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[83.28.42.48]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-539ffff38fcsm232689e87.121.2024.10.15.11.52.33 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Tue, 15 Oct 2024 11:52:34 -0700 (PDT) Date: Tue, 15 Oct 2024 20:52:30 +0200 From: =?UTF-8?B?TWljaGHFgg==?= Pecio To: Greg KH Cc: Mathias Nyman , linux-usb@vger.kernel.org Subject: Re: [PATCH 2/2] usb: xhci: Warn about suspected "start-stop" bugs in HCs Message-ID: <20241015205230.622edcc7@foxbook> In-Reply-To: <2024101534-roundup-promotion-eb13@gregkh> References: <20241014210840.5941d336@foxbook> <20241014211122.7cb5b133@foxbook> <2024101534-roundup-promotion-eb13@gregkh> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Hi, > + if (!(xhci->quirks & XHCI_NEC_HOST)) { > > + xhci_warn(xhci, "Unhandled Stop Endpoint failure on slot %d ep_index %d\n", > > + slot_id, ep_index); > > If a user sees this, what are they supposed to do? This is a hardware > bug, but with this we are going to get reports of "something broke in > the kernel", right? Why not make it just more informative, like: > xhci_info(xhci, "hardware can not deal with... > > or something like that so that people know we know about the bug, and > are working around it, but that it's not our issue, but rather the > hardware that is at fault? Yes, the point is that ideally some users would report when they see it. This is not a warning for a bug we know about and work around, it's for hypothetical bugs that aren't known. If I'm adding code to handle a bug of my HC, I might as well use it to sanity check other HCs for free. Ideally they are OK and no one will ever see it. I tested several HCs in January and found no similar issues. Maybe I will test them again. I specifically worded it as something the kernel could do better rather than the kernel just whining about something incomprehensibly. For the latter, we already have the absolute classic "ERROR Transfer event TRB DMA ptr not part of current TD", which would often follow this one, but offer little clue about the root cause. It's kinda too late by then. Regards, Michal