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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9F64BC77B6E for ; Wed, 12 Apr 2023 08:44:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230398AbjDLIoc (ORCPT ); Wed, 12 Apr 2023 04:44:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230387AbjDLIoQ (ORCPT ); Wed, 12 Apr 2023 04:44:16 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D68E1A4 for ; Wed, 12 Apr 2023 01:43:54 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5F36E630BD for ; Wed, 12 Apr 2023 08:43:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 71337C433EF; Wed, 12 Apr 2023 08:43:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1681289000; bh=sYd6ICRjhfCK/+Zoza1/9PMmL5WhMZ0xzQHAveKZHDw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IBHofUikqR8kA4dIljh4moYIAo7kqH/WvcWEY7hhNmQ3clEC51PKB3vYohZ23klef e8YaTFcZggaiA9j2k0184xiAE89QX0RidUTVLH5M/EP2fvaL5zLIhr9JVCkcdh0oFT ew/veD7fafw3HYs9K5OLrdeGm7x9OuhrPdDmN/7E= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, William Breathitt Gray Subject: [PATCH 6.1 098/164] counter: 104-quad-8: Fix race condition between FLAG and CNTR reads Date: Wed, 12 Apr 2023 10:33:40 +0200 Message-Id: <20230412082840.822017654@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230412082836.695875037@linuxfoundation.org> References: <20230412082836.695875037@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: William Breathitt Gray commit 4aa3b75c74603c3374877d5fd18ad9cc3a9a62ed upstream. The Counter (CNTR) register is 24 bits wide, but we can have an effective 25-bit count value by setting bit 24 to the XOR of the Borrow flag and Carry flag. The flags can be read from the FLAG register, but a race condition exists: the Borrow flag and Carry flag are instantaneous and could change by the time the count value is read from the CNTR register. Since the race condition could result in an incorrect 25-bit count value, remove support for 25-bit count values from this driver; hard-coded maximum count values are replaced by a LS7267_CNTR_MAX define for consistency and clarity. Fixes: 28e5d3bb0325 ("iio: 104-quad-8: Add IIO support for the ACCES 104-QUAD-8") Cc: # 6.1.x Cc: # 6.2.x Link: https://lore.kernel.org/r/20230312231554.134858-1-william.gray@linaro.org/ Signed-off-by: William Breathitt Gray Signed-off-by: Greg Kroah-Hartman --- drivers/counter/104-quad-8.c | 29 ++++++++--------------------- 1 file changed, 8 insertions(+), 21 deletions(-) --- a/drivers/counter/104-quad-8.c +++ b/drivers/counter/104-quad-8.c @@ -97,10 +97,6 @@ struct quad8 { struct quad8_reg __iomem *reg; }; -/* Borrow Toggle flip-flop */ -#define QUAD8_FLAG_BT BIT(0) -/* Carry Toggle flip-flop */ -#define QUAD8_FLAG_CT BIT(1) /* Error flag */ #define QUAD8_FLAG_E BIT(4) /* Up/Down flag */ @@ -133,6 +129,9 @@ struct quad8 { #define QUAD8_CMR_QUADRATURE_X2 0x10 #define QUAD8_CMR_QUADRATURE_X4 0x18 +/* Each Counter is 24 bits wide */ +#define LS7267_CNTR_MAX GENMASK(23, 0) + static int quad8_signal_read(struct counter_device *counter, struct counter_signal *signal, enum counter_signal_level *level) @@ -156,18 +155,10 @@ static int quad8_count_read(struct count { struct quad8 *const priv = counter_priv(counter); struct channel_reg __iomem *const chan = priv->reg->channel + count->id; - unsigned int flags; - unsigned int borrow; - unsigned int carry; unsigned long irqflags; int i; - flags = ioread8(&chan->control); - borrow = flags & QUAD8_FLAG_BT; - carry = !!(flags & QUAD8_FLAG_CT); - - /* Borrow XOR Carry effectively doubles count range */ - *val = (unsigned long)(borrow ^ carry) << 24; + *val = 0; spin_lock_irqsave(&priv->lock, irqflags); @@ -191,8 +182,7 @@ static int quad8_count_write(struct coun unsigned long irqflags; int i; - /* Only 24-bit values are supported */ - if (val > 0xFFFFFF) + if (val > LS7267_CNTR_MAX) return -ERANGE; spin_lock_irqsave(&priv->lock, irqflags); @@ -806,8 +796,7 @@ static int quad8_count_preset_write(stru struct quad8 *const priv = counter_priv(counter); unsigned long irqflags; - /* Only 24-bit values are supported */ - if (preset > 0xFFFFFF) + if (preset > LS7267_CNTR_MAX) return -ERANGE; spin_lock_irqsave(&priv->lock, irqflags); @@ -834,8 +823,7 @@ static int quad8_count_ceiling_read(stru *ceiling = priv->preset[count->id]; break; default: - /* By default 0x1FFFFFF (25 bits unsigned) is maximum count */ - *ceiling = 0x1FFFFFF; + *ceiling = LS7267_CNTR_MAX; break; } @@ -850,8 +838,7 @@ static int quad8_count_ceiling_write(str struct quad8 *const priv = counter_priv(counter); unsigned long irqflags; - /* Only 24-bit values are supported */ - if (ceiling > 0xFFFFFF) + if (ceiling > LS7267_CNTR_MAX) return -ERANGE; spin_lock_irqsave(&priv->lock, irqflags);