From patchwork Tue Jan 16 12:43:50 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fabrice Gasnier X-Patchwork-Id: 10166789 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 263BF601E7 for ; Tue, 16 Jan 2018 12:48:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1749C2847B for ; Tue, 16 Jan 2018 12:48:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0C00B28520; Tue, 16 Jan 2018 12:48:41 +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=-4.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_MED autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 204722847B for ; Tue, 16 Jan 2018 12:48:40 +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=vE59FakZFzcUixGgnB0zFqoQcQH6WmvLXpCViB+1bXk=; b=njB4Gu+8ALRge4 YtZXSbTT4r841f1FsS6++Iu3yT2a2vGIC7ax0os7EYaHuwpA5fVakgIg1czQi5ltr8Livx4Q7Ywg0 bfCkSzJcEQRjvdClS3kiPwZ4WsOGk66I56xuL2ZbaTGyGeGI04vDwAr2/4w9ZlTRgqPRwN+6Y3ShU 3tX4SXxqIuYuSvh8DxW+PJ4/sQqCTakrge8DXmdy1+v2GtLnAIYLfN73RP2RotWJhgq5mgtHkqR0X seOnMdsEuc7wSJdNmuGDippPU4X+AA0WCtPTX+fwcNH4wjZQR9nTHGAIVcZHOABgGz0eP0341/iUr 1JjBpgMaMWQUL+5UW/Aw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.89 #1 (Red Hat Linux)) id 1ebQfL-0001TI-P1; Tue, 16 Jan 2018 12:48:35 +0000 Received: from mx08-00178001.pphosted.com ([91.207.212.93] helo=mx07-00178001.pphosted.com) by bombadil.infradead.org with esmtps (Exim 4.89 #1 (Red Hat Linux)) id 1ebQc9-0005nA-MR for linux-arm-kernel@lists.infradead.org; Tue, 16 Jan 2018 12:45:21 +0000 Received: from pps.filterd (m0046661.ppops.net [127.0.0.1]) by mx08-.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id w0GChpf6009052; Tue, 16 Jan 2018 13:44:45 +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 2fgyb75rd8-1 (version=TLSv1 cipher=ECDHE-RSA-AES256-SHA bits=256 verify=NOT); Tue, 16 Jan 2018 13:44:45 +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 D0A9A34; Tue, 16 Jan 2018 12:44:44 +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 B2AAA26EF; Tue, 16 Jan 2018 12:44:44 +0000 (GMT) Received: from localhost (10.75.127.49) by SFHDAG5NODE3.st.com (10.75.127.15) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Tue, 16 Jan 2018 13:44:44 +0100 From: Fabrice Gasnier To: , , , , Subject: [PATCH 7/8] pwm: stm32: use input prescaler to improve period capture Date: Tue, 16 Jan 2018 13:43:50 +0100 Message-ID: <1516106631-18722-8-git-send-email-fabrice.gasnier@st.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1516106631-18722-1-git-send-email-fabrice.gasnier@st.com> References: <1516106631-18722-1-git-send-email-fabrice.gasnier@st.com> MIME-Version: 1.0 X-Originating-IP: [10.75.127.49] X-ClientProxiedBy: SFHDAG4NODE3.st.com (10.75.127.12) To SFHDAG5NODE3.st.com (10.75.127.15) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2018-01-16_05:, , signatures=0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20180116_044518_039217_DBDAB9BD X-CRM114-Status: GOOD ( 13.03 ) 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: mark.rutland@arm.com, devicetree@vger.kernel.org, benjamin.gaignard@st.com, linux-pwm@vger.kernel.org, linux@armlinux.org.uk, linux-kernel@vger.kernel.org, mcoquelin.stm32@gmail.com, fabrice.gasnier@st.