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=-15.8 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 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 744D8C43460 for ; Mon, 12 Apr 2021 17:12:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51C7961206 for ; Mon, 12 Apr 2021 17:12:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243692AbhDLRMU (ORCPT ); Mon, 12 Apr 2021 13:12:20 -0400 Received: from mail.pqgruber.com ([52.59.78.55]:33300 "EHLO mail.pqgruber.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239716AbhDLRMT (ORCPT ); Mon, 12 Apr 2021 13:12:19 -0400 Received: from workstation.tuxnet (213-47-165-233.cable.dynamic.surfer.at [213.47.165.233]) by mail.pqgruber.com (Postfix) with ESMTPSA id 8292EC725CF; Mon, 12 Apr 2021 19:11:59 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pqgruber.com; s=mail; t=1618247519; bh=s70jJ6PUcq1vMW2f9OQQPQXe2SFSJs1hmfS8w1t+mBI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Ok66qAe83uGzzW0JSXD++tUQXyjBZbgHfcwj3mUqOUSEaGbg6ItOzfsMin32rAPlX C264jO/Zo2j03Q+dmoRm7Xubl0MqJ2vNTt/jbWMJRkbPKPIuhAVN6GPYt53EKLnO29 JayCN2TCfxYGa2JEfsXuyl6wFpZ9BCF9JH0r3/rs= Date: Mon, 12 Apr 2021 19:11:58 +0200 From: Clemens Gruber To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: linux-pwm@vger.kernel.org, Thierry Reding , Sven Van Asbroeck , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 6/8] pwm: pca9685: Support new PWM_USAGE_POWER flag Message-ID: References: <20210412132745.76609-1-clemens.gruber@pqgruber.com> <20210412132745.76609-6-clemens.gruber@pqgruber.com> <20210412163045.apgnac7atgpboths@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210412163045.apgnac7atgpboths@pengutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Mon, Apr 12, 2021 at 06:30:45PM +0200, Uwe Kleine-König wrote: > On Mon, Apr 12, 2021 at 03:27:43PM +0200, Clemens Gruber wrote: > > If PWM_USAGE_POWER is set on a PWM, the pca9685 driver will phase shift > > the individual channels relative to their channel number. This improves > > EMI because the enabled channels no longer turn on at the same time, > > while still maintaining the configured duty cycle / power output. > > > > Signed-off-by: Clemens Gruber > > --- > > drivers/pwm/pwm-pca9685.c | 63 ++++++++++++++++++++++++++++++--------- > > 1 file changed, 49 insertions(+), 14 deletions(-) > > > > diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c > > index 7f97965033e7..410b93b115dc 100644 > > --- a/drivers/pwm/pwm-pca9685.c > > +++ b/drivers/pwm/pwm-pca9685.c > > @@ -93,46 +93,76 @@ static inline struct pca9685 *to_pca(struct pwm_chip *chip) > > /* Helper function to set the duty cycle ratio to duty/4096 (e.g. duty=2048 -> 50%) */ > > static void pca9685_pwm_set_duty(struct pca9685 *pca, int channel, unsigned int duty) > > { > > + struct pwm_device *pwm = &pca->chip.pwms[channel]; > > + 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 (pwm->args.usage_power && channel < PCA9685_MAXCHAN) { > > + /* > > + * If PWM_USAGE_POWER is set on a PWM, the pca9685 > > + * driver will phase shift the individual channels > > + * relative to their channel number. > > + * This improves EMI because the enabled channels no > > + * longer turn on at the same time, while still > > + * maintaining the configured duty cycle / power output. > > + */ > > + on = channel * PCA9685_COUNTER_RANGE / PCA9685_MAXCHAN; > > + } else > > + on = 0; > > + > > + off = (on + duty) % PCA9685_COUNTER_RANGE; > > + > > + /* Set ON time (clears full ON bit) */ > > + regmap_write(pca->regmap, REG_ON_L(channel), on & 0xff); > > + regmap_write(pca->regmap, REG_ON_H(channel), (on >> 8) & 0xf); > > + /* Set OFF time (clears full OFF bit) */ > > + regmap_write(pca->regmap, REG_OFF_L(channel), off & 0xff); > > + regmap_write(pca->regmap, REG_OFF_H(channel), (off >> 8) & 0xf); > > } > > > > static unsigned int pca9685_pwm_get_duty(struct pca9685 *pca, int channel) > > { > > - unsigned int off_h = 0, val = 0; > > + struct pwm_device *pwm = &pca->chip.pwms[channel]; > > + unsigned int off = 0, on = 0, val = 0; > > > > if (WARN_ON(channel >= PCA9685_MAXCHAN)) { > > /* HW does not support reading state of "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; > > } > > > > - val = 0; > > regmap_read(pca->regmap, LED_N_OFF_L(channel), &val); > > - return ((off_h & 0xf) << 8) | (val & 0xff); > > + off = ((off & 0xf) << 8) | (val & 0xff); > > + if (!pwm->args.usage_power) > > + return off; > > + > > + /* Read ON register to calculate duty cycle of staggered output */ > > + val = 0; > > + regmap_read(pca->regmap, LED_N_ON_L(channel), &val); > > + on = ((on & 0xf) << 8) | (val & 0xff); > > + return (off - on) & (PCA9685_COUNTER_RANGE - 1); > > If LED_N_ON is != 0 but usage_power is false, the returned state is > bogus. If usage_power is false, LED_N_ON is guaranteed to be 0. It is reset to 0 in probe and never changed. Or did I miss something? > > > } > > > > #if IS_ENABLED(CONFIG_GPIOLIB) > > @@ -439,9 +469,11 @@ static int pca9685_pwm_probe(struct i2c_client *client, > > reg &= ~(MODE1_ALLCALL | MODE1_SUB1 | MODE1_SUB2 | MODE1_SUB3); > > regmap_write(pca->regmap, PCA9685_MODE1, reg); > > > > - /* Reset OFF registers to POR default */ > > + /* Reset OFF/ON registers to POR default */ > > regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_L, LED_FULL); > > regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_H, LED_FULL); > > + 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 */ > > @@ -450,6 +482,9 @@ static int pca9685_pwm_probe(struct i2c_client *client, > > pca->chip.dev = &client->dev; > > pca->chip.base = -1; > > > > + pca->chip.of_xlate = of_pwm_xlate_with_flags; > > + pca->chip.of_pwm_n_cells = 3; > > + > > Huh, you're incompatibly changing the device tree binding here. No, I don't think so: The third cell is optional with of_pwm_xlate_with_flags. So previous DTs with pwm-cells = <2> will still work. If you want to use the new flag for some PWMs you have to set pwm-cells to <3> and PWM_USAGE_POWER (or 0) in the third field at the consumer. This should not break backwards compatibility. Let me know if I missed something. Thanks for your review, Clemens