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From: "Heiko Stübner" <heiko@sntech.de>
To: Dongjin Kim <tobetter@gmail.com>, Andrew Lunn <andrew@lunn.ch>
Cc: Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: dts: rockchip: Change ethernet TXD timing delay value
Date: Tue, 19 Aug 2025 20:44:26 +0200	[thread overview]
Message-ID: <2821088.9PvXe5no7K@diego> (raw)
In-Reply-To: <4d25c642-d457-4cb7-8bc1-587edd4f1d75@lunn.ch>

Am Dienstag, 19. August 2025, 18:03:47 Mitteleuropäische Sommerzeit schrieb Andrew Lunn:
> On Tue, Aug 19, 2025 at 01:50:17PM +0900, Dongjin Kim wrote:
> > Very poor network performance is observed on the ODROID-M1 Board
> > (REV 1.0 20220613) when running iperf3 (under 200Mbits/sec), and
> > this problem can be resolved after changing the value of TXD
> > timing to 0x35 from 0x4f.
> 
> How did you decide on 0x35?

just because I accidentially stumbled over that recently, Rockchip has
some scanning functionality in their vendor-kernel to get possible
delay values for a board.

Described in a document called "Rockchip GMAC RGMII Delayline Guide" [0]
and one code location is for example the armbian tree [1]

At least that is one possible source of per-board delay values :-)


Heiko


[0] https://lo01.g77k.com/aeb/docs/en/Common/GMAC/Rockchip_Developer_Guide_Linux_GMAC_RGMII_Delayline_EN.pdf
(random internet source Google found me)
[1] https://github.com/armbian/linux-rockchip/blob/rk-6.1-rkr5.1/drivers/net/ethernet/stmicro/stmmac/dwmac-rk-tool.c


> 
> ~/linux/arch/arm64$ grep -hr "tx_delay = " | sort | uniq -c
>       4 	tx_delay = <0x10>;
>       1 	tx_delay = <0x1a>;
>       1 	tx_delay = <0x21>;
>       2 	tx_delay = <0x22>;
>       4 	tx_delay = <0x24>;
>       2 	tx_delay = <0x26>;
>      14 	tx_delay = <0x28>;
>       1 	tx_delay = <0x2a>;
>       6 	tx_delay = <0x30>;
>       1 	tx_delay = <0x3a>;
>       3 	tx_delay = <0x3c>;
>       2 	tx_delay = <0x42>;
>       5 	tx_delay = <0x43>;
>       2 	tx_delay = <0x44>;
>       1 	tx_delay = <0x46>;
>       6 	tx_delay = <0x4f>;
> 
> The numbers are all over the place, but it is clear that 0x28 is the
> most popular for some reason. But since this delay values are magic,
> i've no idea why.
> 
>      Andrew
> 






WARNING: multiple messages have this Message-ID (diff)
From: "Heiko Stübner" <heiko@sntech.de>
To: Dongjin Kim <tobetter@gmail.com>, Andrew Lunn <andrew@lunn.ch>
Cc: Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: dts: rockchip: Change ethernet TXD timing delay value
Date: Tue, 19 Aug 2025 20:44:26 +0200	[thread overview]
Message-ID: <2821088.9PvXe5no7K@diego> (raw)
In-Reply-To: <4d25c642-d457-4cb7-8bc1-587edd4f1d75@lunn.ch>

Am Dienstag, 19. August 2025, 18:03:47 Mitteleuropäische Sommerzeit schrieb Andrew Lunn:
> On Tue, Aug 19, 2025 at 01:50:17PM +0900, Dongjin Kim wrote:
> > Very poor network performance is observed on the ODROID-M1 Board
> > (REV 1.0 20220613) when running iperf3 (under 200Mbits/sec), and
> > this problem can be resolved after changing the value of TXD
> > timing to 0x35 from 0x4f.
> 
> How did you decide on 0x35?

just because I accidentially stumbled over that recently, Rockchip has
some scanning functionality in their vendor-kernel to get possible
delay values for a board.

Described in a document called "Rockchip GMAC RGMII Delayline Guide" [0]
and one code location is for example the armbian tree [1]

At least that is one possible source of per-board delay values :-)


Heiko


[0] https://lo01.g77k.com/aeb/docs/en/Common/GMAC/Rockchip_Developer_Guide_Linux_GMAC_RGMII_Delayline_EN.pdf
(random internet source Google found me)
[1] https://github.com/armbian/linux-rockchip/blob/rk-6.1-rkr5.1/drivers/net/ethernet/stmicro/stmmac/dwmac-rk-tool.c


> 
> ~/linux/arch/arm64$ grep -hr "tx_delay = " | sort | uniq -c
>       4 	tx_delay = <0x10>;
>       1 	tx_delay = <0x1a>;
>       1 	tx_delay = <0x21>;
>       2 	tx_delay = <0x22>;
>       4 	tx_delay = <0x24>;
>       2 	tx_delay = <0x26>;
>      14 	tx_delay = <0x28>;
>       1 	tx_delay = <0x2a>;
>       6 	tx_delay = <0x30>;
>       1 	tx_delay = <0x3a>;
>       3 	tx_delay = <0x3c>;
>       2 	tx_delay = <0x42>;
>       5 	tx_delay = <0x43>;
>       2 	tx_delay = <0x44>;
>       1 	tx_delay = <0x46>;
>       6 	tx_delay = <0x4f>;
> 
> The numbers are all over the place, but it is clear that 0x28 is the
> most popular for some reason. But since this delay values are magic,
> i've no idea why.
> 
>      Andrew
> 





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  reply	other threads:[~2025-08-19 20:42 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-08-19  4:50 [PATCH] arm64: dts: rockchip: Change ethernet TXD timing delay value Dongjin Kim
2025-08-19  4:50 ` Dongjin Kim
2025-08-19  6:42 ` Krzysztof Kozlowski
2025-08-19  6:42   ` Krzysztof Kozlowski
2025-08-19  7:48   ` Dongjin Kim
2025-08-19  7:48     ` Dongjin Kim
2025-08-19 16:03 ` Andrew Lunn
2025-08-19 16:03   ` Andrew Lunn
2025-08-19 18:44   ` Heiko Stübner [this message]
2025-08-19 18:44     ` Heiko Stübner
2025-08-20  2:45   ` Dongjin Kim
2025-08-20  2:45     ` Dongjin Kim
2025-09-03 16:10     ` Stefan Monnier

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