From patchwork Wed Apr 24 14:49:14 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 10914973 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 979E2161F for ; Wed, 24 Apr 2019 14:49:58 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8605328720 for ; Wed, 24 Apr 2019 14:49:58 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7A30A287C0; Wed, 24 Apr 2019 14:49:58 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 041F428720 for ; Wed, 24 Apr 2019 14:49:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732306AbfDXOtu (ORCPT ); Wed, 24 Apr 2019 10:49:50 -0400 Received: from mail-lj1-f196.google.com ([209.85.208.196]:35766 "EHLO mail-lj1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731011AbfDXOtr (ORCPT ); Wed, 24 Apr 2019 10:49:47 -0400 Received: by mail-lj1-f196.google.com with SMTP id t4so17161711ljc.2; Wed, 24 Apr 2019 07:49:44 -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:mime-version :content-transfer-encoding; bh=bofPGkO0Fr+MuENc58WU9P5S59OCZQC8382116tFtCg=; b=c50nKEv/w+xO5RPKV7gxufTcXqfQ+1tT10gGQtegZOKIa6aYKeVzOCnewV2HGwleI9 eVE4PXuaAC73S3WlUUKk0GRSZRReJsQ3DU04GmzMn0xA24D0Xp4hgYII5bj2q/7pFnhc nBo6Co17Tf+YoOZY4QcbOtZBJOkrpNOCAz6wMZCRK6TSIWpqxEYJrmS695Gagup0cxSc uKDFBu/cDNiKsBK4XFWeC9OIDx4meVYOKLD6YuBN5ncAHPb8LPFTmDDpwQZxdT2+tm5J fFdCyQnxRhKLWDJBLjICNzTlIMWGpn3kzOXwXmXvprzl3DSvzpXCxf5BQVFzUTImfWNz ytAw== 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:mime-version :content-transfer-encoding; bh=bofPGkO0Fr+MuENc58WU9P5S59OCZQC8382116tFtCg=; b=E4PTwP6JAxqm23LuPLsJtLfwNKA27vqEsCvyZIBIpO15aFkGc9D2o3vRh9phqAvAdJ 0c4DtEA2TpKdZJz9uxWIrpWKh2fCQpiElzYFb2Io29lKu8T33N8esyWIuBGV/4rRyd7N w+0b3iFOa32vQnZAdkUT/pj/X/VCl+v0aSnaPTSjug1hU+nn2Foxy9AjNYHrpr8qBx9G /A4++AdQ1Mo4UXFn34no0PblKtWiiolyQtndYr3QtmXO7vktd+c9VMwC4B9AdFEltY+2 ACUx5eMDGTcikCaoZylP7AJ71xSkly692tyDZPTvwqPs2hhMVLBNFSVubEQK+j/SWDWT o95w== X-Gm-Message-State: APjAAAUYYVu9XqRwlXjTwzf0aYpitfg2ao4TyiKEqLEYBUlEul6byYAR nstz83Lz0jdNBW2JMuhBiJj/QlViKec= X-Google-Smtp-Source: APXvYqyoXVZbgnCl1EFhYDQDLYZOELvk49LAXkjFsQlYlRe/vxojRIrDSRrx9IbwM0rTmBV8UcM7ug== X-Received: by 2002:a2e:4e12:: with SMTP id c18mr17951314ljb.3.1556117383924; Wed, 24 Apr 2019 07:49:43 -0700 (PDT) Received: from localhost.localdomain ([5.164.240.123]) by smtp.gmail.com with ESMTPSA id h26sm2273109lfm.11.2019.04.24.07.49.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Apr 2019 07:49:42 -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] usb: usb251xb: Lock i2c-bus segment the hub resides Date: Wed, 24 Apr 2019 17:49:14 +0300 Message-Id: <20190424144914.10580-1-fancer.lancer@gmail.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 --- drivers/usb/misc/usb251xb.c | 55 +++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) diff --git a/drivers/usb/misc/usb251xb.c b/drivers/usb/misc/usb251xb.c index 04684849d683..939b3bedd4c8 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 +223,44 @@ static const struct usb251xb_data usb2517i_data = { .product_str = "USB2517i", }; +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; +} + 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 +268,8 @@ 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 +657,25 @@ 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);