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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 8B818C7618F for ; Mon, 22 Jul 2019 22:05:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F1E021955 for ; Mon, 22 Jul 2019 22:05:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563833117; bh=6wCqVFLfAE5EJfHAjcadIprMjvR25gD3bmKgqCjUMOE=; h=In-Reply-To:References:Subject:To:Cc:From:Date:List-ID:From; b=w7ozPVtPiBz6US6LiAuIvX3uKOu/j07vbdHB59UG4F5e+xxaauYVQu2cmkicjbSrl dRbXyg0k+c0xMdpQNdK5+oEYddfTD4VrSrEVdd1Li1QqulZ1am0LfEpLkLTLOd/3+H BxNZz39UAD3S6YbAo61H/BdPwrSgvAlqVxnP3j+4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732987AbfGVWFQ (ORCPT ); Mon, 22 Jul 2019 18:05:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:52266 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727170AbfGVWFP (ORCPT ); Mon, 22 Jul 2019 18:05:15 -0400 Received: from kernel.org (unknown [104.132.0.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C53FE21951; Mon, 22 Jul 2019 22:05:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563833114; bh=6wCqVFLfAE5EJfHAjcadIprMjvR25gD3bmKgqCjUMOE=; h=In-Reply-To:References:Subject:To:Cc:From:Date:From; b=CfO6y/van+mSGWSA1XbY6Gu0BXxfvN5weJjudshmWAPFMBcjyeDEfoDeRUQDY3D/z qR3GIpxO0+H87UMITd3txerCPUlZuLa/VT+ODujO7vaZ4Ng+/ft7sV5ZfreEE3lPJE 2TPM3yNcT3yGlvGVuP8mrWFmocFgvriXO1gKdgJ4= Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable In-Reply-To: <20190711130359.1060-1-geert+renesas@glider.be> References: <20190711130359.1060-1-geert+renesas@glider.be> Subject: Re: [PATCH] clk: renesas: cpg-mssr: Fix reset control race condition To: Geert Uytterhoeven , Michael Turquette Cc: Yao Lihua , Yoshihiro Shimoda , Wolfram Sang , linux-clk@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven From: Stephen Boyd User-Agent: alot/0.8.1 Date: Mon, 22 Jul 2019 15:05:13 -0700 Message-Id: <20190722220514.C53FE21951@mail.kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Geert Uytterhoeven (2019-07-11 06:03:59) > The module reset code in the Renesas CPG/MSSR driver uses > read-modify-write (RMW) operations to write to a Software Reset Register > (SRCRn), and simple writes to write to a Software Reset Clearing > Register (SRSTCLRn), as was mandated by the R-Car Gen2 and Gen3 Hardware > User's Manuals. >=20 > However, this may cause a race condition when two devices are reset in > parallel: if the reset for device A completes in the middle of the RMW > operation for device B, device A may be reset again, causing subtle > failures (e.g. i2c timeouts): >=20 > thread A thread B > -------- -------- Applied to clk-fixes