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

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Date:   Mon, 15 Apr 2019 17:06:21 +0200
From:   Ondřej Jirman <megous@...ous.com>
To:     Clément Péron <peron.clem@...il.com>
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        devicetree <devicetree@...r.kernel.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Jagan Teki <jagan@...rulasolutions.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Icenowy Zheng <icenowy@...c.io>
Subject: Re: [PATCH 1/4] dt-bindings: sound: sun4i-spdif: Add Allwinner H6
 compatible

Hi Clement,

On Mon, Apr 15, 2019 at 10:30:38AM +0200, Clément Péron wrote:
> On Mon, 15 Apr 2019 at 10:18, Maxime Ripard <maxime.ripard@...tlin.com> wrote:
> >
> > 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.
> 
> Sorry I meant " We use DMA not PIO".
> 
> I didn't change the driver and the SPDIF is working what's irrelevant
> in declaring the driver as compatible ?
>
> If some feature are missing they can be introduce later as there is a
> special binding for H6 no ?

You have to drop fallback to allwinner,sun8i-h3-spdif at the very least:

+                       #sound-dai-cells = <0>;
+                       compatible = "allwinner,sun50i-h6-spdif",
+                                    "allwinner,sun8i-h3-spdif";
+                       reg = <0x05093000 0x400>;

If the H6 hardware doesn't just implement some optional superset of what H3
does.

regards,
	o.

> Clement
> 
> >
> > Maxime
> >
> > --
> > Maxime Ripard, Bootlin
> > Embedded Linux and Kernel engineering
> > https://bootlin.com
> 
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> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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