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

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Message-ID: <20190415081816.2pay4pioc5d4mojf@flea>
Date:   Mon, 15 Apr 2019 10:18:16 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Clément Péron <peron.clem@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Icenowy Zheng <icenowy@...c.io>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        devicetree <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH 1/4] dt-bindings: sound: sun4i-spdif: Add Allwinner H6
 compatible

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@...tlin.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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