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,URIBL_BLOCKED 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 AA94DC5519F for ; Wed, 25 Nov 2020 08:35:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2A9F3206F9 for ; Wed, 25 Nov 2020 08:35:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=pqgruber.com header.i=@pqgruber.com header.b="LVkGbP0k" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727375AbgKYIfN (ORCPT ); Wed, 25 Nov 2020 03:35:13 -0500 Received: from mail.pqgruber.com ([52.59.78.55]:60496 "EHLO mail.pqgruber.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725845AbgKYIfN (ORCPT ); Wed, 25 Nov 2020 03:35:13 -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 AC5CBC81EEB; Wed, 25 Nov 2020 09:35:09 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pqgruber.com; s=mail; t=1606293310; bh=5duKXyaDd7jvxQhCVTYur6RBOBqv6fBBF5W6WoCVxU8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LVkGbP0kTT3hgAAudenMGeZGVDfH9yT/ZX9mciaq5Z6o/YLfMIy113PfGsS4Zz18Y MsYlpO8wTQeGuWueXESTMtB6DK+hb52lHQgrrElUM7/qMqxf+YW4NBjt4jhw1VqyfG xL2ZEoQQZDV4amD31hAcAGI1hTPSlY2oKGGEPwtA= Date: Wed, 25 Nov 2020 09:35:08 +0100 From: Clemens Gruber To: Sven Van Asbroeck Cc: linux-pwm@vger.kernel.org, Thierry Reding , Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Lee Jones , Linux Kernel Mailing List , Mika Westerberg , David Jander Subject: Re: [PATCH v3 1/4] pwm: pca9685: Switch to atomic API Message-ID: References: <20201124181013.162176-1-clemens.gruber@pqgruber.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 24, 2020 at 10:49:27PM -0500, Sven Van Asbroeck wrote: > Hi Clemens, I checked the patch against the datasheet register definitions. > More constructive feedback below. > > On Tue, Nov 24, 2020 at 1:10 PM Clemens Gruber > wrote: > > > > The switch to the atomic API goes hand in hand with a few fixes to > > previously experienced issues: > > - The duty cycle is no longer lost after disable/enable (previously the > > OFF registers were cleared in disable and the user was required to > > call config to restore the duty cycle settings) > > - If one sets a period resulting in the same prescale register value, > > the sleep and write to the register is now skipped > > - The prescale register is now set to the default value in probe. On > > systems without CONFIG_PM, the chip is woken up at probe time. > > > > The hardware readout may return slightly different values than those > > that were set in apply due to the limited range of possible prescale and > > counter register values. If one channel is reconfigured with new duty > > cycle and period, the others will keep the same relative duty cycle to > > period ratio as they had before, even though the per-chip / global > > frequency changed. (The PCA9685 has only one prescaler!) > > > > Note that although the datasheet mentions 200 Hz as default frequency > > when using the internal 25 MHz oscillator, the calculated period from > > the default prescaler register setting of 30 is 5079040ns. > > > > Signed-off-by: Clemens Gruber > > --- > > Changes since v2: > > - Always set default prescale value in probe > > - Simplified probe code > > - Inlined functions with one callsite > > > > Changes since v1: > > - Fixed a logic error > > - Impoved PM runtime handling and fixed !CONFIG_PM > > - Write default prescale