[PATCH] ARM64: dts: meson-gxbb-odroidc2: switch ethernet phy mode to rgmii-txid

[PATCH] ARM64: dts: meson-gxbb-odroidc2: switch ethernet phy mode to rgmii-txid

[Heiner Kallweit]

Documentation/networking/phy.txt states:
Whenever possible,use the PHY side RGMII delay.

The board uses a RTl8211F phy which supports creating the needed
tx delay internally. Therefore switch to rgmii-txid mode.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts b/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
index 3877dda6..94896139 100644
--- a/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
+++ b/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
@@ -152,6 +152,7 @@
 	pinctrl-0 = <&eth_rgmii_pins>;
 	pinctrl-names = "default";
 	phy-handle = <&eth_phy0>;
+	phy-mode = "rgmii-txid";
 
 	mdio {
 		compatible = "snps,dwmac-mdio";
-- 
2.11.0

[PATCH] ARM64: dts: meson-gxbb-odroidc2: switch ethernet phy mode to rgmii-txid

[Jerome Brunet]

On Fri, 2017-02-10 at 00:09 +0100, Heiner Kallweit wrote:
> Documentation/networking/phy.txt states:
> Whenever possible,use the PHY side RGMII delay.
> 
> The board uses a RTl8211F phy which supports creating the needed
> tx delay internally. Therefore switch to rgmii-txid mode.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
> ?arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts | 1 +
> ?1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
> b/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
> index 3877dda6..94896139 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
> +++ b/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
> @@ -152,6 +152,7 @@
> ?	pinctrl-0 = <&eth_rgmii_pins>;
> ?	pinctrl-names = "default";
> ?	phy-handle = <&eth_phy0>;
> +	phy-mode = "rgmii-txid";
> ?
> ?	mdio {
> ?		compatible = "snps,dwmac-mdio";

Heiner,

In principle, I agree with this patch but:

* We need the patches [0] [1] from net-next to merged first (or pulled
in kevin's tree). Without this, the proposed change would result in a
4ns Tx delay instead of 2ns. If Martin send another version of patch
[2], then "amlogic,tx-delay-ns = <2>;" should be removed for the
odroidc2 as the delay would be introduced by the PHY (the value would
ignored anyway, but it would be misleading)

* We would be changing a configuration tested by many people for a
barely tested one, without any benefits expected. These 2
configurations are supposed to be equivalent, and I'm willing to test
it again once the prerequisites are merged but I'd prefer if more
people could test this and confirm there is no regression before
merging it.

Cheers

Jerome

[0]: commit b765234e72fc ("net: stmmac: dwmac-meson8b: make the RGMII
TX delay configurable")
[1]: commit d6db61a40ee0 ("net: stmmac: don't set tx delay in RGMII_ID
and RGMII_TXID mode")
[2]: https://marc.info/?l=linux-arm-kernel&m=148754182813497&w=2

[PATCH] ARM64: dts: meson-gxbb-odroidc2: switch ethernet phy mode to rgmii-txid

[Heiner Kallweit]

Am 02.03.2017 um 11:22 schrieb Jerome Brunet:
> On Fri, 2017-02-10 at 00:09 +0100, Heiner Kallweit wrote:
>> Documentation/networking/phy.txt states:
>> Whenever possible,use the PHY side RGMII delay.
>>
>> The board uses a RTl8211F phy which supports creating the needed
>> tx delay internally. Therefore switch to rgmii-txid mode.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>> ---
>>  arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
>> b/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
>> index 3877dda6..94896139 100644
>> --- a/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
>> +++ b/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
>> @@ -152,6 +152,7 @@
>>  	pinctrl-0 = <&eth_rgmii_pins>;
>>  	pinctrl-names = "default";
>>  	phy-handle = <&eth_phy0>;
>> +	phy-mode = "rgmii-txid";
>>  
>>  	mdio {
>>  		compatible = "snps,dwmac-mdio";
> 
> Heiner,
> 
> In principle, I agree with this patch but:
> 
> * We need the patches [0] [1] from net-next to merged first (or pulled
> in kevin's tree). Without this, the proposed change would result in a
> 4ns Tx delay instead of 2ns. If Martin send another version of patch
> [2], then "amlogic,tx-delay-ns = <2>;" should be removed for the
> odroidc2 as the delay would be introduced by the PHY (the value would
> ignored anyway, but it would be misleading)
> 
Right ..

> * We would be changing a configuration tested by many people for a
> barely tested one, without any benefits expected. These 2
> configurations are supposed to be equivalent, and I'm willing to test
> it again once the prerequisites are merged but I'd prefer if more
> people could test this and confirm there is no regression before
> merging it.
> 
Also right. There is no urgent need for this patch and I'm totally
fine with waiting for more feedback.
It's just a minor improvement to make the configuration more
in line with the documented best practices.

Heiner

> Cheers
> 
> Jerome
> 
> [0]: commit b765234e72fc ("net: stmmac: dwmac-meson8b: make the RGMII
> TX delay configurable")
> [1]: commit d6db61a40ee0 ("net: stmmac: don't set tx delay in RGMII_ID
> and RGMII_TXID mode")
> [2]: https://marc.info/?l=linux-arm-kernel&m=148754182813497&w=2
> 
> 
>