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 D3B5730BB9A; Mon, 13 Oct 2025 15:18:37 +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=1760368717; cv=none; b=GULdmb6bwOXgdOLIp86xL6l1VkhAitiwDbpU5+Vkv1UFTpUEyBgheXnaYgIW3qpEdqc/l3s7Nbai5LrE2/3b8PHKMSayvnQcNIw2/Vh4hotAvAZQ04s24n9JtL1LYrpUNxsW6qPR+l8M2/HweVM+Cs1UJ++R5OMaKh4ooVmPFPc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760368717; c=relaxed/simple; bh=o5QrofD7a4BRKwEs5cTvr58q3lL9xvw6uV0B3xrp6sA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ANpmda1Z/AsY2gzQZamd2jMxMJ4uf1wnsDCMRLSat59WQT2sGZtH4agcq2PO+BuzPftHruFXgBCF1LsbFAfyfHxsyGiNGBGPftoB5hcjlhpOaKbYWiQe0uO4kzPcxNQG2xuEyT01G66u5XPEmPWkwFoBirl5n1aQZ+MKgjbBIjc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zOE+x//u; 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="zOE+x//u" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5AF21C4CEE7; Mon, 13 Oct 2025 15:18:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1760368717; bh=o5QrofD7a4BRKwEs5cTvr58q3lL9xvw6uV0B3xrp6sA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zOE+x//u7clitvTn1U2qzJ4H/9/GcXX4farxAi8z7d+7hQTeyhr0J3OVQ25XwgU/1 VMUOSnA3lJNNjkYd9O+lEx9S2iM2K/eLu3a1j5dkdIkjqxJgbUBme547DmOKlMvC3t HK/d/0f9d9nRgNHII3/zOmEdXIyDIDAeOv7i6FYs= 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 6.12 259/262] net: usb: asix: hold PM usage ref to avoid PM/MDIO + RTNL deadlock Date: Mon, 13 Oct 2025 16:46:41 +0200 Message-ID: <20251013144335.560742997@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251013144326.116493600@linuxfoundation.org> References: <20251013144326.116493600@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 6.12-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); @@ -919,6 +934,13 @@ 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: @@ -948,6 +970,8 @@ 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) @@ -1600,6 +1624,11 @@ 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, };