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Date:   Wed, 5 Sep 2018 16:39:32 +0200
From:   Maxime Ripard <maxime.ripard@bootlin.com>
To:     Icenowy Zheng <icenowy@aosc.io>
Cc:     linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
        Jernej Skrabec <jernej.skrabec@siol.net>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-sunxi@googlegroups.com, Chen-Yu Tsai <wens@csie.org>
Subject: Re: [PATCH 1/3] dt-bindings: change the A64 HDMI PHY binding to R40
Message-ID: <20180905143932.lbytjftmobjtzdsu@flea>
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On Wed, Sep 05, 2018 at 04:05:18PM +0800, Icenowy Zheng wrote:
>=20
>=20
> =E4=BA=8E 2018=E5=B9=B49=E6=9C=885=E6=97=A5 GMT+08:00 =E4=B8=8B=E5=8D=883=
:56:01, Maxime Ripard <maxime.ripard@bootlin.com> =E5=86=99=E5=88=B0:
> >On Wed, Sep 05, 2018 at 03:46:41PM +0800, Icenowy Zheng wrote:
> >>=20
> >>=20
> >> =E4=BA=8E 2018=E5=B9=B49=E6=9C=885=E6=97=A5 GMT+08:00 =E4=B8=8B=E5=8D=
=883:14:35, Maxime Ripard
> ><maxime.ripard@bootlin.com> =E5=86=99=E5=88=B0:
> >> >On Mon, Sep 03, 2018 at 09:34:32PM +0800, Icenowy Zheng wrote:
> >> >> By experiment, the A64 HDMi PHY doesn't support the PLL-VIDEO mux
> >> >> introduced in R40, although it has two PLL-VIDEOs.
> >> >>=20
> >> >> Change the A64 HDMI PHY binding to R40 one.
> >> >>=20
> >> >> This binding is introduced in v4.19, which is still in RC stage,
> >so
> >> >we
> >> >> have change to fix it.
> >> >>=20
> >> >> Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
> >> >
> >> >That doesn't make much sense. The A64 doesn't have any particular
> >> >reason to behave like the R40, and the R40 can definitely use a
> >> >different compatible if it has a different behaviour. But I don't
> >see
> >> >*why* the A64 not behaving like the R40 is a justification to remove
> >> >the A64 compatible. Especially when the R40 was released later.
> >> >
> >> >Add a new compatible, and leave the A64 compatible alone.
> >>=20
> >> But the behavior of A64 compatible will change from double
> >> PLL to single PLL, because the A64 HDMI PHY is proven
> >> to have no double PLL.
> >>=20
> >> Should I then change the A64 compatible behavior and import R40
> >> compatible at the same time?
> >
> >I don't see why you should do both at the same time. Fix the A64, and
> >add the support for the R40, those are two orthogonal changes.
>=20
> Then how to deal with double PLL support? Make them temporarily
> dead during 4.19?

Well, if the PHY doesn't use two PLL, don't use it, ever. Why does it
have to be temporary?

--=20
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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