The StarFive VisionFive V1 SBC uses a Motorcomm YT8521 PHY supporting
RGMII-ID, but requires manual adjustment of the RX internal delay to
work properly.

The default RX delay provided by the driver is 1.95 ns, which proves to
be too high. Applying a 50% reduction seems to mitigate the issue.

Also note this adjustment is not necessary on BeagleV Starlight SBC,
which uses a Microchip PHY.  Hence, there is no indication of a
misbehaviour on the GMAC side, but most likely the issue stems from
the Motorcomm PHY.

While at it, drop the redundant gpio include, which is already provided
by jh7100-common.dtsi.

Co-developed-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Signed-off-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
 .../jh7100-starfive-visionfive-v1.dts         | 22 ++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts b/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
index e82af72f1aaf..4e396f820660 100644
--- a/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
+++ b/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
@@ -6,7 +6,6 @@
 
 /dts-v1/;
 #include "jh7100-common.dtsi"
-#include <dt-bindings/gpio/gpio.h>
 
 / {
 	model = "StarFive VisionFive V1";
@@ -18,3 +17,24 @@ gpio-restart {
 		priority = <224>;
 	};
 };
+
+/*
+ * The board uses a Motorcomm YT8521 PHY supporting RGMII-ID, but requires
+ * manual adjustment of the RX internal delay to work properly.  The default
+ * RX delay provided by the driver (1.95ns) is too high, but applying a 50%
+ * reduction seems to mitigate the issue.
+ *
+ * It is worth noting the adjustment is not necessary on BeagleV Starlight SBC,
+ * which uses a Microchip PHY.  Hence, most likely the Motorcomm PHY is the one
+ * responsible for the misbehaviour, not the GMAC.
+ */
+&mdio {
+	phy: ethernet-phy@0 {
+		reg = <0>;
+		rx-internal-delay-ps = <900>;
+	};
+};
+
+&gmac {
+	phy-handle = <&phy>;
+};
-- 
2.43.0

Cristian Ciocaltea wrote:
> The StarFive VisionFive V1 SBC uses a Motorcomm YT8521 PHY supporting
> RGMII-ID, but requires manual adjustment of the RX internal delay to
> work properly.
>
> The default RX delay provided by the driver is 1.95 ns, which proves to
> be too high. Applying a 50% reduction seems to mitigate the issue.
>
> Also note this adjustment is not necessary on BeagleV Starlight SBC,
> which uses a Microchip PHY.  Hence, there is no indication of a
> misbehaviour on the GMAC side, but most likely the issue stems from
> the Motorcomm PHY.
>
> While at it, drop the redundant gpio include, which is already provided
> by jh7100-common.dtsi.
>
> Co-developed-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
> Signed-off-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
> ---
>  .../jh7100-starfive-visionfive-v1.dts         | 22 ++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts b/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
> index e82af72f1aaf..4e396f820660 100644
> --- a/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
> +++ b/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
> @@ -6,7 +6,6 @@
>
>  /dts-v1/;
>  #include "jh7100-common.dtsi"
> -#include <dt-bindings/gpio/gpio.h>
>
>  / {
>  	model = "StarFive VisionFive V1";
> @@ -18,3 +17,24 @@ gpio-restart {
>  		priority = <224>;
>  	};
>  };
> +
> +/*
> + * The board uses a Motorcomm YT8521 PHY supporting RGMII-ID, but requires
> + * manual adjustment of the RX internal delay to work properly.  The default
> + * RX delay provided by the driver (1.95ns) is too high, but applying a 50%
> + * reduction seems to mitigate the issue.
> + *
> + * It is worth noting the adjustment is not necessary on BeagleV Starlight SBC,
> + * which uses a Microchip PHY.  Hence, most likely the Motorcomm PHY is the one
> + * responsible for the misbehaviour, not the GMAC.
> + */
> +&mdio {
> +	phy: ethernet-phy@0 {
> +		reg = <0>;
> +		rx-internal-delay-ps = <900>;
> +	};
> +};
> +
> +&gmac {
> +	phy-handle = <&phy>;
> +};

Alphabetical ordering here, please.

/Emil

On 12/20/23 15:48, Emil Renner Berthing wrote:
> Cristian Ciocaltea wrote:
>> The StarFive VisionFive V1 SBC uses a Motorcomm YT8521 PHY supporting
>> RGMII-ID, but requires manual adjustment of the RX internal delay to
>> work properly.
>>
>> The default RX delay provided by the driver is 1.95 ns, which proves to
>> be too high. Applying a 50% reduction seems to mitigate the issue.
>>
>> Also note this adjustment is not necessary on BeagleV Starlight SBC,
>> which uses a Microchip PHY.  Hence, there is no indication of a
>> misbehaviour on the GMAC side, but most likely the issue stems from
>> the Motorcomm PHY.
>>
>> While at it, drop the redundant gpio include, which is already provided
>> by jh7100-common.dtsi.
>>
>> Co-developed-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
>> Signed-off-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
>> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
>> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
>> ---
>>  .../jh7100-starfive-visionfive-v1.dts         | 22 ++++++++++++++++++-
>>  1 file changed, 21 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts b/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
>> index e82af72f1aaf..4e396f820660 100644
>> --- a/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
>> +++ b/arch/riscv/boot/dts/starfive/jh7100-starfive-visionfive-v1.dts
>> @@ -6,7 +6,6 @@
>>
>>  /dts-v1/;
>>  #include "jh7100-common.dtsi"
>> -#include <dt-bindings/gpio/gpio.h>
>>
>>  / {
>>  	model = "StarFive VisionFive V1";
>> @@ -18,3 +17,24 @@ gpio-restart {
>>  		priority = <224>;
>>  	};
>>  };
>> +
>> +/*
>> + * The board uses a Motorcomm YT8521 PHY supporting RGMII-ID, but requires
>> + * manual adjustment of the RX internal delay to work properly.  The default
>> + * RX delay provided by the driver (1.95ns) is too high, but applying a 50%
>> + * reduction seems to mitigate the issue.
>> + *
>> + * It is worth noting the adjustment is not necessary on BeagleV Starlight SBC,
>> + * which uses a Microchip PHY.  Hence, most likely the Motorcomm PHY is the one
>> + * responsible for the misbehaviour, not the GMAC.
>> + */
>> +&mdio {
>> +	phy: ethernet-phy@0 {
>> +		reg = <0>;
>> +		rx-internal-delay-ps = <900>;
>> +	};
>> +};
>> +
>> +&gmac {
>> +	phy-handle = <&phy>;
>> +};
> 
> Alphabetical ordering here, please.

Yeah, I wasn't sure if the ordering is more important than having the
referenced nodes added before.  I suppose there's a need for v6. :-)

> /Emil