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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 D08E8C43381 for ; Wed, 6 Mar 2019 08:56:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A93EF206DD for ; Wed, 6 Mar 2019 08:56:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729588AbfCFI4Y (ORCPT ); Wed, 6 Mar 2019 03:56:24 -0500 Received: from mx07-00178001.pphosted.com ([62.209.51.94]:58413 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729562AbfCFI4W (ORCPT ); Wed, 6 Mar 2019 03:56:22 -0500 Received: from pps.filterd (m0046668.ppops.net [127.0.0.1]) by mx07-00178001.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x268p4eU001192; Wed, 6 Mar 2019 09:55:49 +0100 Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx07-00178001.pphosted.com with ESMTP id 2r0ju8yewp-1 (version=TLSv1 cipher=ECDHE-RSA-AES256-SHA bits=256 verify=NOT); Wed, 06 Mar 2019 09:55:49 +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 585C342; Wed, 6 Mar 2019 08:55:48 +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 0EE9423F7; Wed, 6 Mar 2019 08:55:48 +0000 (GMT) Received: from localhost (10.75.127.46) by SFHDAG5NODE3.st.com (10.75.127.15) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Wed, 6 Mar 2019 09:55:47 +0100 From: Fabrice Gasnier To: CC: , , , , , , , , , , , Subject: [PATCH 1/8] iio: adc: stm32-dfsdm: make spi_master_freq more accurate Date: Wed, 6 Mar 2019 09:55:17 +0100 Message-ID: <1551862524-25098-2-git-send-email-fabrice.gasnier@st.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1551862524-25098-1-git-send-email-fabrice.gasnier@st.com> References: <1551862524-25098-1-git-send-email-fabrice.gasnier@st.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.75.127.46] 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=2019-03-06_06:,, signatures=0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When SPI clock isn't accurate, 'spi_master_freq' is filled in with expected frequency. Use computed value instead: - e.g. source clock / (CKOUTDIV + 1) Also, current divider may be set to value that makes CKOUT to exceed spi-max-frequency. Rather use lower value (e.g. round up divider when ckout isn't accurate). Signed-off-by: Fabrice Gasnier --- drivers/iio/adc/stm32-dfsdm-core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/iio/adc/stm32-dfsdm-core.c b/drivers/iio/adc/stm32-dfsdm-core.c index bf089f5..65b7556 100644 --- a/drivers/iio/adc/stm32-dfsdm-core.c +++ b/drivers/iio/adc/stm32-dfsdm-core.c @@ -243,13 +243,18 @@ 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; + priv->spi_clk_out_div = div_u64_rem(clk_freq, spi_freq, &rem); + + /* round up divider when clkout isn't accurate (e.g. !rem) */ + if (priv->spi_clk_out_div && !rem) + priv->spi_clk_out_div--; + if (!priv->spi_clk_out_div) { /* spi_clk_out_div == 0 means ckout is OFF */ dev_err(&pdev->dev, "spi-max-frequency not achievable\n"); return -EINVAL; } - priv->dfsdm.spi_master_freq = spi_freq; + priv->dfsdm.spi_master_freq = clk_freq / (priv->spi_clk_out_div + 1); if (rem) { dev_warn(&pdev->dev, "SPI clock not accurate\n"); -- 2.7.4