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Tue, 19 Aug 2025 19:45:34 -0700 (PDT) Received: from anyang ([106.250.177.234]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-245ed53caacsm10765625ad.159.2025.08.19.19.45.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Aug 2025 19:45:34 -0700 (PDT) Date: Wed, 20 Aug 2025 11:45:29 +0900 From: Dongjin Kim To: Andrew Lunn Cc: Rob Herring , Krzysztof Kozlowski , Heiko Stuebner , 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 Message-ID: References: <20250819045018.2094282-1-tobetter@gmail.com> <4d25c642-d457-4cb7-8bc1-587edd4f1d75@lunn.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4d25c642-d457-4cb7-8bc1-587edd4f1d75@lunn.ch> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250819_194535_797111_7E626E1B X-CRM114-Status: GOOD ( 17.52 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Aug 19, 2025 at 06:03:47PM +0200, Andrew Lunn wrote: > 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? > > ~/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 I do have more numbers in the Rockchip BSP kernel, and 0x35 is from one of them that shows less retry counts when testing 'iperf3' while testing with the batch of ODROID-M1. :) Thanks, Dongjin Kim.