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[73.214.169.22]) by smtp.gmail.com with ESMTPSA id c5-20020a5b0145000000b00bb144da7d68sm905217ybp.13.2023.06.09.07.29.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Jun 2023 07:29:18 -0700 (PDT) Date: Fri, 9 Jun 2023 10:29:16 -0400 From: Brian Masney To: Andrew Halaney Cc: linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, netdev@vger.kernel.org, linux-arm-msm@vger.kernel.org, konrad.dybcio@linaro.org, andersson@kernel.org, agross@kernel.org, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org, richardcochran@gmail.com, echanude@redhat.com Subject: Re: [PATCH] arm64: dts: qcom: sa8540p-ride: Specify ethernet phy OUI Message-ID: References: <20230608201513.882950-1-ahalaney@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230608201513.882950-1-ahalaney@redhat.com> User-Agent: Mutt/2.2.9 (2022-11-12) Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Thu, Jun 08, 2023 at 03:15:13PM -0500, Andrew Halaney wrote: > With wider usage on more boards, there have been reports of the > following: > > [ 315.016174] qcom-ethqos 20000.ethernet eth0: no phy at addr -1 > [ 315.016179] qcom-ethqos 20000.ethernet eth0: __stmmac_open: Cannot attach to PHY (error: -19) > > which has been fairly random and isolated to specific boards. > Early reports were written off as a hardware issue, but it has been > prevalent enough on boards that theory seems unlikely. > > In bring up of a newer piece of hardware, similar was seen, but this > time _consistently_. Moving the reset to the mdio bus level (which isn't > exactly a lie, it is the only device on the bus so one could model it as > such) fixed things on that platform. Analysis on sa8540p-ride shows that > the phy's reset is not being handled during the OUI scan if the reset > lives in the phy node: > > # gpio 752 is the reset, and is active low, first mdio reads are the OUI > modprobe-420 [006] ..... 154.738544: mdio_access: stmmac-0 read phy:0x08 reg:0x02 val:0x0141 > modprobe-420 [007] ..... 154.738665: mdio_access: stmmac-0 read phy:0x08 reg:0x03 val:0x0dd4 > modprobe-420 [004] ..... 154.741357: gpio_value: 752 set 1 > modprobe-420 [004] ..... 154.741358: gpio_direction: 752 out (0) > modprobe-420 [004] ..... 154.741360: gpio_value: 752 set 0 > modprobe-420 [006] ..... 154.762751: gpio_value: 752 set 1 > modprobe-420 [007] ..... 154.846857: gpio_value: 752 set 1 > modprobe-420 [004] ..... 154.937824: mdio_access: stmmac-0 write phy:0x08 reg:0x0d val:0x0003 > modprobe-420 [004] ..... 154.937932: mdio_access: stmmac-0 write phy:0x08 reg:0x0e val:0x0014 > > Moving it to the bus level, or specifying the OUI in the phy's > compatible ensures the reset is handled before any mdio access > Here is tracing with the OUI approach (which skips scanning the OUI): > > modprobe-549 [007] ..... 63.860295: gpio_value: 752 set 1 > modprobe-549 [007] ..... 63.860297: gpio_direction: 752 out (0) > modprobe-549 [007] ..... 63.860299: gpio_value: 752 set 0 > modprobe-549 [004] ..... 63.882599: gpio_value: 752 set 1 > modprobe-549 [005] ..... 63.962132: gpio_value: 752 set 1 > modprobe-549 [006] ..... 64.049379: mdio_access: stmmac-0 write phy:0x08 reg:0x0d val:0x0003 > modprobe-549 [006] ..... 64.049490: mdio_access: stmmac-0 write phy:0x08 reg:0x0e val:0x0014 > > The OUI approach is taken given the description matches the situation > perfectly (taken from ethernet-phy.yaml): > > - pattern: "^ethernet-phy-id[a-f0-9]{4}\\.[a-f0-9]{4}$" > description: > If the PHY reports an incorrect ID (or none at all) then the > compatible list may contain an entry with the correct PHY ID > in the above form. > The first group of digits is the 16 bit Phy Identifier 1 > register, this is the chip vendor OUI bits 3:18. The > second group of digits is the Phy Identifier 2 register, > this is the chip vendor OUI bits 19:24, followed by 10 > bits of a vendor specific ID. > > With this in place the sa8540p-ride's phy is probing consistently, so > it seems the floating reset during mdio access was the issue. In either > case, it shouldn't be floating so this improves the situation. The below > link discusses some of the relationship of mdio, its phys, and points to > this OUI compatible as a way to opt out of the OUI scan pre-reset > handling which influenced this decision. > > Link: https://lore.kernel.org/all/dca54c57-a3bd-1147-63b2-4631194963f0@gmail.com/ > Fixes: 57827e87be54 ("arm64: dts: qcom: sa8540p-ride: Add ethernet nodes") > Signed-off-by: Andrew Halaney Reviewed-by: Brian Masney