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[83.173.201.248]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-63e7ef95e81sm5781449a12.21.2025.10.27.02.18.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Oct 2025 02:18:41 -0700 (PDT) Message-ID: Date: Mon, 27 Oct 2025 10:18:40 +0100 Precedence: bulk X-Mailing-List: imx@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64: dts: imx8mp-debix-model-a: Disable EEE for 1000T To: "Russell King (Oracle)" Cc: Laurent Pinchart , Andrew Lunn , devicetree@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, Daniel Scally , Kieran Bingham , Stefan Klug , Conor Dooley , Fabio Estevam , Krzysztof Kozlowski , Pengutronix Kernel Team , Rob Herring , Sascha Hauer , Shawn Guo , Emanuele Ghidoli References: <20251026122905.29028-1-laurent.pinchart@ideasonboard.com> <20251027072749.GA7811@pendragon.ideasonboard.com> <341f56de-9dde-4c44-9542-b523e1917dcb@gmail.com> Content-Language: en-US From: Emanuele Ghidoli In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 27/10/2025 10:00, Russell King (Oracle) wrote: > On Mon, Oct 27, 2025 at 09:47:53AM +0100, Emanuele Ghidoli wrote: >> On 27/10/2025 08:27, Laurent Pinchart wrote: >>> Hi Andrew, >>> >>> Thank you for your quick reply. >>> >>> On Mon, Oct 27, 2025 at 04:08:42AM +0100, Andrew Lunn wrote: >>>> Adding Russell King >>>> >>>> On Sun, Oct 26, 2025 at 02:29:04PM +0200, Laurent Pinchart wrote: >>>>> Energy Efficient Ethernet (EEE) is broken at least for 1000T on the EQOS >>>>> (DWMAC) interface. When connected to an EEE-enabled peer, the ethernet >>>>> devices produces an interrupts storm. Disable EEE support to fix it. >>>>> >>>>> Signed-off-by: Laurent Pinchart >>>>> --- >>>>> The exact reason for the interrupt storm is unknown, and my attempts to >>>>> diagnose it was hindered by my lack of expertise with DWMAC. As far as I >>>>> understand, the DWMAC implements EEE support, and so does the RTL8211E >>>>> PHY according to its datasheet. >>>> >>>> I believe for DWMAC it is a synthesis option. However, there is a bit >>>> indicating if the hardware supports it. >>>> >>>> The PHY should not be able to trigger an interrupt storm in the >>>> MAC. So this is likely to be an DWMAC issue. >>>> >>>> Which interrupt bit is causing the storm? >>> >>> That's where I hit my first wall :-) >>> >>> I've tried to diagnose the issue by adding interrupt counters to >>> dwmac4_irq_status(), counting interrupts for each bit of GMAC_INT_STATUS >>> (0x00b0). Bit RGSMIIIS (0) is the only one that seems linked to the >>> interrupts storm, increasing at around 10k per second. However, the >>> corresponding bit in GMAC_INT_EN (0x00b4) is *not* set. >>> >>> The ENET_EQOS interrupt on the i.MX8MP is an OR'ed signal that combines >>> four interrupt sources: >>> >>> - ENET QOS TSN LPI RX exit Interrupt >>> - ENET QOS TSN Host System Interrupt >>> - ENET QOS TSN Host System RX Channel Interrupts >>> - ENET QOS TSN Host System TX Channel Interrupts >>> >>> The last two interrupt sources are themselves local OR of channels[4:0]. >>> >>> I ould suspect that the LPI RX exit interrupt is the one that fires >>> constantly given its name, but I'm not sure how to test that. >>> >>>>> What each side does exactly is unknown >>>>> to me. One theory I've heard to explain the issue is that the two >>>>> implementations conflict. There is no register in the RTL8211E PHY to >>>>> disable EEE on the PHY side while still advertising its support to the >>>>> peer and relying on the implementation in the DWMAC (if this even makes >>>>> sense) >>>> >>>> It does not make sense. EEE is split into two major parts. The two >>>> PHYs communicate with each other to negotiate the feature, if both >>>> ends support it and both ends want to use it. The result of this >>>> negotiation is then passed to the MACs. >>>> >>>> It is then the MAC who decides when to send a Low Power Indication to >>>> the PHY to tell the PHY to enter low power mode. The MAC also wakes >>>> the PHY when it has packets to send. >>>> >>>> A quick look at the data sheet for the RTL8211E suggests this is what >>>> is supports. >>>> >>>> There are a few PHYs which implement SmartEEE, or some other similar >>>> name. They operate differently, the PHY does it all, and the MAC is >>>> not even aware EEE is happening. Such PHYs should really only be >>>> paired with MACs which do not support EEE. An EEE capable MAC paired >>>> with a SmartEEE PHY could have problems, but hopefully the EEE >>>> abilities and negotiation registers in the PHY would be sufficient to >>>> dissuade the MAC from doing EEE. But i would not expect a setup like >>>> this to trigger an interrupt storm. >>> >>> Thanks for the explanation, I read documents to try and figure out how >>> it worked and didn't find such a clear and concise high-level summary. >>> >>> I'm not very experienced with ethernet, but I can easily test patches or >>> even rough ideas on hardware. >>> >> >> Hi Laurent, >> I had the same problem, interrupt storm plus link instability with dwmac. > > You never said that in your patch description. You said "it causes > link instability and communication failures." Have you investigated > what the cause of the interrupt storm is? > >> I found out that 2c81f3357136 ("net: stmmac: convert to phylink PCS support") >> commit is the one causing the problem to me. The correct commit is 4218647d4556 (“net: stmmac: convert to phylink managed EEE support”).> > You claim this commit enables EEE by default. It does. However, stmmac > _before_ this commit enables EEE by default as I've already explained, > quoting the old code which effects this. I've asked you to test > further. So far, I've heard nothing back. > > What has changed is that we no longer do anything with the RGSMIIS > status, and in theory keep the mask/enable for this disabled. Howeer, > that is a subsequent commit. > Hi Russell, Sorry, I made a copy-and-paste mistake earlier. I identified it through a bisect, and reverting this commit (or disabling EEE) resolves the issue I’m seeing. I’m continuing to investigate further to understand the root cause.