From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8146AC43218 for ; Fri, 26 Apr 2019 10:47:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4962920693 for ; Fri, 26 Apr 2019 10:47:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="mYQUEDun" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726173AbfDZKrS (ORCPT ); Fri, 26 Apr 2019 06:47:18 -0400 Received: from mail-lf1-f67.google.com ([209.85.167.67]:33613 "EHLO mail-lf1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725944AbfDZKrR (ORCPT ); Fri, 26 Apr 2019 06:47:17 -0400 Received: by mail-lf1-f67.google.com with SMTP id j11so2160491lfm.0; Fri, 26 Apr 2019 03:47:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=S9WmBj7lYS3B9JO11dPKodyj6vLzXViJHTZDgC2h0T8=; b=mYQUEDun/9QyUHJmOREcbNmw3b5fNI2u65bIzrZMlPq22QmuL24jsLtzZ7k46L+Eh9 A0Ei+jiYHd3jgBWuURFXtl9rJYGmxRbFkr5ABF+CZ2NKHI+X4H2ZlzoPHQIuj0BgaDNK e8jdpaVP5lBNHivdvX5U13BChJzvZHn5v8sxixBM/86fU2nScwKIski5Cg98VBiEUYaT FoxqjH3sHixBrpWJSFG8ZsQSVFBoj+bkZ+C8/bi7a56KtWW7kGQ2eDUpX0tvbI47JFxg p0imXFOU2wQyWUdgwHJSsxyYMib5GsKoq4bd8U6X9k+NkksE+NHCol2InZH/nVtQo7fS yIMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=S9WmBj7lYS3B9JO11dPKodyj6vLzXViJHTZDgC2h0T8=; b=Wced/0FIc5zfvR4g2WqdStLo63uhfDRYD8TeDLeULNcxt9ToFclBzcntkA3aaHq4DQ EmaZyCClBr11XSM29GXz8Fiu7gyVDias0GSAAgtKdlbSIHiet2oCr3WimP777bbf0oPh OPZcEl6Z+GX/vM/BbXlCUFNY//qJBbuWdTQjqB89ocj1EqW803jXwEgtR7qTJWLDodSu A+8RLc+QWXCmkGz1ti1KmwuxXL2xkdBeX5U/hkpJ4ORvKjPB4rqmhsvMxpEvAXOBxqH6 O04piLzBX5QGbOc99yptySWHUcSKQpyieSvU/QIIk+r+aLmh/9OQAJmLMoyBQHJfQS1e vCXw== X-Gm-Message-State: APjAAAXVYhqtk/w2Pyj47knrXHPYHu9T4QJvfx60i3gkDzDCoZtBAxvu MEdn6jv9bsyuiqhk+ZXgF9k= X-Google-Smtp-Source: APXvYqwkbpmvQPjj5HIpaDDvrc5bAqcingJoTDlqH73duzuzxHQKS+3BtgTR5BD+WM94vYTL6KRj6w== X-Received: by 2002:a19:7d04:: with SMTP id y4mr6435872lfc.153.1556275634600; Fri, 26 Apr 2019 03:47:14 -0700 (PDT) Received: from localhost.localdomain ([5.164.240.123]) by smtp.gmail.com with ESMTPSA id 10sm1801799ljc.48.2019.04.26.03.47.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Apr 2019 03:47:13 -0700 (PDT) From: Serge Semin To: Richard Leitner , Greg Kroah-Hartman Cc: Serge Semin , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] usb: usb251xb: Lock i2c-bus segment the hub resides Date: Fri, 26 Apr 2019 13:46:50 +0300 Message-Id: <20190426104650.30240-1-fancer.lancer@gmail.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190424144914.10580-1-fancer.lancer@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org SMBus slave configuration is activated by CFG_SEL[1:0]=0x1 pins state. This is the mode the hub is supposed to be to let this driver work correctly. But a race condition might happen right after reset is cleared due to CFG_SEL[0] pin being multiplexed with SMBus SCL function. In case if the reset pin is handled by a i2c GPIO expander, which is also placed at the same i2c-bus segment as the usb251x SMB-interface connected to, then the hub reset clearance might cause the CFG_SEL[0] being latched in unpredictable state. So sometimes the hub configuration mode might be 0x1 (as expected), but sometimes being 0x0, which doesn't imply to have the hub SMBus-slave interface activated and consequently causes this driver failure. In order to fix the problem we must make sure the GPIO-reset chip doesn't reside the same i2c-bus segment as the SMBus-interface of the hub. If it doesn't, we can safely block the segment for the time the reset is