From patchwork Wed Nov 18 17:44:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Clemens Gruber X-Patchwork-Id: 1402436 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-pwm-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=pqgruber.com Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=pqgruber.com header.i=@pqgruber.com header.a=rsa-sha256 header.s=mail header.b=EwRi9o/I; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4Cbqvx5y9nz9sTL for ; Thu, 19 Nov 2020 04:45:17 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726505AbgKRRpJ (ORCPT ); Wed, 18 Nov 2020 12:45:09 -0500 Received: from mail.pqgruber.com ([52.59.78.55]:53842 "EHLO mail.pqgruber.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726504AbgKRRpJ (ORCPT ); Wed, 18 Nov 2020 12:45:09 -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 1F18FC7D0F7; Wed, 18 Nov 2020 18:45:07 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pqgruber.com; s=mail; t=1605721507; bh=Vd2Gr8YsjPn2h239nMG1j/VeOssRUKO75wDDPmdvDvo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EwRi9o/ITD1HtvB48kAD6kQ8ZS5PllEDKSmyoIZpx6XBFvDmMvkBsVFH3HZNr3hXg NtTMjFeLcGAUaamZe2Ag2JHfyP+tnHeQmMf7zC9/xJIn/hUM/2n8Pw5OjEMQjcikO6 rTXJt/ZJaehwb05LcXKIa5TYqQudHol7AL5V+ETE= 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 3/3] pwm: pca9685: Support staggered output ON times Date: Wed, 18 Nov 2020 18:44:17 +0100 Message-Id: <20201118174417.278011-3-clemens.gruber@pqgruber.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201118174417.278011-1-clemens.gruber@pqgruber.com> References: <20201118174417.278011-1-clemens.gruber@pqgruber.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-pwm@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 --- 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 88028222335f..95958b5cce0d 100644 --- a/drivers/pwm/pwm-pca9685.c +++ b/drivers/pwm/pwm-pca9685.c @@ -74,6 +74,7 @@ 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; @@ -348,7 +349,7 @@ 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; @@ -395,6 +396,32 @@ 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 @@ -494,6 +521,9 @@ 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); @@ -502,6 +532,9 @@ 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 */