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[83.28.84.81]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e71ba24f6sm2853609f8f.51.2026.10.30.05.05.35 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Fri, 30 Oct 2026 05:05:36 -0700 (PDT) Date: Fri, 30 Oct 2026 13:05:32 +0100 From: Michal Pecio To: Mathias Nyman Cc: Greg KH , linux-usb@vger.kernel.org, regressions@lists.linux.dev, Yiyu Zhou , Dennis Wissel Subject: Re: [PATCH v2] xhci: give back TDs and clean up ep0 after disconnect Message-ID: <20261030130532.36a75025.michal.pecio@gmail.com> In-Reply-To: References: <20261029204324.658845-1-mathias.nyman@linux.intel.com> <20261029204324.658845-2-mathias.nyman@linux.intel.com> <2026103009-handful-labored-d1ce@gregkh> X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 30 Oct 2026 13:05:16 +0200, Mathias Nyman wrote: > > And sashiko seems to object to it, is that response correct? > > > > It does find one potential case where this patch does not fix the > enumeration of devices that disconnect during reset. Honestly, is this 7.3 code being fixed here reliable at all? As Sashiko points out (and I did before), we are 100% at the mercy of hardware and USB core with those "connected" and "link error" flags. Sashiko thinks that we may fail to clear these flags in some cases. Is it guaranteed that we can't clear them prematurely at other times? If USB3 link comes back after core has cleared all status change bits (brief disconnection), we will get another Port Status Change Event, observe the port in "Connected/U0" state and reset these flags. Is it guaranteed that core won't clear change bits until it finishes disconnection of affected devices so that all URBs are unlinked and we can no longer run into those HW bugs anymore? If this fails to work, it's another regression vs 7.2 and prior. The old VDEV_PORT_ERROR flag used to stick for device lifetime. And it could have been extended to all disconnected devices, not just the one directly attached to the root port, to fix disconnection of whole trees with hubs while avoiding the above race condition. The reported USB2 regressions would have also been avoided, because old code only applied to USB3 ports and there is no actual need to generalize it to USB2 at this time. The bug still affected USB3, but it seems nobody uses USB3 devices that trigger it. I suppose I could fix the Renesas disconnection issue which the 7.3 rework tried to address with an alternative patch smaller than this fixup, provided that the whole series is reverted. The preexisting USB3 bug would remain unsolved for now, however. Regards, Michal