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 A40F83A29E for ; Fri, 1 Mar 2024 19:09:36 +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=1709320176; cv=none; b=dquug33psv5cw6wjAQb322bSjyGMZ0Dn1bLtxQr6jL7VSbPe2Glrx8sxqguFesUqmZIb7KQ0w7fZptNfxZTso9QuF+4vpJbEcWy1lyhEvSEcZthhMDMK1rLRwLwtEl2dB1JhxxTZnxfWG75o9JyjdbNLTWDS/Tp4XxH4lO8LwwU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709320176; c=relaxed/simple; bh=gGaw7n6HkcI9Dwb9fl4ftknPfprEKaRmQYJUVWKyX9Q=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: Content-Type:MIME-Version; b=aIljcX3lNLPkpsp1nLuQUKiraMSMR4kwQEwHO6haaySk9LiGiHA6vmvvHNLu2kt6f3I9WhDdxVbnzMb/Dx/a2KibTyz1i5hmcQbePF2q1LEbt6ChswlZ9VrGnnpS7mVgnMHTlYrMqc7IhP6MBpuaXjiIC5TU/0Bht7Y8fYwLtSE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kZzOzNMM; 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="kZzOzNMM" Received: by smtp.kernel.org (Postfix) with ESMTPS id 227D5C433B2 for ; Fri, 1 Mar 2024 19:09:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1709320176; bh=gGaw7n6HkcI9Dwb9fl4ftknPfprEKaRmQYJUVWKyX9Q=; h=From:To:Subject:Date:In-Reply-To:References:From; b=kZzOzNMMyZ7q9R7YxmfsoQie7BV3wvdQ9QK41uIOvtQkfz2nHOM2ehUjoF0+JBRik ThTrddKLnVPRupPiYBLy06RJgt5rqz0rY1Yzo+uqSWJAsdv0KLklm6aJ+duAWzTkZX E+8KQfNlRRm9t+fVxDaXczraafuPSWT7n9hm78ZO/wo+KnrIywmogh/YzfH/W1NugA wqTOyQAxvMcjrEKUzBFu6Tz+Gw8cjLQN14nBcdFZAbsjq69FBybV9Sx9jiLWXD4qEd /creVsKAHIV1hvqFujnldxb2RJcoecL1m4DJIoZWT+NGvxuFVkhb0nFC+A3rYcW3FT 8THuwofMvg5zg== Received: by aws-us-west-2-korg-bugzilla-1.web.codeaurora.org (Postfix, from userid 48) id 10849C53BD0; Fri, 1 Mar 2024 19:09:36 +0000 (UTC) From: bugzilla-daemon@kernel.org To: linux-usb@vger.kernel.org Subject: [Bug 218544] not enough bandwidth, synaptics hi-res audio duplex audio Date: Fri, 01 Mar 2024 19:09:35 +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: stern@rowland.harvard.edu 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: cc 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=3D218544 Alan Stern (stern@rowland.harvard.edu) changed: What |Removed |Added ---------------------------------------------------------------------------- CC|stern@rowland.harvard.edu | --- Comment #7 from Alan Stern (stern@rowland.harvard.edu) --- There's also the usbhid interface on the audio device, probably used for a volume control or something like that. Maybe unbinding it too will help. = You can try it, anyway, just to see what happens: echo 1-1.1:1.3 >/sys/bus/usb/drivers/usbhid/unbind (or with the device plugged into the rear port, use 2-1.1:1.3). Without going into any deeper testing, I can summarize the problem for you.= =20 Basically, the ehci-hcd driver in Linux has trouble utilizing the entire available bandwidth when low- or full-speed (1.5 or 12 Mb/s) devices are connected via a USB-2 hub. That's your situation; the hub is the 1-1 (or 2= -1) device, number 002 on both buses. At one time Intel's chipsets would attach a single onboard hub directly to = the EHCI controller and then connect all the downstream USB ports through that = hub.=20 This is what your laptop has. Even earlier Intel chipsets worked different= ly; they connected each downstream USB port through a switch which would send high-speed signals to the EHCI controller and low/full-speed signals to a companion UHCI controller. Motherboards using that scheme didn't suffer fr= om this bandwidth problem unless the user connected a full/low-speed device vi= a an external USB-2 hub. The reason for the problem is that the design of USB 2.0 and the EHCI controller hardware make it quite complicated to handle the packet scheduli= ng when translating between two different speeds on the same bus. The driver = uses an incomplete and imperfect algorithm which can handle the simplest cases o= kay but is not adequate for situations requiring a higher percentage of the tot= al bandwidth, especially when different transfer types (bulk, interrupt, and isochronous) are mixed. Improving the driver to make it more capable would require a tremendous amo= unt of work, and for very little return since nowadays computers use xHCI USB controllers rather than EHCI. Only legacy systems dating from the time of = your T420 laptop or earlier would derive any benefit, and then only in situations involving multiple devices with high bandwidth requirements. I hope this explanation makes sense to you. --=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.=