Re: [PATCH/RFC] arm64: dts: renesas: ebisu, draak: Limit EtherAVB to 100Mbps

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On Mon, Apr 08, 2019 at 10:41:43AM +0200, Wolfram Sang wrote:
> Hi Simon,
> 
> On Mon, Apr 08, 2019 at 10:31:48AM +0200, Simon Horman wrote:
> > * According to the R-Car Gen3 Hardware Manual Errata for Rev 1.00 of
> >   August 24, 2018, the TX clock internal delay mode isn't supported
> >   on R-Car E3 (r8a77990) and D3 (r8a77995).
> > 
> > * TX clock internal delay mode is required for reliable 1Gbps communication
> >   using the KSZ9031RNX phy present on the Ebisu and Draak boards.
> > 
> > Thus, the E3 based Ebisu and D3 based Draak boards reliably use 1Gbps and
> > the speed should be limited to 100Mbps.
> 
> "cannot" missing?

Yes indeed, thanks for noticing.

> > Based on work by Kazuya Mizuguchi.
> > 
> > Signed-off-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>
> > ---
> >  arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts | 1 +
> >  arch/arm64/boot/dts/renesas/r8a77995-draak.dts | 1 +
> >  2 files changed, 2 insertions(+)
> > 
> >  Based on renesas-devel-20190404-v5.1-rc3
> > 
> > diff --git a/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts b/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts
> > index c72772589953..05214b8dd2c5 100644
> > --- a/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts
> > +++ b/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts
> > @@ -272,6 +272,7 @@
> >  		interrupt-parent = <&gpio2>;
> >  		interrupts = <21 IRQ_TYPE_LEVEL_LOW>;
> >  		reset-gpios = <&gpio1 20 GPIO_ACTIVE_LOW>;
> > +		max-speed = <100>;
> 
> What about adding a comment explaining this speed limit?

Sure, if you think its worth highlighting in the dts as
well as the changelog.





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