reg value if invalid in probe > > - Reuse full_off/_on functions throughout driver > > - Use cached prescale value whenever possible > > > > drivers/pwm/pwm-pca9685.c | 251 +++++++++++++++++++------------------- > > 1 file changed, 128 insertions(+), 123 deletions(-) > > > > diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c > > index 4a55dc18656c..4cfbf1467f15 100644 > > --- a/drivers/pwm/pwm-pca9685.c > > +++ b/drivers/pwm/pwm-pca9685.c > > @@ -47,11 +47,11 @@ > > #define PCA9685_ALL_LED_OFF_H 0xFD > > #define PCA9685_PRESCALE 0xFE > > > > +#define PCA9685_PRESCALE_DEF 0x1E /* => default frequency of ~200 Hz */ > > #define PCA9685_PRESCALE_MIN 0x03 /* => max. frequency of 1526 Hz */ > > #define PCA9685_PRESCALE_MAX 0xFF /* => min. frequency of 24 Hz */ > > > > #define PCA9685_COUNTER_RANGE 4096 > > -#define PCA9685_DEFAULT_PERIOD 5000000 /* Default period_ns = 1/200 Hz */ > > #define PCA9685_OSC_CLOCK_MHZ 25 /* Internal oscillator with 25 MHz */ > > > > #define PCA9685_NUMREGS 0xFF > > @@ -74,7 +74,7 @@ > > struct pca9685 { > > struct pwm_chip chip; > > struct regmap *regmap; > > - int period_ns; > > + int prescale; > > #if IS_ENABLED(CONFIG_GPIOLIB) > > struct mutex lock; > > struct gpio_chip gpio; > > @@ -87,6 +87,54 @@ static inline struct pca9685 *to_pca(struct pwm_chip *chip) > > return container_of(chip, struct pca9685, chip); > > } > > > > +static void pca9685_pwm_full_off(struct pca9685 *pca, int index) > > +{ > > + int reg; > > + > > + /* > > + * Set the full OFF bit to cause the PWM channel to be always off. > > + * The full OFF bit has precedence over the other register values. > > + */ > > + > > + if (index >= PCA9685_MAXCHAN) > > + reg = PCA9685_ALL_LED_OFF_H; > > + else > > + reg = LED_N_OFF_H(index); > > + > > + regmap_write(pca->regmap, reg, LED_FULL); > > +} > > + > > +static void pca9685_pwm_full_on(struct pca9685 *pca, int index) > > +{ > > + int reg; > > + > > + /* > > + * Clear the OFF registers (including the full OFF bit) and set > > + * the full ON bit to cause the PWM channel to be always on. > > + */ > > + > > + if (index >= PCA9685_MAXCHAN) > > + reg = PCA9685_ALL_LED_OFF_L; > > + else > > + reg = LED_N_OFF_L(index); > > + > > + regmap_write(pca->regmap, reg, 0); > > + > > + if (index >= PCA9685_MAXCHAN) > > + reg = PCA9685_ALL_LED_OFF_H; > > + else > > + reg = LED_N_OFF_H(index); > > + > > + regmap_write(pca->regmap, reg, 0); > > + > > + if (index >= PCA9685_MAXCHAN) > > + reg = PCA9685_ALL_LED_ON_H; > > + else > > + reg = LED_N_ON_H(index); > > + > > + regmap_write(pca->regmap, reg, LED_FULL); > > +} > > + > > #if IS_ENABLED(CONFIG_GPIOLIB) > > static bool pca9685_pwm_test_and_set_inuse(struct pca9685 *pca, int pwm_idx) > > { > > @@ -141,31 +189,27 @@ static int pca9685_pwm_gpio_get(struct gpio_chip *gpio, unsigned int offset) > > struct pwm_device *pwm = &pca->chip.pwms[offset]; > > unsigned int value; > > > > - regmap_read(pca->regmap, LED_N_ON_H(pwm->hwpwm), &value); > > + regmap_read(pca->regmap, LED_N_OFF_H(pwm->hwpwm), &value); > > > > - return value & LED_FULL; > > + return !