From patchwork Mon Mar 15 13:54:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 401313 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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, 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 9C037C433DB for ; Mon, 15 Mar 2021 14:05:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 77F9764DAD for ; Mon, 15 Mar 2021 14:05:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234731AbhCOOE6 (ORCPT ); Mon, 15 Mar 2021 10:04:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:36788 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232151AbhCON6n (ORCPT ); Mon, 15 Mar 2021 09:58:43 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0064264F38; Mon, 15 Mar 2021 13:58:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1615816713; bh=f+o1AMYCHacmqHLrAENwRc2ZmliogSAderchS9BeCKo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=u4eTLcgFSFnYmjM5CVZWNciS60xEGRgaU8UkPflysJ57rcOm4QeNsvjLx6gTz/WwD +MzZ1f0yk4AVVw6mzg8YIygva6VNCuzpq5IIkTaywHz33oraudb8ZKnb+5vQBDou5F PdH0g/1he/GfW+7L/gGymutlkb3LGMH1vvgPsIgs= From: gregkh@linuxfoundation.org To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Wolfram Sang , =?utf-8?q?Niklas_S?= =?utf-8?b?w7ZkZXJsdW5k?= , Wolfram Sang , Sasha Levin Subject: [PATCH 5.4 062/168] i2c: rcar: faster irq code to minimize HW race condition Date: Mon, 15 Mar 2021 14:54:54 +0100 Message-Id: <20210315135552.408449230@linuxfoundation.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210315135550.333963635@linuxfoundation.org> References: <20210315135550.333963635@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Greg Kroah-Hartman From: Wolfram Sang [ Upstream commit c7b514ec979e23a08c411f3d8ed39c7922751422 ] To avoid the HW race condition on R-Car Gen2 and earlier, we need to write to ICMCR as soon as possible in the interrupt handler. We can improve this by writing a static value instead of masking out bits. Signed-off-by: Wolfram Sang Reviewed-by: Niklas Söderlund Signed-off-by: Wolfram Sang Signed-off-by: Sasha Levin --- drivers/i2c/busses/i2c-rcar.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c index 9c162a01a584..9d54ae935524 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -89,7 +89,6 @@ #define RCAR_BUS_PHASE_START (MDBS | MIE | ESG) #define RCAR_BUS_PHASE_DATA (MDBS | MIE) -#define RCAR_BUS_MASK_DATA (~(ESG | FSB) & 0xFF) #define RCAR_BUS_PHASE_STOP (MDBS | MIE | FSB) #define RCAR_IRQ_SEND (MNR | MAL | MST | MAT | MDE) @@ -616,7 +615,7 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv) /* * This driver has a lock-free design because there are IP cores (at least * R-Car Gen2) which have an inherent race condition in their hardware design. - * There, we need to clear RCAR_BUS_MASK_DATA bits as soon as possible after + * There, we need to switch to RCAR_BUS_PHASE_DATA as soon as possible after * the interrupt was generated, otherwise an unwanted repeated message gets * generated. It turned out that taking a spinlock at the beginning of the ISR * was already causing repeated messages. Thus, this driver was converted to @@ -625,13 +624,11 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv) static irqreturn_t rcar_i2c_irq(int irq, void *ptr) { struct rcar_i2c_priv *priv = ptr; - u32 msr, val; + u32 msr; /* Clear START or STOP immediately, except for REPSTART after read */ - if (likely(!(priv->flags & ID_P_REP_AFTER_RD))) { - val = rcar_i2c_read(priv, ICMCR); - rcar_i2c_write(priv, ICMCR, val & RCAR_BUS_MASK_DATA); - } + if (likely(!(priv->flags & ID_P_REP_AFTER_RD))) + rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA); msr = rcar_i2c_read(priv, ICMSR);