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,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 88034C2BB48 for ; Tue, 15 Dec 2020 21:30:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F1EF22B47 for ; Tue, 15 Dec 2020 21:30:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730125AbgLOV3u (ORCPT ); Tue, 15 Dec 2020 16:29:50 -0500 Received: from mail.pqgruber.com ([52.59.78.55]:54812 "EHLO mail.pqgruber.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728022AbgLOV3e (ORCPT ); Tue, 15 Dec 2020 16:29:34 -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 D25C6C727E0; Tue, 15 Dec 2020 22:28:45 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pqgruber.com; s=mail; t=1608067726; bh=VZT6wM9r2Vcydm8Etg5UEXrr3/TuRB6iASHSVNT69n0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OYytZ3Ozg0bwAs1c4x4HDReEKWcW8qeAAxnN9oR0wKYcOYviVx30pnk90aZoQG4os XoP5fJJBglXigKaX5zRyzE2syjtQ/63uNjzk6k1Nr0gOgY6bRJgoYgSWIeTAsXOcGf KPD8tUyY3A6IJkBcdWAYN1uo4bBFeuW1Pjq0zmqg= From: Clemens Gruber To: linux-pwm@vger.kernel.org Cc: Thierry Reding , u.kleine-koenig@pengutronix.de, Sven Van Asbroeck , Lee Jones , linux-kernel@vger.kernel.org, Mika Westerberg , David Jander , Clemens Gruber Subject: [PATCH v5 5/7] pwm: pca9685: Support staggered output ON times Date: Tue, 15 Dec 2020 22:22:26 +0100 Message-Id: <20201215212228.185517-5-clemens.gruber@pqgruber.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201215212228.185517-1-clemens.gruber@pqgruber.com> References: <20201215212228.185517-1-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 --- drivers/pwm/pwm-pca9685.c | 62 +++++++++++++++++++++++++++++++-------- 1 file changed, 50 insertions(+), 12 deletions(-) diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c index 38aadaf50996..ff916980de49 100644 --- a/drivers/pwm/pwm-pca9685.c +++ b/drivers/pwm/pwm-pca9685.c @@ -79,6 +79,7 @@ struct pca9685 { struct pwm_chip chip; struct regmap *regmap; + bool staggered_outputs; #if IS_ENABLED(CONFIG_GPIOLIB) struct mutex lock; struct gpio_chip gpio; @@ -93,45 +94,79 @@ static inline struct pca9685 *to_pca(struct pwm_chip *chip) static void pca9685_pwm_set_duty(struct pca9685 *pca, int channel, unsigned int duty) { + unsigned int on, off; + if (duty == 0) { /* Set the full OFF bit, which has the highest precedence */ regmap_write(pca->regmap, REG_OFF_H(channel), LED_FULL); + return; } else if (duty >= PCA9685_COUNTER_RANGE) { /* Set the full ON bit and clear the full OFF bit */ regmap_write(pca->regmap, REG_ON_H(channel), LED_FULL); regmap_write(pca->regmap, REG_OFF_H(channel), 0); - } else { - /* Set OFF time (clears the full OFF bit) */ - regmap_write(pca->regmap, REG_OFF_L(channel), duty & 0xff); - regmap_write(pca->regmap, REG_OFF_H(channel), (duty >> 8) & 0xf); - /* Clear the full ON bit */ - regmap_write(pca->regmap, REG_ON_H(channel), 0); + return; + } + + if (pca->staggered_outputs) { + if (channel < 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 = channel * PCA9685_COUNTER_RANGE / PCA9685_MAXCHAN; + off = (on + duty) % PCA9685_COUNTER_RANGE; + regmap_write(pca->regmap, REG_ON_L(channel), on & 0xff); + regmap_write(pca->regmap, REG_ON_H(channel), (on >> 8) & 0xf); + regmap_write(pca->regmap, REG_OFF_L(channel), off & 0xff); + regmap_write(pca->regmap, REG_OFF_H(channel), (off >> 8) & 0xf); + return; + } + /* No staggering possible if "all LEDs" channel is used */ + regmap_write(pca->regmap, PCA9685_ALL_LED_ON_L, 0); } + /* Set OFF time (clears the full OFF bit) */ + regmap_write(pca->regmap, REG_OFF_L(channel), duty & 0xff); + regmap_write(pca->regmap, REG_OFF_H(channel), (duty >> 8) & 0xf); + /* Clear the full ON bit */ + regmap_write(pca->regmap, REG_ON_H(channel), 0); } static unsigned int pca9685_pwm_get_duty(struct pca9685 *pca, int channel) { - unsigned int off_h, val; + unsigned int off, on, val; if (WARN_ON(channel >= PCA9685_MAXCHAN)) { /* Hardware readout not supported for "all LEDs" channel */ return 0; } - regmap_read(pca->regmap, LED_N_OFF_H(channel), &off_h); - if (off_h & LED_FULL) { + regmap_read(pca->regmap, LED_N_OFF_H(channel), &off); + if (off & LED_FULL) { /* Full OFF bit is set */ return 0; } - regmap_read(pca->regmap, LED_N_ON_H(channel), &val); - if (val & LED_FULL) { + regmap_read(pca->regmap, LED_N_ON_H(channel), &on); + if (on & LED_FULL) { /* Full ON bit is set */ return PCA9685_COUNTER_RANGE; } regmap_read(pca->regmap, LED_N_OFF_L(channel), &val); - return ((off_h & 0xf) << 8) | (val & 0xff); + off = ((off & 0xf) << 8) | (val & 0xff); + + if (pca->staggered_outputs) { + regmap_read(pca->regmap, LED_N_ON_L(channel), &val); + on = ((on & 0xf) << 8) | (val & 0xff); + + if (off >= on) + return off - on; + else + return off + PCA9685_COUNTER_RANGE - on; + } + + return off; } #if IS_ENABLED(CONFIG_GPIOLIB) @@ -442,6 +477,9 @@ 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, "nxp,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); -- 2.29.2