intel-gfx@lists.freedesktop.org,
        =?UTF-8?Q?Noralf_Tr=C3=B8nnes?= <noralf@tronnes.org>,
        Dom Cobley <dom@raspberrypi.com>, linux-sunxi@lists.linux.dev,
        Mateusz Kwiatkowski <kfyatek+publicgit@gmail.com>,
        dri-devel@lists.freedesktop.org
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Hi Maxime,

On Mon, Sep 26, 2022 at 12:17 PM Maxime Ripard <maxime@cerno.tech> wrote:
> On Fri, Sep 23, 2022 at 11:05:48AM +0200, Thomas Zimmermann wrote:
> > > +   /* 63.556us * 13.5MHz = 858 pixels */
> >
> > I kind of get what the comment wants to tell me, but the units don't add up.
>
> I'm not sure how it doesn't add up?
>
> We have a frequency in Hz (equivalent to s^-1) and a duration in s, so
> the result ends up with no dimension, which is to be expected for a
> number of periods?

To make the units add up, it should be 13.5 Mpixel/s
(which is what a pixel clock of 13.5 MHz really means ;-)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds