diff mbox series

[v2] arm64: dts: allwinner: a64: olinuxino: Fix phy-mode

Message ID 20260822052353.22881-1-roman@riabenko.com (mailing list archive)
State New
Headers
Series [v2] arm64: dts: allwinner: a64: olinuxino: Fix phy-mode |

Commit Message

Roman Riabenko Aug. 22, 2026, 5:23 a.m. UTC 
The 'rgmii' mode does not appear to describe the RGMII timing in Olimex
A64-OlinuXino boards. The PCB layout shows that the clock and data
traces have roughly the same lengths for both RX and TX and, thus, do
not appear to implement the 2 ns RGMII delay or introduce any
significant delay.

According to the KSZ9031RNX datasheet, the PHY adds a typical 1.2 ns RX
delay and no TX delay by default. The 'rgmii-id' mode causes the PHY
driver to enable appropriate internal RGMII delays.

Packet loss in the downlink direction is observed with the 'rgmii' mode
and is severe enough to interfere with downloads and disrupt software
installation. No packet loss is observed with 'rgmii-id'.

Adjusting the TX delay in the DT was found to be unnecessary with
'rgmii-id'.

Signed-off-by: Roman Riabenko <roman@riabenko.com>
---
 arch/arm64/boot/dts/allwinner/sun50i-a64-olinuxino.dts | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Comments

Andrew Lunn Aug. 22, 2026, 2:53 p.m. UTC | #1 
On Sat, Aug 22, 2026 at 08:23:53AM +0300, Roman Riabenko wrote:
> The 'rgmii' mode does not appear to describe the RGMII timing in Olimex
> A64-OlinuXino boards. The PCB layout shows that the clock and data
> traces have roughly the same lengths for both RX and TX and, thus, do
> not appear to implement the 2 ns RGMII delay or introduce any
> significant delay.
> 
> According to the KSZ9031RNX datasheet, the PHY adds a typical 1.2 ns RX
> delay and no TX delay by default. The 'rgmii-id' mode causes the PHY
> driver to enable appropriate internal RGMII delays.
> 
> Packet loss in the downlink direction is observed with the 'rgmii' mode
> and is severe enough to interfere with downloads and disrupt software
> installation. No packet loss is observed with 'rgmii-id'.
> 
> Adjusting the TX delay in the DT was found to be unnecessary with
> 'rgmii-id'.

Nice, thanks for doing a proper analysis.

> Signed-off-by: Roman Riabenko <roman@riabenko.com>

  Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew
diff mbox series

Patch

diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64-olinuxino.dts b/arch/arm64/boot/dts/allwinner/sun50i-a64-olinuxino.dts
index fd3794678c33..8cb2381e21da 100644
--- a/arch/arm64/boot/dts/allwinner/sun50i-a64-olinuxino.dts
+++ b/arch/arm64/boot/dts/allwinner/sun50i-a64-olinuxino.dts
@@ -102,10 +102,9 @@  &ehci1 {
 &emac {
 	pinctrl-names = "default";
 	pinctrl-0 = <&rgmii_pins>;
-	phy-mode = "rgmii";
+	phy-mode = "rgmii-id";
 	phy-handle = <&ext_rgmii_phy>;
 	phy-supply = <&reg_dcdc1>;
-	allwinner,tx-delay-ps = <600>;
 	status = "okay";
 };