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 041123081A8; Mon, 13 Oct 2025 14:56:32 +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=1760367392; cv=none; b=u+zMPWLjwtRZonOIDNtGMcVRg1iG+U1aMwHe0UtW55W0/e4rRK2cRjlwtlM3nthBQapzbJyzc58rur7tk0Lo06i2KIePbxjL4q8Fi0krW/DGM3eH0WAihnnJK9tPpr/QyMG8CyAMUzKMebRU6KGfk2j7ACmjgQ9bHttkjOL+FF4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760367392; c=relaxed/simple; bh=dlAHIWq7AeTcknK8hxTo6DjKYQH8jXOuMJS06zZ0LCE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=MURyljUDqXz2jfWhQdu4VuFBaX8MJdOyjhvmOD2i6+BKo9H+vUOW4sbeXGcBL0mQzrTMFtMBAKK7jWgeVWOa6VjpmD9kJU7wCLzCrxjx6s6Hc62l10XVXoKFi0fH4hTMl7h9fZEsS8ZxGCbRIZL112e5OYQt6TyMjbI3mlNpY+w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qKxH0vOg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="qKxH0vOg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B48EC4CEE7; Mon, 13 Oct 2025 14:56:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1760367391; bh=dlAHIWq7AeTcknK8hxTo6DjKYQH8jXOuMJS06zZ0LCE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qKxH0vOghs2Ag+X+WMu8joT76ExJdjbbduN1/P2INIXMk3ow0xOBVoBJIoFPAnoPh wGZlTxnd8XmwbBbugjOP+Yn+AzS1Azv7F4aRy8d2NVibLQx9u2YvVke8JGu6fE1fuJ B+CCTuyjmpHCpRIPOhY34v0epXFpdIo6tGtmyJ3w= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Hubert=20Wi=C5=9Bniewski?= , Marek Szyprowski , Oleksij Rempel , Paolo Abeni Subject: [PATCH 6.1 191/196] net: usb: asix: hold PM usage ref to avoid PM/MDIO + RTNL deadlock Date: Mon, 13 Oct 2025 16:46:04 +0200 Message-ID: <20251013144321.600758432@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251013144314.549284796@linuxfoundation.org> References: <20251013144314.549284796@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleksij Rempel commit 3d3c4cd5c62f24bb3cb4511b7a95df707635e00a upstream. Prevent USB runtime PM (autosuspend) for AX88772* in bind. usbnet enables runtime PM (autosuspend) by default, so disabling it via the usb_driver flag is ineffective. On AX88772B, autosuspend shows no measurable power saving with current driver (no link partner, admin up/down). The ~0.453 W -> ~0.248 W drop on v6.1 comes from phylib powering the PHY off on admin-down, not from USB autosuspend. The real hazard is that with runtime PM enabled, ndo_open() (under RTNL) may synchronously trigger autoresume (usb_autopm_get_interface()) into asix_resume() while the USB PM lock is held. Resume paths then invoke phylink/phylib and MDIO, which also expect RTNL, leading to possible deadlocks or PM lock vs MDIO wake issues. To avoid this, keep the device runtime-PM active by taking a usage reference in ax88772_bind() and dropping it in unbind(). A non-zero PM usage count blocks runtime suspend regardless of userspace policy (.../power/control - pm_runtime_allow/forbid), making this approach robust against sysfs overrides. Holding a runtime-PM usage ref does not affect system-wide suspend; system sleep/resume callbacks continue to run as before. Fixes: 4a2c7217cd5a ("net: usb: asix: ax88772: manage PHY PM from MAC") Reported-by: Hubert Wiśniewski Closes: https://lore.kernel.org/all/DCGHG5UJT9G3.2K1GHFZ3H87T0@gmail.com Tested-by: Hubert Wiśniewski Reported-by: Marek Szyprowski Closes: https://lore.kernel.org/all/b5ea8296-f981-445d-a09a-2f389d7f6fdd@samsung.com Cc: stable@vger.kernel.org Signed-off-by: Oleksij Rempel Link: https://patch.msgid.link/20251005081203.3067982-1-o.rempel@pengutronix.de Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman --- drivers/net/usb/asix_devices.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) --- a/drivers/net/usb/asix_devices.c +++ b/drivers/net/usb/asix_devices.c @@ -625,6 +625,21 @@ static void ax88772_suspend(struct usbne asix_read_medium_status(dev, 1)); } +/* Notes on PM callbacks and locking context: + * + * - asix_suspend()/asix_resume() are invoked for both runtime PM and + * system-wide suspend/resume. For struct usb_driver the ->resume() + * callback does not receive pm_message_t, so the resume type cannot + * be distinguished here. + * + * - The MAC driver must hold RTNL when calling phylink interfaces such as + * phylink_suspend()/resume(). Those calls will also perform MDIO I/O. + * + * - Taking RTNL and doing MDIO from a runtime-PM resume callback (while + * the USB PM lock is held) is fragile. Since autosuspend brings no + * measurable power saving here, we block it by holding a PM usage + * reference in ax88772_bind(). + */ static int asix_suspend(struct usb_interface *intf, pm_message_t message) { struct usbnet *dev = usb_get_intfdata(intf); @@ -922,6 +937,13 @@ static int ax88772_bind(struct usbnet *d if (ret) goto initphy_err; + /* Keep this interface runtime-PM active by taking a usage ref. + * Prevents runtime suspend while bound and avoids resume paths + * that could deadlock (autoresume under RTNL while USB PM lock + * is held, phylink/MDIO wants RTNL). + */ + pm_runtime_get_noresume(&intf->dev); + return 0; initphy_err: @@ -951,6 +973,8 @@ static void ax88772_unbind(struct usbnet phylink_destroy(priv->phylink); ax88772_mdio_unregister(priv); asix_rx_fixup_common_free(dev->driver_priv); + /* Drop the PM usage ref taken in bind() */ + pm_runtime_put(&intf->dev); } static void ax88178_unbind(struct usbnet *dev, struct usb_interface *intf) @@ -1575,6 +1599,11 @@ static struct usb_driver asix_driver = { .resume = asix_resume, .reset_resume = asix_resume, .disconnect = usbnet_disconnect, + /* usbnet enables autosuspend by default (supports_autosuspend=1). + * We keep runtime-PM active for AX88772* by taking a PM usage + * reference in ax88772_bind() (pm_runtime_get_noresume()) and + * dropping it in unbind(), which effectively blocks autosuspend. + */ .supports_autosuspend = 1, .disable_hub_initiated_lpm = 1, };