From patchwork Wed Dec 23 17:21:51 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wolfram Sang X-Patchwork-Id: 352113 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=-16.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, 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 53309C433E0 for ; Wed, 23 Dec 2020 17:22:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0CE662220B for ; Wed, 23 Dec 2020 17:22:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726384AbgLWRWn (ORCPT ); Wed, 23 Dec 2020 12:22:43 -0500 Received: from www.zeus03.de ([194.117.254.33]:41284 "EHLO mail.zeus03.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726047AbgLWRWn (ORCPT ); Wed, 23 Dec 2020 12:22:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=simple; d=sang-engineering.com; h= from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; s=k1; bh=7G4VEydHXtCuh4 d5tp3VbNjaXPr7rBC2TMVcx8Y/rhA=; b=jPPAaF+kVX3SWT6dOm+DcEZFJ06aL4 pojaRFwYY9qESsCkLO2FgvFt/iV5I80o2Glzg3yI3gZbOWOIPLxQGgZ7zgz5C4Xl LMh3AzW9Vz6NE6FYJEcOndGmFdNuigXE0k9aa6Iw47ukKc6wFnLNM7wRSVH1juWW Zs8FXgf5MQcTM= Received: (qmail 543566 invoked from network); 23 Dec 2020 18:22:01 +0100 Received: by mail.zeus03.de with ESMTPSA (TLS_AES_256_GCM_SHA384 encrypted, authenticated); 23 Dec 2020 18:22:01 +0100 X-UD-Smtp-Session: l3s3148p1@//Hb7SS3tudUhszw From: Wolfram Sang To: linux-i2c@vger.kernel.org Cc: linux-renesas-soc@vger.kernel.org, Kuninori Morimoto , Yoshihiro Shimoda , Wolfram Sang Subject: [PATCH 1/4] i2c: rcar: faster irq code to minimize HW race condition Date: Wed, 23 Dec 2020 18:21:51 +0100 Message-Id: <20201223172154.34462-2-wsa+renesas@sang-engineering.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201223172154.34462-1-wsa+renesas@sang-engineering.com> References: <20201223172154.34462-1-wsa+renesas@sang-engineering.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org 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 --- 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 217def2d7cb4..824586d7ee56 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -91,7 +91,6 @@ #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) @@ -621,7 +620,7 @@ 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 @@ -630,13 +629,11 @@ 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);