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Date:   Wed, 12 Apr 2023 09:14:59 +0200
Message-Id: <CRULBWW4VCWG.3KS7HX7P1G4P6@void.crly.cz>
Cc:     "Frank Oltmanns" <frank@oltmanns.dev>,
        "Chen-Yu Tsai" <wens@csie.org>, "David Airlie" <airlied@gmail.com>,
        "Daniel Vetter" <daniel@ffwll.ch>,
        "Jernej Skrabec" <jernej.skrabec@gmail.com>,
        "Samuel Holland" <samuel@sholland.org>,
        <dri-devel@lists.freedesktop.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-sunxi@lists.linux.dev>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] drm/sun4i: uncouple DSI dotclock divider from
 TCON0_DCLK_REG
From:   "Roman Beranek" <romanberanek@icloud.com>
To:     "Maxime Ripard" <maxime@cerno.tech>
References: <20230320161636.24411-1-romanberanek@icloud.com>
 <87wn356ni4.fsf@oltmanns.dev> <20230327202045.ceeqqwjug4ktxtsf@penduick>
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In-Reply-To: <pu3vdz4gnkwgn4thg6tndbnvfroevpnq75bqbfv7yyrh4gkv63@xxl3dsjf2ih3>
Precedence: bulk

On Wed Apr 5, 2023 at 5:03 PM CEST, Maxime Ripard wrote:
> On Wed, Apr 05, 2023 at 02:34:11PM +0200, Roman Beranek wrote:
> > It turns out however that the new dclk rates can't be set exactly as
> > requested without touching pll-video0*, tcon0 now therefore gets
> > reparented from pll-mipi to pll-video0-2x which, as it further turns
> > out, breaks DSI. While simply forbidding the video0-2x mux option seems
> > to me as the right way to go because there's not much use for it with
> > non-DSI interfaces either besides the opportunity to power pll-mipi
> > down, I'd like to run by you first.
>
> Sounds reasonable

Okay, I'm unsure of how to denote that in the code however. Should I
just comment the parent out of the table and put an explanation in
a comment nearby? Or just erase it? I couldn't find an applicable
precedent.

> > * As pll-mipi doesn't have CLK_SET_RATE_PARENT flag set, pll-video0
> >   retains its boot-time rate of 294 MHz set by sunxi-dw-hdmi driver
> >   in u-boot. Why 294 MHz (as opposed to the default rate of 297 MHz)?
> >   The driver actually asks for 297 MHz, clock_set_pll3 rounds it to
> >   294 MHz though because it limits itself to 6 MHz steps.
>
> We could also address that though

Should I include it in v2 of the series, or leave it for later?

Thanks,
Roman