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 Using input prescaler, capture unit will trigger DMA once every configurable /2, /4 or /8 events (rising edge). This can help improve period (only) capture accuracy. Signed-off-by: Fabrice Gasnier --- drivers/pwm/pwm-stm32.c | 67 ++++++++++++++++++++++++++++++++++++++-- include/linux/mfd/stm32-timers.h | 1 + 2 files changed, 66 insertions(+), 2 deletions(-) diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c index c890404..6b99d92 100644 --- a/drivers/pwm/pwm-stm32.c +++ b/drivers/pwm/pwm-stm32.c @@ -9,6 +9,7 @@ * pwm-atmel.c from Bo Shen */ +#include #include #include #include @@ -257,7 +258,7 @@ static int stm32_pwm_capture(struct pwm_chip *chip, struct pwm_device *pwm, struct stm32_pwm *priv = to_stm32_pwm_dev(chip); unsigned long long prd, div, dty; unsigned long rate; - unsigned int psc = 0, scale; + unsigned int psc = 0, icpsc, scale; u32 raw_prd, raw_dty; int ret = 0; @@ -314,6 +315,7 @@ static int stm32_pwm_capture(struct pwm_chip *chip, struct pwm_device *pwm, /* * Got a capture. Try to improve accuracy at high rates: * - decrease counter clock prescaler, scale up to max rate. + * - use input prescaler, capture once every /2 /4 or /8 edges. */ if (raw_prd) { u32 max_arr = priv->max_arr - 0x1000; /* arbitrary margin */ @@ -335,8 +337,69 @@ static int stm32_pwm_capture(struct pwm_chip *chip, struct pwm_device *pwm, raw_dty = priv->capture[1]; } + /* Compute intermediate period not to exceed timeout at low rates */ prd = (unsigned long long)raw_prd * (psc + 1) * NSEC_PER_SEC; - result->period = DIV_ROUND_UP_ULL(prd, rate); + do_div(prd, rate); + + for (icpsc = 0; icpsc < MAX_TIM_ICPSC ; icpsc++) { + /* input prescaler: also keep arbitrary margin */ + if (raw_prd >= (priv->max_arr - 0x1000) >> (icpsc + 1)) + break; + if (prd >= (tmo_ms * NSEC_PER_MSEC) >> (icpsc + 2)) + break; + } + + if (!icpsc) + goto done; + + /* Last chance to improve period accuracy, using input prescaler */ + regmap_update_bits(priv->regmap, + pwm->hwpwm < 2 ? TIM_CCMR1 : TIM_CCMR2, + TIM_CCMR_IC1PSC | TIM_CCMR_IC2PSC, + FIELD_PREP(TIM_CCMR_IC1PSC, icpsc) | + FIELD_PREP(TIM_CCMR_IC2PSC, icpsc)); + + ret = stm32_pwm_do_capture(priv, pwm, tmo_ms); + if (ret) + goto stop; + + raw_prd = priv->capture[0]; + raw_dty = priv->capture[1]; + + if (raw_dty >= (raw_prd >> icpsc)) { + /* + * We may fall here using input prescaler, when input + * capture starts on high side (before falling edge). + * Example with icpsc to capture on each 4 events: + * + * start 1st capture 2nd capture + * v v v + * ___ _____ _____ _____ _____ ____ + * TI1..4 |__| |__| |__| |__| |__| + * v v . . . . . v v + * icpsc1/3: . 0 . 1 . 2 . 3 . 0 + * icpsc2/4: 0 1 2 3 0 + * v v v v + * CCR1/3 ......t0..............................t2 + * CCR2/4 ..t1..............................t1'... + * . . . + * Capture0: .<----------------------------->. + * Capture1: .<-------------------------->. . + * . . . + * Period: .<------> . . + * Low side: .<>. + * + * Result: + * - Period = (t2 - t0) / icpsc + * - Duty = Period - Low side = Period - (Capture0 - Capture1) + */ + raw_dty = priv->capture[0] - priv->capture[1]; + raw_dty = (raw_prd >> icpsc) - raw_dty; + } + +done: + prd = (unsigned long long)raw_prd * (psc + 1) * NSEC_PER_SEC; + result->period = DIV_ROUND_UP_ULL(prd, rate << icpsc); dty = (unsigned long long)raw_dty * (psc + 1) * NSEC_PER_SEC; result->duty_cycle = DIV_ROUND_UP_ULL(dty, rate); stop: diff --git a/include/linux/mfd/stm32-timers.h b/include/linux/mfd/stm32-timers.h index 219eccc..b67cb28 100644 --- a/include/linux/mfd/stm32-timers.h +++ b/include/linux/mfd/stm32-timers.h @@ -77,6 +77,7 @@ #define TIM_BDTR_BK2P BIT(25) /* Break 2 input polarity */ #define MAX_TIM_PSC 0xFFFF +#define MAX_TIM_ICPSC 0x3 #define TIM_CR2_MMS_SHIFT 4 #define TIM_CR2_MMS2_SHIFT 20 #define TIM_SMCR_TS_SHIFT 4