From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0660852F88 for ; Sat, 8 Nov 2025 10:33:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762598007; cv=none; b=uHw5U45+qj4HhOskNZCoqvPAdrAExz10vVPpFAwKB31hySu4UVxvlJ9meMs+eeKS6qevHPwjtp7x8c8UOIuoT0Q8ap0xiWUdpwsKDPl1rIAZtvSPk7U/W3AtdObFQllvtyB2iGFNhqJwM3GYYIqGFpxzRbQGdYrZw4xPHjxSwY4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762598007; c=relaxed/simple; bh=C1yXKPZgb2S9PSsK3zvNL5FfiC6VnN8klum5fWbs7y4=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: Content-Type:MIME-Version; b=ORVjpJ2KGs9iOYqMIqeokuz4Crqzn5T/vdjmukm8//hcoEA/9visGLPVyLNu0ybgejTiNWdZuj1Oi9I/4QavaO3NAZLtUUfqKN382fixqc+lZvq+HYHwu+E50TYLfVleT949yiR4ZB0sx2Klw9oJSZeykbJ0blkJ4sybXmBCSJU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AZY5nldi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AZY5nldi" Received: by smtp.kernel.org (Postfix) with ESMTPS id 8A4E9C4CEF5 for ; Sat, 8 Nov 2025 10:33:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762598006; bh=C1yXKPZgb2S9PSsK3zvNL5FfiC6VnN8klum5fWbs7y4=; h=From:To:Subject:Date:In-Reply-To:References:From; b=AZY5nldiyS5bx1dRLiKOpUMlW2aGBCkAwJ42XWItk/aCfbPV6xtNRHD77YKgWzGru ZSYg7yonYXUIkZRg76cgrtgfuFtBYVOSpQKm3d2xG8EgrcFuYRgEv5KPZwxfrcAHIr 2itZoGase5BZcOqlXoFMKRUWtOX6OEqXA/KmufR/tHdSAAQzjHaTohoA6ZOnOi5XPh 0GWtR26bwxqIJBvwvQYaB3yHLJ6Dp3WOe+S6vvG2iqMsB03i+PH9eIv0Te9NHGyCSW klqpVlDvW0dqx6d/hrlTHdtFPpfWnt/HClp53F7TqIqosmoIPRdDicbWEqh/8arji9 UXf9dU1xV2j1w== Received: by aws-us-west-2-korg-bugzilla-1.web.codeaurora.org (Postfix, from userid 48) id 85992C41613; Sat, 8 Nov 2025 10:33:26 +0000 (UTC) From: bugzilla-daemon@kernel.org To: linux-usb@vger.kernel.org Subject: [Bug 220748] usb: xhci_queue_isoc_tx_prepare ignore start_frame and always assumes URB_ISO_ASAP is set Date: Sat, 08 Nov 2025 10:33:26 +0000 X-Bugzilla-Reason: None X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: AssignedTo drivers_usb@kernel-bugs.kernel.org X-Bugzilla-Product: Drivers X-Bugzilla-Component: USB X-Bugzilla-Version: 2.5 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: michal.pecio@gmail.com X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: drivers_usb@kernel-bugs.kernel.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugzilla.kernel.org/ Auto-Submitted: auto-generated Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 https://bugzilla.kernel.org/show_bug.cgi?id=3D220748 --- Comment #14 from Micha=C5=82 Pecio (michal.pecio@gmail.com) --- I skimmed the linked forum thread and it seems the issue is not so much with "needing a specific frame interval", but not tolerating any missing packets. https://linuxmusicians.com/viewtopic.php?p=3D177688#p177688 So no-gaps scheduling is already the default *without* URB_ISO_ASAP and dri= vers don't need to fill sequential frame IDs themselves if that's what they want. Note that this stops working when the queue underruns - next URB is assumed= to be a new stream and will be scheduled into the future, not into the past. If there are gaps despite the driver resubmitting on time, that may be a bu= g, but a different one than originally assumed. If drivers want to insert a gap to resynchronize after detected lost packet= s, I'm afraid that's not supported in the current model. It would be technical= ly possible on CFC xHCI hosts and likely EHCI. A concern is how drivers would = know when frame ID overflows back to zero and how much into the future they can schedule. The urb->start_frame field is now output, so drivers can use it to confirm = if the URBs are scheduled sequentially as intended. At least with CFC, it appe= ars that these numbers should be consistent with reality, though I have never tested it. Debugfs/tracing/printk may be used to check them against TRBs written to the HW. Non-CFC looks weird, maybe it could be improved somewhat but not sure. The = old xHCI 1.0 spec is limited in what it guarantees. --=20 You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.=