From patchwork Fri Apr 12 07:32:19 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Flavio Suligoi X-Patchwork-Id: 10897377 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 ECE0A14DB for ; Fri, 12 Apr 2019 07:32:47 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C4DFC28AFB for ; Fri, 12 Apr 2019 07:32:47 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B8D1B28E53; Fri, 12 Apr 2019 07:32:47 +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=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 6557928AFB for ; Fri, 12 Apr 2019 07:32:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:Subject:To :From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=pjW6QO7Yl9WGESytKwydHaF6RAyZyvJTz1zJGa4Koio=; b=WrzfFqAaIgBJ1j GaM3tIay4ndXOnyfJDHnSRWSPO5GuCsg65EPit0vPTsCgWoOuHTZAmvVRjfANdBlD8lZaINMvRZ6M nl9LCHzlW4IwENbGiix/mhdpf4NdFwxNjjQl3qIdkDO2SpUOMJ9a0wAskZF6SXDyH+NJceg+GGpV+ doM/9SdE9b/HA2ttxM7+WJzlzDwkdNzcG2oDbY4y4utzSkMtvPdJBp8vRFd4DLn0OPFSJa7vnpAMe sAWuvzcDr7ZKmLwcC2eb6/DBaxAvtEpcg2sWRL37PtS/zKcwYJZXIiZn7iTDf0sZ2c0LzRvCeHUG5 mYFVvydbfz+vYojlig+g==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hEqg1-00044k-GL; Fri, 12 Apr 2019 07:32:45 +0000 Received: from smtp.asem.it ([151.1.184.197]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hEqfw-00043y-E3 for linux-arm-kernel@lists.infradead.org; Fri, 12 Apr 2019 07:32:44 +0000 Received: from webmail.asem.it by asem.it (smtp.asem.it) (SecurityGateway 5.5.0) with ESMTP id SG003809154.MSG for ; Fri, 12 Apr 2019 09:32:34 +0200S Received: from ASAS044.asem.intra (172.16.16.44) by ASAS044.asem.intra (172.16.16.44) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1261.35; Fri, 12 Apr 2019 09:32:33 +0200 Received: from flavio-x.asem.intra (172.16.17.208) by ASAS044.asem.intra (172.16.16.44) with Microsoft SMTP Server id 15.1.1261.35 via Frontend Transport; Fri, 12 Apr 2019 09:32:33 +0200 From: Flavio Suligoi To: Daniel Mack , Haojian Zhuang , Robert Jarzmik , Mark Brown , Jarkko Nikula Subject: [PATCH v2] spi: pxa2xx: fix SCR (divisor) calculation Date: Fri, 12 Apr 2019 09:32:19 +0200 Message-ID: <1555054339-17096-1-git-send-email-f.suligoi@asem.it> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 X-SGHeloLookup-Result: pass smtp.helo=webmail.asem.it (ip=172.16.16.44) X-SGSPF-Result: none (smtp.asem.it) X-SGOP-RefID: str=0001.0A0B0212.5CB03F12.000F, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0 (_st=1 _vt=0 _iwf=0) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190412_003240_656177_EC56D6EA X-CRM114-Status: GOOD ( 12.49 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Flavio Suligoi , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-spi@vger.kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Calculate the divisor for the SCR (Serial Clock Rate), avoiding that the SSP transmission rate can be greater than the device rate. When the division between the SSP clock and the device rate generates a reminder, we have to increment by one the divisor. In this way the resulting SSP clock will never be greater than the device SPI max frequency. For example, with: - ssp_clk = 50 MHz - dev freq = 15 MHz without this patch the SSP clock will be greater than 15 MHz: - 25 MHz for PXA25x_SSP and CE4100_SSP - 16,56 MHz for the others Instead, with this patch, we have in both case an SSP clock of 12.5MHz, so the max rate of the SPI device clock is respected. Signed-off-by: Flavio Suligoi Reviewed-by: Jarkko Nikula Reviewed-by: Jarkko Nikula --- v2: - simplify the code using "DIV_ROUND_UP" v1: - first version drivers/spi/spi-pxa2xx.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c index f7068cc..a35fdcb 100644 --- a/drivers/spi/spi-pxa2xx.c +++ b/drivers/spi/spi-pxa2xx.c @@ -884,10 +884,14 @@ static unsigned int ssp_get_clk_div(struct driver_data *drv_data, int rate) rate = min_t(int, ssp_clk, rate); + /* + * Calculate the divisor for the SCR (Serial Clock Rate), avoiding + * that the SSP transmission rate can be greater than the device rate + */ if (ssp->type == PXA25x_SSP || ssp->type == CE4100_SSP) - return (ssp_clk / (2 * rate) - 1) & 0xff; + return (DIV_ROUND_UP(ssp_clk, 2 * rate) - 1) & 0xff; else - return (ssp_clk / rate - 1) & 0xfff; + return (DIV_ROUND_UP(ssp_clk, rate) - 1) & 0xfff; } static unsigned int pxa2xx_ssp_get_clk_div(struct driver_data *drv_data,