From patchwork Thu Mar 21 16:47:22 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fabrice Gasnier X-Patchwork-Id: 10864043 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 B17C013B5 for ; Thu, 21 Mar 2019 16:48:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8F53E1FF73 for ; Thu, 21 Mar 2019 16:48:09 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 82A5228BAA; Thu, 21 Mar 2019 16:48:09 +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 9D9322A1AD for ; Thu, 21 Mar 2019 16:48:07 +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:References:In-Reply-To: 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: List-Owner; bh=BStCNUy3OapHwBPd0aMl4ball7uLsUa242d5Ju7KCzA=; b=R9w3ViUeC4ZBkX mnt6cL7gNqFX8UbIFRncRqHFgYFglx81wPcb72oaPmjdc4Frbt/qorPxZPvbg05YN7cYyVRjduiFX w0PUCNuYGdNlgOXcxyZY7nvfjcyDjCUCZj9AtyzsSP/6c4y3rnXhPYReKVEzDp1J06PM54XtGmV/f pvXW0Dfandt8ve+E15f6va2rbJo7dRRoGdvsfhg/ifA0cCTvLIzVrHZCCvD8NeKu9JvD0UC+0lhcL jWMa9JY3Id3RcglZqxl1f2mrQ7mDhEU2W+w8v4NAC0r7jiWISKAZC0hfz9uNcv93HyBKYclDp1Kqe QEBAM2ZihhwrWm6C7eFg==; 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 1h70rK-0000ZL-Oz; Thu, 21 Mar 2019 16:48:02 +0000 Received: from mx08-00178001.pphosted.com ([91.207.212.93] helo=mx07-00178001.pphosted.com) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1h70r1-0000ES-V3 for linux-arm-kernel@lists.infradead.org; Thu, 21 Mar 2019 16:47:47 +0000 Received: from pps.filterd (m0046661.ppops.net [127.0.0.1]) by mx08-00178001.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x2LGkp20007997; Thu, 21 Mar 2019 17:47:37 +0100 Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx08-00178001.pphosted.com with ESMTP id 2r8rwkek1h-1 (version=TLSv1 cipher=ECDHE-RSA-AES256-SHA bits=256 verify=NOT); Thu, 21 Mar 2019 17:47:37 +0100 Received: from zeta.dmz-eu.st.com (zeta.dmz-eu.st.com [164.129.230.9]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id CBBC734; Thu, 21 Mar 2019 16:47:36 +0000 (GMT) Received: from Webmail-eu.st.com (sfhdag5node3.st.com [10.75.127.15]) by zeta.dmz-eu.st.com (STMicroelectronics) with ESMTP id A1FC75670; Thu, 21 Mar 2019 16:47:36 +0000 (GMT) Received: from localhost (10.75.127.45) by SFHDAG5NODE3.st.com (10.75.127.15) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Thu, 21 Mar 2019 17:47:36 +0100 From: Fabrice Gasnier To: Subject: [PATCH v2 1/8] iio: adc: stm32-dfsdm: make spi_master_freq more accurate Date: Thu, 21 Mar 2019 17:47:22 +0100 Message-ID: <1553186849-6261-2-git-send-email-fabrice.gasnier@st.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1553186849-6261-1-git-send-email-fabrice.gasnier@st.com> References: <1553186849-6261-1-git-send-email-fabrice.gasnier@st.com> MIME-Version: 1.0 X-Originating-IP: [10.75.127.45] X-ClientProxiedBy: SFHDAG7NODE3.st.com (10.75.127.21) To SFHDAG5NODE3.st.com (10.75.127.15) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-03-21_07:, , signatures=0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190321_094744_290395_20E1D035 X-CRM114-Status: GOOD ( 13.06 ) 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: lars@metafoo.de, olivier.moysan@st.com, alexandre.torgue@st.com, linux-iio@vger.kernel.org, pmeerw@pmeerw.net, arnaud.pouliquen@st.com, linux-kernel@vger.kernel.org, mcoquelin.stm32@gmail.com, knaack.h@gmx.de, fabrice.gasnier@st.com, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.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 Current ckout divider may be set to a value that makes ckout to exceed spi-max-frequency. Rather use lower value (e.g. round up divider when ckout isn't accurate). Also when the SPI clock isn't accurate, 'spi_master_freq' is filled in with expected frequency. Use computed value instead to be more accurate: - e.g. source clock / (CKOUTDIV + 1) Enforce checks on the divider: ckoutdiv range can be from 1-255 to provide divider of 2-256. Signed-off-by: Fabrice Gasnier --- Changes in v2: - rework the way to determine ckoutdiv bitfield: deal with divider directly to explicitly handle the rounding, the range constraints of 2-256 and the divider = ckoutdiv + 1. --- drivers/iio/adc/stm32-dfsdm-core.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/iio/adc/stm32-dfsdm-core.c b/drivers/iio/adc/stm32-dfsdm-core.c index bf089f5..472b809 100644 --- a/drivers/iio/adc/stm32-dfsdm-core.c +++ b/drivers/iio/adc/stm32-dfsdm-core.c @@ -199,7 +199,7 @@ static int stm32_dfsdm_parse_of(struct platform_device *pdev, { struct device_node *node = pdev->dev.of_node; struct resource *res; - unsigned long clk_freq; + unsigned long clk_freq, divider; unsigned int spi_freq, rem; int ret; @@ -243,13 +243,20 @@ static int stm32_dfsdm_parse_of(struct platform_device *pdev, return 0; } - priv->spi_clk_out_div = div_u64_rem(clk_freq, spi_freq, &rem) - 1; - if (!priv->spi_clk_out_div) { - /* spi_clk_out_div == 0 means ckout is OFF */ + divider = div_u64_rem(clk_freq, spi_freq, &rem); + /* Round up divider when ckout isn't precise, not to exceed spi_freq */ + if (rem) + divider++; + + /* programmable divider is in range of [2:256] */ + if (divider < 2 || divider > 256) { dev_err(&pdev->dev, "spi-max-frequency not achievable\n"); return -EINVAL; } - priv->dfsdm.spi_master_freq = spi_freq; + + /* SPI clock output divider is: divider = CKOUTDIV + 1 */ + priv->spi_clk_out_div = divider - 1; + priv->dfsdm.spi_master_freq = clk_freq / (priv->spi_clk_out_div + 1); if (rem) { dev_warn(&pdev->dev, "SPI clock not accurate\n");