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Subject: Re: [PATCH] arm64: dts: rockchip: Add txpbl node for RK3399/RK3328
To:     Carlos de Paula <me@carlosedp.com>
Cc:     papadakospan@gmail.com, jose.abreu@synopsys.com,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Heiko Stuebner <heiko@sntech.de>,
        Robin Murphy <robin.murphy@arm.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Peter Geis <pgwipeout@gmail.com>,
        Katsuhiro Suzuki <katsuhiro@katsuster.net>,
        Johan Jonker <jbx6244@gmail.com>,
        Philipp Tomsich <philipp.tomsich@theobroma-systems.com>,
        Christoph Muellner <christoph.muellner@theobroma-systems.com>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20200218221040.10955-1-me@carlosedp.com>
From:   Daniel Lezcano <daniel.lezcano@linaro.org>
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Message-ID: <6f0447c7-0d84-fd63-61e3-b470c1b49172@linaro.org>
Date:   Sun, 1 Mar 2020 09:22:41 +0100
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On 18/02/2020 23:10, Carlos de Paula wrote:
> Some rockchip SoCs like the RK3399 and RK3328 exhibit an issue
> where tx checksumming does not work with packets larger than 1498.
> 
> The default Programmable Buffer Length for TX in these GMAC's is
> not suitable for MTUs higher than 1498. The workaround is to disable
> TX offloading with 'ethtool -K eth0 tx off rx off' causing performance
> impacts as it disables hardware checksumming.
> 
> This patch sets snps,txpbl to 0x4 which is a safe number tested ok for
> the most popular MTU value of 1500.

I don't know what this option says, why not specify a mtu in the DT?

The hardware limitation will be more clear, no?

> For reference, see https://lkml.org/lkml/2019/4/1/1382.
> 
> Signed-off-by: Carlos de Paula <me@carlosedp.com>
> ---
>  arch/arm64/boot/dts/rockchip/rk3328.dtsi | 2 ++
>  arch/arm64/boot/dts/rockchip/rk3399.dtsi | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/rockchip/rk3328.dtsi b/arch/arm64/boot/dts/rockchip/rk3328.dtsi
> index 1f53ead52c7f..b7f1de4b7fd0 100644
> --- a/arch/arm64/boot/dts/rockchip/rk3328.dtsi
> +++ b/arch/arm64/boot/dts/rockchip/rk3328.dtsi
> @@ -906,6 +906,7 @@
>  		resets = <&cru SRST_GMAC2IO_A>;
>  		reset-names = "stmmaceth";
>  		rockchip,grf = <&grf>;
> +		snps,txpbl = <0x4>;
>  		status = "disabled";
>  	};
>  
> @@ -913,6 +914,7 @@
>  		compatible = "rockchip,rk3328-gmac";
>  		reg = <0x0 0xff550000 0x0 0x10000>;
>  		rockchip,grf = <&grf>;
> +		snps,txpbl = <0x4>;
>  		interrupts = <GIC_SPI 21 IRQ_TYPE_LEVEL_HIGH>;
>  		interrupt-names = "macirq";
>  		clocks = <&cru SCLK_MAC2PHY_SRC>, <&cru SCLK_MAC2PHY_RXTX>,
> diff --git a/arch/arm64/boot/dts/rockchip/rk3399.dtsi b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> index 33cc21fcf4c1..cd5415d7e559 100644
> --- a/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> +++ b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> @@ -288,6 +288,7 @@
>  		resets = <&cru SRST_A_GMAC>;
>  		reset-names = "stmmaceth";
>  		rockchip,grf = <&grf>;
> +		snps,txpbl = <0x4>;
>  		status = "disabled";
>  	};
>  
> 


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