(value & LED_FULL); > > } > > > > static void pca9685_pwm_gpio_set(struct gpio_chip *gpio, unsigned int offset, > > int value) > > { > > struct pca9685 *pca = gpiochip_get_data(gpio); > > - struct pwm_device *pwm = &pca->chip.pwms[offset]; > > - unsigned int on = value ? LED_FULL : 0; > > - > > - /* Clear both OFF registers */ > > - regmap_write(pca->regmap, LED_N_OFF_L(pwm->hwpwm), 0); > > - regmap_write(pca->regmap, LED_N_OFF_H(pwm->hwpwm), 0); > > > > - /* Set the full ON bit */ > > - regmap_write(pca->regmap, LED_N_ON_H(pwm->hwpwm), on); > > + if (value) > > + pca9685_pwm_full_on(pca, offset); > > + else > > + pca9685_pwm_full_off(pca, offset); > > } > > > > static void pca9685_pwm_gpio_free(struct gpio_chip *gpio, unsigned int offset) > > { > > struct pca9685 *pca = gpiochip_get_data(gpio); > > > > - pca9685_pwm_gpio_set(gpio, offset, 0); > > + pca9685_pwm_full_off(pca, offset); > > pm_runtime_put(pca->chip.dev); > > pca9685_pwm_clear_inuse(pca, offset); > > } > > @@ -246,18 +290,53 @@ static void pca9685_set_sleep_mode(struct pca9685 *pca, bool enable) > > } > > } > > > > -static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > > - int duty_ns, int period_ns) > > +static void pca9685_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, > > + struct pwm_state *state) > > +{ > > + struct pca9685 *pca = to_pca(chip); > > + unsigned int val, duty; > > + int reg; > > + > > + /* Calculate (chip-wide) period from cached prescale value */ > > + state->period = (PCA9685_COUNTER_RANGE * 1000 / PCA9685_OSC_CLOCK_MHZ) * > > + (pca->prescale + 1); > > + > > + /* The (per-channel) polarity is fixed */ > > + state->polarity = PWM_POLARITY_NORMAL; > > + > > + /* Read out current duty cycle and enabled state */ > > + reg = pwm->hwpwm >= PCA9685_MAXCHAN ? PCA9685_ALL_LED_OFF_H : > > + LED_N_OFF_H(pwm->hwpwm); > > + regmap_read(pca->regmap, reg, &val); > > The datasheet I found for this chip indicates that every ALL_LED_XXX register > is write-only. Those registers cannot be read back from the chip. > > Datasheet "Rev. 4 - 16 April 2015" Thanks, good catch! Would you agree that we should just return 0 duty cycle and disabled state if the "all LEDs" channel is used? > > > + duty = (val & 0xf) << 8; > > + > > + state->enabled = !(val & LED_FULL); > > + > > + reg = pwm->hwpwm >= PCA9685_MAXCHAN ? PCA9685_ALL_LED_OFF_L : > > + LED_N_OFF_L(pwm->hwpwm); > > + regmap_read(pca->regmap, reg, &val); > > + duty |= (val & 0xff); > > + > > + if (duty < PCA9685_COUNTER_RANGE) { > > How can duty >= 4096 ? > > > + duty *= state->period; > > + state->duty_cycle = duty / (PCA9685_COUNTER_RANGE - 1); > > is this calculation correct? > imagine led_on = 0 (default), and led_off = 4095 > then the led is off for one single tick per cycle > but the above formula would calculate it as full on (period == duty_cycle)? > > > + } else > > + state->duty_cycle = 0; > > what if the full on bit is set. would this function return the correct > duty cycle? No.. Sorry for not noticing this myself earlier! > > > > +} > > + > > +static int pca9685_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, > > + const struct pwm_state *state) > > { > > struct pca9685 *pca = to_pca(chip); > > - unsigned long long duty; > > + unsigned long long duty, prescale; > > unsigned int reg; > > - int prescale; > > > > - if (period_ns != pca->period_ns) { > > - prescale = DIV_ROUND_CLOSEST(PCA9685_OSC_CLOCK_MHZ * period_ns, > > - PCA9685_COUNTER_RANGE * 1000) - 1; > > + if (state->polarity != PWM_POLARITY_NORMAL) > > + return -EOPNOTSUPP; > > > > + prescale = DIV_ROUND_CLOSEST_ULL(PCA9685_OSC_CLOCK_MHZ * state->period, > > + PCA9685_COUNTER_RANGE * 1000) - 1; > > + if (prescale != pca->prescale) { > > if (prescale >= PCA9685_PRESCALE_MIN && > > prescale <= PCA9685_PRESCALE_MAX) { > > /* > > @@ -270,12 +349,12 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > > pca9685_set_sleep_mode(pca, true); > > > > /* Change the chip-wide output frequency */ > > - regmap_write(pca->regmap, PCA9685_PRESCALE, prescale); > > + regmap_write(pca->regmap, PCA9685_PRESCALE, (int)prescale); > > > > /* Wake the chip up */ > > pca9685_set_sleep_mode(pca, false); > > > > - pca->period_ns = period_ns; > > + pca->prescale = (int)prescale; > > } else { > > dev_err(chip->dev, > > "prescaler not set: period out of bounds!\n"); > > @@ -283,46 +362,18 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > > } > > } > > > > - if (duty_ns < 1) { > > - if (pwm->hwpwm >= PCA9685_MAXCHAN) > > - reg = PCA9685_ALL_LED_OFF_H; > > - else > > - reg = LED_N_OFF_H(pwm->hwpwm); > > - > > - regmap_write(pca->regmap, reg, LED_FULL); > > - > > + if (!state->enabled || state->duty_cycle < 1) { > > + pca9685_pwm_full_off(pca, pwm->hwpwm); > > return 0; > > } > > > > - if (duty_ns == period_ns) { > > - /* Clear both OFF registers */ > > - if (pwm->hwpwm >= PCA9685_MAXCHAN) > > - reg = PCA9685_ALL_LED_OFF_L; > > - else > > - reg = LED_N_OFF_L(pwm->hwpwm); > > - > > - regmap_write(pca->regmap, reg, 0x0); > > - > > - if (pwm->hwpwm >= PCA9685_MAXCHAN) > > - reg = PCA9685_ALL_LED_OFF_H; > > - else > > - reg = LED_N_OFF_H(pwm->hwpwm); > > - > > - regmap_write(pca->regmap, reg, 0x0); > > - > > - /* Set the full ON bit */ > > - if (pwm->hwpwm >= PCA9685_MAXCHAN) > > - reg = PCA9685_ALL_LED_ON_H; > > - else > > - reg = LED_N_ON_H(pwm->hwpwm); > > - > > - regmap_write(pca->regmap, reg, LED_FULL); > > - > > + if (state->duty_cycle == state->period) { > > + pca9685_pwm_full_on(pca, pwm->hwpwm); > > return 0; > > } > > > > - duty = PCA9685_COUNTER_RANGE * (unsigned long long)duty_ns; > > - duty = DIV_ROUND_UP_ULL(duty, period_ns); > > + duty = (PCA9685_COUNTER_RANGE - 1) * state->duty_cycle; > > + duty = DIV_ROUND_UP_ULL(duty, state->period); > > is there a rounding issue here? > imagine period = 10000, duty_cycle = 9999 > then the above formula says duty = 4095/4096 > but in reality the requested duty is much closer to full on! > same issue in reverse when period = 10000, duty_cycle = 1 > suggestion: do a DIV_ROUND_CLOSEST to calculate the closest duty, > then check against 0 and 4096 to see if full off / full on. > this also prevents led_off and led_on to be programmed with the same > value because of subtle rounding errors (not allowed as per datasheet) Yes that would be more accurate, good suggestion! > > > > > if (pwm->hwpwm >= PCA9685_MAXCHAN) > > reg = PCA9685_ALL_LED_OFF_L; > > @@ -349,64 +400,6 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > > return 0; > > } > > > > -static int pca9685_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm) > > -{ > > - struct pca9685 *pca = to_pca(chip); > > - unsigned int reg; > > - > > - /* > > - * The PWM subsystem does not support a pre-delay. > > - * So, set the ON-timeout to 0 > > - */ > > - if (pwm->hwpwm >= PCA9685_MAXCHAN) > > - reg = PCA9685_ALL_LED_ON_L; > > - else > > - reg = LED_N_ON_L(pwm->hwpwm); > > - > > - regmap_write(pca->regmap, reg, 