linux-kernel - Re: [PATCH v2 7/9] ARM: STi: DT: STiH407: Add FDMA driver dt nodes.

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Message-ID: <20150911164822.GA1150@griffinp-ThinkPad-X1-Carbon-2nd>
Date:	Fri, 11 Sep 2015 17:48:22 +0100
From:	Peter Griffin <peter.griffin@...aro.org>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	srinivas.kandagatla@...il.com, maxime.coquelin@...com,
	patrice.chotard@...com, vinod.koul@...el.com, robh+dt@...nel.org,
	dmaengine@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 7/9] ARM: STi: DT: STiH407: Add FDMA driver dt nodes.

Hi Lee,

On Fri, 11 Sep 2015, Lee Jones wrote:

> On Fri, 11 Sep 2015, Peter Griffin wrote:
> 
> > These nodes are required to get the fdma driver working
> > on STiH407 based silicon.
> > 
> > Signed-off-by: Peter Griffin <peter.griffin@...aro.org>
> > ---
> >  arch/arm/boot/dts/stih407-family.dtsi | 51 +++++++++++++++++++++++++++++++++++
> >  1 file changed, 51 insertions(+)
> > 
> > diff --git a/arch/arm/boot/dts/stih407-family.dtsi b/arch/arm/boot/dts/stih407-family.dtsi
> > index 838b812..da07474b 100644
> > --- a/arch/arm/boot/dts/stih407-family.dtsi
> > +++ b/arch/arm/boot/dts/stih407-family.dtsi
> > @@ -565,5 +565,56 @@
> >  						  <&phy_port2 PHY_TYPE_USB3>;
> >  			};
> >  		};
> > +
> > +		fdma0: fdma0-audio@...0000 {
> 
> I'm not familiar with the FDMA driver, so can't comment knowledgeably,
> but the <dev> part of <dev>@<base_address> should only describe the
> type of hardware.  I believe in this case it should just be
> dma@...20000.  Also notice the leading zero in the address, which I
> believe mitigates possible confusion.  Then you be more specific with
> the label, so something like 'fdma-audio' seems appropriate here.

Ok, can change to that format in v3.

> 
> > +			compatible = "st,stih407-fdma-mpe31";
> > +			reg = <0x8e20000 0x20000>;
> 
> I personally find padding up to 32bits helpful in the addresses.

None of the stih407-family nodes I can see have this padding, including
the ones merged by you.

> 
> > +			interrupts = <GIC_SPI 5 IRQ_TYPE_NONE>;
> > +			dma-channels = <16>;
> > +			#dma-cells = <3>;
> > +			st,fdma-id = <0>;
> 
> We usually shy away from ID properties.  What is it required for in
> this case?

Yes Rob did already mention that over here, see my reply at the bottom
http://www.spinics.net/lists/devicetree/msg92529.html.

However I can't think of any other useful properties we could add
to derive this information. The fdma controller number is used
by the driver to generate a unique firmware filename.

regards,

Peter.
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