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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 E5C05C6379F for ; Mon, 23 Nov 2020 16:37:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9053C20708 for ; Mon, 23 Nov 2020 16:37:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=pqgruber.com header.i=@pqgruber.com header.b="w2KhMJOr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390132AbgKWQhR (ORCPT ); Mon, 23 Nov 2020 11:37:17 -0500 Received: from mail.pqgruber.com ([52.59.78.55]:41326 "EHLO mail.pqgruber.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729294AbgKWQhQ (ORCPT ); Mon, 23 Nov 2020 11:37:16 -0500 Received: from workstation.tuxnet (213-47-165-233.cable.dynamic.surfer.at [213.47.165.233]) by mail.pqgruber.com (Postfix) with ESMTPSA id C379CC81EEB; Mon, 23 Nov 2020 17:37:13 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pqgruber.com; s=mail; t=1606149434; bh=Kc6Fqrrn44fvOnRrUmkrUS9dVkPwBhPEwVaxBFioCTY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=w2KhMJOry0PmX39LhN+BBMGxyxy9JWzQCMG1v+5XaCfAVIrYZIV0Ty+vD/kJJ+APP 8rtX0g8KBnZiyUd5mrex1WzCeDmMMbWJ3Ku+8QlTq/p5jxSt7HZcv7xprxUf0/vL3H kTn/S4SxAcl7yTudiLbqdDNH3gBqt6BK2fx2x2Fk= From: Clemens Gruber To: linux-pwm@vger.kernel.org Cc: Thierry Reding , u.kleine-koenig@pengutronix.de, Lee Jones , linux-kernel@vger.kernel.org, Sven Van Asbroeck , Mika Westerberg , David Jander , Clemens Gruber Subject: [PATCH v2 3/4] pwm: pca9685: Support staggered output ON times Date: Mon, 23 Nov 2020 17:36:22 +0100 Message-Id: <20201123163622.166048-3-clemens.gruber@pqgruber.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201123163622.166048-1-clemens.gruber@pqgruber.com> References: <20201123163622.166048-1-clemens.gruber@pqgruber.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The PCA9685 supports staggered LED output ON times to minimize current surges and reduce EMI. When this new option is enabled, the ON times of each channel are delayed by channel number x counter range / 16, which avoids asserting all enabled outputs at the same counter value while still maintaining the configured duty cycle of each output. Signed-off-by: Clemens Gruber --- Changes since v1: - Rebased drivers/pwm/pwm-pca9685.c | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c index eaeadfa853cf..c22268b63fcc 100644 --- a/drivers/pwm/pwm-pca9685.c +++ b/drivers/pwm/pwm-pca9685.c @@ -75,6 +75,7 @@ struct pca9685 { struct pwm_chip chip; struct regmap *regmap; int prescale; + bool staggered_outputs; #if IS_ENABLED(CONFIG_GPIOLIB) struct mutex lock; struct gpio_chip gpio; @@ -350,7 +351,7 @@ static int pca9685_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, { struct pca9685 *pca = to_pca(chip); unsigned long long duty, prescale; - unsigned int reg; + unsigned int on, off, reg; if (state->polarity != PWM_POLARITY_NORMAL) return -EOPNOTSUPP; @@ -386,6 +387,32 @@ static int pca9685_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, duty = (PCA9685_COUNTER_RANGE - 1) * state->duty_cycle; duty = DIV_ROUND_UP_ULL(duty, state->period); + if (pca->staggered_outputs) { + if (pwm->hwpwm < PCA9685_MAXCHAN) { + /* + * To reduce EMI, the ON times of each channel are + * spread out evenly within the counter range, while + * still maintaining the configured duty cycle + */ + on = pwm->hwpwm * PCA9685_COUNTER_RANGE / + PCA9685_MAXCHAN; + off = (on + duty) % PCA9685_COUNTER_RANGE; + regmap_write(pca->regmap, LED_N_ON_L(pwm->hwpwm), + on & 0xff); + regmap_write(pca->regmap, LED_N_ON_H(pwm->hwpwm), + (on >> 8) & 0xf); + regmap_write(pca->regmap, LED_N_OFF_L(pwm->hwpwm), + off & 0xff); + regmap_write(pca->regmap, LED_N_OFF_H(pwm->hwpwm), + (off >> 8) & 0xf); + return 0; + } + + /* No staggering possible if "all LEDs" channel is used */ + regmap_write(pca->regmap, PCA9685_ALL_LED_ON_L, 0); + regmap_write(pca->regmap, PCA9685_ALL_LED_ON_H, 0); + } + if (pwm->hwpwm >= PCA9685_MAXCHAN) reg = PCA9685_ALL_LED_OFF_L; else @@ -489,6 +516,9 @@ static int pca9685_pwm_probe(struct i2c_client *client, regmap_write(pca->regmap, PCA9685_MODE2, reg); + pca->staggered_outputs = device_property_read_bool( + &client->dev, "staggered-outputs"); + /* Disable all LED ALLCALL and SUBx addresses to avoid bus collisions */ regmap_read(pca->regmap, PCA9685_MODE1, ®); reg &= ~(MODE1_ALLCALL | MODE1_SUB1 | MODE1_SUB2 | MODE1_SUB3); @@ -497,6 +527,9 @@ static int pca9685_pwm_probe(struct i2c_client *client, /* Reset OFF registers to HW default (only full OFF bit is set) */ regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_L, 0); regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_H, LED_FULL); + /* Reset ON registers to HW default */ + regmap_write(pca->regmap, PCA9685_ALL_LED_ON_L, 0); + regmap_write(pca->regmap, PCA9685_ALL_LED_ON_H, 0); pca->chip.ops = &pca9685_pwm_ops; /* Add an extra channel for ALL_LED */ -- 2.29.2