Re: [PATCH 1/4] dt-bindings: sound: sun4i-spdif: Add Allwinner H6 compatible

From: Maxime Ripard <maxime.ripard@bootlin.com>
To: "Clément Péron" <peron.clem@gmail.com>
Cc: devicetree <devicetree@vger.kernel.org>,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	linux-sunxi <linux-sunxi@googlegroups.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Chen-Yu Tsai <wens@csie.org>, Rob Herring <robh+dt@kernel.org>,
	Jagan Teki <jagan@amarulasolutions.com>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Icenowy Zheng <icenowy@aosc.io>
Subject: Re: [PATCH 1/4] dt-bindings: sound: sun4i-spdif: Add Allwinner H6 compatible
Date: Mon, 15 Apr 2019 10:18:16 +0200	[thread overview]
Message-ID: <20190415081816.2pay4pioc5d4mojf@flea> (raw)
In-Reply-To: <CAJiuCcc0Q8rh8u_30gKi8o07k0+e35UR99ZBHtCjx-DPkJEtdw@mail.gmail.com>

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On Mon, Apr 15, 2019 at 10:09:11AM +0200, Clément Péron wrote:
> Hi,
>
> On Mon, 15 Apr 2019 at 10:04, Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> >
> > Hi,
> >
> > On Thu, Apr 11, 2019 at 11:44:19PM +0200, Clément Péron wrote:
> > > Allwinner H6 has a SPDIF controller with an increase of the fifo
> > > size and the possibility to output the master clock.
> > > However it's still compatible with the already existing driver for
> > > Allwiner H3.
> > >
> > > Add this compatible in the device-tree bindings documentation.
> >
> > How was this tested?
>
> Using Alsa utils on a Beelink GS1 and I check correct output sound on
> my home cinema.
>
> > After looking at the datasheet, it looks like it's still significantly
> > different. In particular:
> >
> >   - The MCLK divider isn't at the same offset
>
> We don't use the MCLK
>
> >   - The bits to flush the FIFO aren't at the same offset
> >   - The FIFO trigger levels aren't at the same offset
> >   - The FIFO status register layout is almost entirely different
>
> We use DMA not FIFO

Well, DMA still uses the FIFOs. And even then, you're kind of missing
the point. The device tree's compatible is about whether a particular
device can be used as another one. How you are using it in the driver
is completely irrelevant.

Maxime

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

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