0); > > - > > - if (pwm->hwpwm >= PCA9685_MAXCHAN) > > - reg = PCA9685_ALL_LED_ON_H; > > - else > > - reg = LED_N_ON_H(pwm->hwpwm); > > - > > - regmap_write(pca->regmap, reg, 0); > > - > > - /* > > - * Clear the full-off bit. > > - * It has precedence over the others and must be off. > > - */ > > - if (pwm->hwpwm >= PCA9685_MAXCHAN) > > - reg = PCA9685_ALL_LED_OFF_H; > > - else > > - reg = LED_N_OFF_H(pwm->hwpwm); > > - > > - regmap_update_bits(pca->regmap, reg, LED_FULL, 0x0); > > - > > - return 0; > > -} > > - > > -static void pca9685_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm) > > -{ > > - struct pca9685 *pca = to_pca(chip); > > - unsigned int reg; > > - > > - if (pwm->hwpwm >= PCA9685_MAXCHAN) > > - reg = PCA9685_ALL_LED_OFF_H; > > - else > > - reg = LED_N_OFF_H(pwm->hwpwm); > > - > > - regmap_write(pca->regmap, reg, LED_FULL); > > - > > - /* Clear the LED_OFF counter. */ > > - if (pwm->hwpwm >= PCA9685_MAXCHAN) > > - reg = PCA9685_ALL_LED_OFF_L; > > - else > > - reg = LED_N_OFF_L(pwm->hwpwm); > > - > > - regmap_write(pca->regmap, reg, 0x0); > > -} > > - > > static int pca9685_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm) > > { > > struct pca9685 *pca = to_pca(chip); > > @@ -422,15 +415,14 @@ static void pca9685_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm) > > { > > struct pca9685 *pca = to_pca(chip); > > > > - pca9685_pwm_disable(chip, pwm); > > + pca9685_pwm_full_off(pca, pwm->hwpwm); > > pm_runtime_put(chip->dev); > > pca9685_pwm_clear_inuse(pca, pwm->hwpwm); > > } > > > > static const struct pwm_ops pca9685_pwm_ops = { > > - .enable = pca9685_pwm_enable, > > - .disable = pca9685_pwm_disable, > > - .config = pca9685_pwm_config, > > + .get_state = pca9685_pwm_get_state, > > + .apply = pca9685_pwm_apply, > > .request = pca9685_pwm_request, > > .free = pca9685_pwm_free, > > .owner = THIS_MODULE, > > @@ -461,7 +453,6 @@ static int pca9685_pwm_probe(struct i2c_client *client, > > ret); > > return ret; > > } > > - pca->period_ns = PCA9685_DEFAULT_PERIOD; > > > > i2c_set_clientdata(client, pca); > > > > @@ -505,14 +496,21 @@ static int pca9685_pwm_probe(struct i2c_client *client, > > return ret; > > } > > > > - /* The chip comes out of power-up in the active state */ > > - pm_runtime_set_active(&client->dev); > > /* > > - * Enable will put the chip into suspend, which is what we > > - * want as all outputs are disabled at this point > > + * Always initialize with default prescale, but chip must be > > + * in sleep mode while changing prescaler. > > */ > > + pca9685_set_sleep_mode(pca, true); > > + pca->prescale = PCA9685_PRESCALE_DEF; > > + regmap_write(pca->regmap, PCA9685_PRESCALE, pca->prescale); > > + pm_runtime_set_suspended(&client->dev); > > pm_runtime_enable(&client->dev); > > > > + if (!IS_ENABLED(CONFIG_PM)) { > > + /* Wake the chip up on non-PM environments */ > > + pca9685_set_sleep_mode(pca, false); > > + } > > + > > return 0; > > } > > > > @@ -524,7 +522,14 @@ static int pca9685_pwm_remove(struct i2c_client *client) > > ret = pwmchip_remove(&pca->chip); > > if (ret) > > return ret; > > + > > pm_runtime_disable(&client->dev); > > + > > + if (!IS_ENABLED(CONFIG_PM)) { > > + /* Put chip in sleep state on non-PM environments */ > > + pca9685_set_sleep_mode(pca, true); > > + } > > + > > return 0; > > } > > > > -- > > 2.29.2 > >