cleared to prevent anyone generating a traffic at the i2c-bus SCL lane connected to the CFG_SEL[0] pin. But if it does, nothing we can do, so just return an error. If we locked the i2c-bus segment and tried to communicate with the GPIO-expander, it would cause a deadlock. If we didn't lock the i2c-bus segment, it would randomly cause the CFG_SEL[0] bit flip. Signed-off-by: Serge Semin Signed-off-by: Greg Kroah-Hartman --- Changelog v2 - Execute the check code only if GPIOLIB is enabled (reported by a build robot). --- drivers/usb/misc/usb251xb.c | 62 +++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) diff --git a/drivers/usb/misc/usb251xb.c b/drivers/usb/misc/usb251xb.c index 04684849d683..cdc80e8c2d8a 100644 --- a/drivers/usb/misc/usb251xb.c +++ b/drivers/usb/misc/usb251xb.c @@ -12,6 +12,7 @@ #include #include +#include #include #include #include @@ -222,11 +223,51 @@ static const struct usb251xb_data usb2517i_data = { .product_str = "USB2517i", }; +#ifdef CONFIG_GPIOLIB +static int usb251xb_check_dev_children(struct device *dev, void *child) +{ + if (dev->type == &i2c_adapter_type) { + return device_for_each_child(dev, child, + usb251xb_check_dev_children); + } + + return (dev == child); +} + +static int usb251x_check_gpio_chip(struct usb251xb *hub) +{ + struct gpio_chip *gc = gpiod_to_chip(hub->gpio_reset); + struct i2c_adapter *adap = hub->i2c->adapter; + int ret; + + if (!hub->gpio_reset) + return 0; + + if (!gc) + return -EINVAL; + + ret = usb251xb_check_dev_children(&adap->dev, gc->parent); + if (ret) { + dev_err(hub->dev, "Reset GPIO chip is at the same i2c-bus\n"); + return -EINVAL; + } + + return 0; +} +#else +static int usb251x_check_gpio_chip(struct usb251xb *hub) +{ + return 0; +} +#endif + static void usb251xb_reset(struct usb251xb *hub, int state) { if (!hub->gpio_reset) return; + i2c_lock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT); + gpiod_set_value_cansleep(hub->gpio_reset, state); /* wait for hub recovery/stabilization */ @@ -234,6 +275,8 @@ static void usb251xb_reset(struct usb251xb *hub, int state) usleep_range(500, 750); /* >=500us at power on */ else usleep_range(1, 10); /* >=1us at power down */ + + i2c_unlock_bus(hub->i2c->adapter, I2C_LOCK_SEGMENT); } static int usb251xb_connect(struct usb251xb *hub) @@ -621,6 +664,25 @@ static int usb251xb_probe(struct usb251xb *hub) } } + /* + * usb251x SMBus-slave SCL lane is muxed with CFG_SEL0 pin. So if anyone + * tries to work with the bus at the moment the hub reset is released, + * it may cause an invalid config being latched by usb251x. Particularly + * one of the config modes makes the hub loading a default registers + * value without SMBus-slave interface activation. If the hub + * accidentally gets this mode, this will cause the driver SMBus- + * functions failure. Normally we could just lock the SMBus-segment the + * hub i2c-interface resides for the device-specific reset timing. But + * the GPIO controller, which is used to handle the hub reset, might be + * placed at the same i2c-bus segment. In this case an error should be + * returned since we can't safely use the GPIO controller to clear the + * reset state (it may affect the hub configuration) and we can't lock + * the i2c-bus segment (it will cause a deadlock). + */ + err = usb251x_check_gpio_chip(hub); + if (err) + return err; + err = usb251xb_connect(hub); if (err) { dev_err(dev, "Failed to connect hub (%d)\n", err); -- 2.21.0