Hi Simon, On 17/07/2019 13:57, 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. I believe you might mean 'can not' reliable use 1Gbps here :-) Regards Kieran > > Based on work by Kazuya Mizuguchi. > > Signed-off-by: Simon Horman <horms+renesas@xxxxxxxxxxxx> > > --- > > This is a repost of this change. > > In earlier review Andrew Lunn suggested that we may be able to take a > different approach to this problem by using delays provided by the > KSZ9031RNX PHY. In particular MMD address 2h, Register 8h - > RGMII Clock Pad Skew. > > I have consulted with Renesas regarding this suggestion, however, > unfortunately it appears that the delays provided by this solution > would be insufficient to allow for reliable 1Gbps communication. > > At this point I believe the safest option is to apply this patch. > --- > arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts | 1 + > arch/arm64/boot/dts/renesas/r8a77995-draak.dts | 1 + > 2 files changed, 2 insertions(+) > > diff --git a/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts b/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts > index 83fc13ac3fa1..3d3d6d438a05 100644 > --- a/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts > +++ b/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts > @@ -271,6 +271,7 @@ > interrupt-parent = <&gpio2>; > interrupts = <21 IRQ_TYPE_LEVEL_LOW>; > reset-gpios = <&gpio1 20 GPIO_ACTIVE_LOW>; > + max-speed = <100>; > }; > }; > > diff --git a/arch/arm64/boot/dts/renesas/r8a77995-draak.dts b/arch/arm64/boot/dts/renesas/r8a77995-draak.dts > index 0711170b26b1..eb153323ed13 100644 > --- a/arch/arm64/boot/dts/renesas/r8a77995-draak.dts > +++ b/arch/arm64/boot/dts/renesas/r8a77995-draak.dts > @@ -175,6 +175,7 @@ > reg = <0>; > interrupt-parent = <&gpio5>; > interrupts = <19 IRQ_TYPE_LEVEL_LOW>; > + max-speed = <100>; > }; > }; > >
