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([39.170.101.209]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-38f6413fe85sm1376399a91.12.2026.07.28.06.22.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2026 06:22:35 -0700 (PDT) From: Zxyan Zhu To: maxime.chevallier@bootlin.com Cc: andrew+netdev@lunn.ch, rmk+kernel@armlinux.org.uk, alexandre.torgue@foss.st.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, hkallweit1@gmail.com, mcoquelin.stm32@gmail.com, netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v2] net: phylink: add phylink_pcs_loopback() method for PCS loopback support Date: Tue, 28 Jul 2026 21:22:27 +0800 Message-Id: <20260728132227.4051026-1-zxyan0222@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <2c0c6864-99ea-48d6-a889-c886bb91c351@bootlin.com> References: <2c0c6864-99ea-48d6-a889-c886bb91c351@bootlin.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, Jul 28, 2026 at 10:41:12AM +0200, Maxime Chevallier wrote: > I'm actually seriously wondering if we shouldn't just stick to MAC > loopback only for stmmac selftests. [...] > Using an external loopback (in PCS, in PHY, somewhere else...) doesn't > bring anything to the table given what we are testing today, which is > internal stmmac behaviour. The MAC loopback happens at the GMII level, > so everything we are currently testing happens before that. You're right. MAC loopback at the GMII level already covers everything stmmac selftests actually test (DMA, filtering, VLAN, checksum offload, etc.). PCS acts only as external transceivers beyond the MAC boundary and do not bring additional test coverage. Given that, I will drop this PCS loopback patch series. Thanks for the explanation! Zxyan