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Date: Wed, 16 Dec 2020 22:58:07 -0500
From: Sven Van Asbroeck <thesven73@...il.com>
To: Clemens Gruber <clemens.gruber@...ruber.com>
Cc: linux-pwm@...r.kernel.org,
Thierry Reding <thierry.reding@...il.com>,
Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>, Lee Jones <lee.jones@...aro.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Mika Westerberg <mika.westerberg@...ux.intel.com>,
David Jander <david@...tonic.nl>
Subject: Re: [PATCH v5 1/7] pwm: pca9685: Switch to atomic API
Hi Clemens, this looks compact, simple and neat. I like it a lot !!
Few very minor nits below.
On Wed, Dec 16, 2020 at 7:53 AM Clemens Gruber
<clemens.gruber@...ruber.com> 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
>
> Signed-off-by: Clemens Gruber <clemens.gruber@...ruber.com>
> ---
> Changes since v4:
> - Patches split up
> - Use a single set_duty function
> - Improve readability / new macros
> - Added a patch to restrict prescale changes to the first user
>
> Changes since v3:
> - Refactoring: Extracted common functions
> - Read prescale register value instead of caching it
> - Return all zeros and disabled for "all LEDs" channel state
> - Improved duty calculation / mapping to 0..4096
>
> 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 | 253 +++++++++++++-------------------------
> 1 file changed, 87 insertions(+), 166 deletions(-)
>
> diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
> index 4a55dc18656c..1b5b5fb93b43 100644
> --- a/drivers/pwm/pwm-pca9685.c
> +++ b/drivers/pwm/pwm-pca9685.c
> @@ -51,7 +51,6 @@
> #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
> @@ -71,10 +70,14 @@
> #define LED_N_OFF_H(N) (PCA9685_LEDX_OFF_H + (4 * (N)))
> #define LED_N_OFF_L(N) (PCA9685_LEDX_OFF_L + (4 * (N)))
>
> +#define REG_ON_H(C) ((C) >= PCA9685_MAXCHAN ? PCA9685_ALL_LED_ON_H : LED_N_ON_H((C)))
> +#define REG_ON_L(C) ((C) >= PCA9685_MAXCHAN ? PCA9685_ALL_LED_ON_L : LED_N_ON_L((C)))
> +#define REG_OFF_H(C) ((C) >= PCA9685_MAXCHAN ? PCA9685_ALL_LED_OFF_H : LED_N_OFF_H((C)))
> +#define REG_OFF_L(C) ((C) >= PCA9685_MAXCHAN ? PCA9685_ALL_LED_OFF_L : LED_N_OFF_L((C)))
Yes !!
> +
> struct pca9685 {
> struct pwm_chip chip;
> struct regmap *regmap;
> - int period_ns;
> #if IS_ENABLED(CONFIG_GPIOLIB)
> struct mutex lock;
> struct gpio_chip gpio;
> @@ -87,6 +90,49 @@ static inline struct pca9685 *to_pca(struct pwm_chip *chip)
> return container_of(chip, struct pca9685, chip);
> }
>
> +static void pca9685_pwm_set_duty(struct pca9685 *pca, int channel, unsigned int duty)
> +{
Add brief function documentation to clarify that 'duty' sets the duty cycle
_ratio_ to 'duty/4096' on ? I.e.
duty == 2048 => duty cycle ratio = 2048/4096 = 50% on
duty == 4096 => duty cycle ratio = 4096/4086 = 100% on etc
> + if (duty == 0) {
> + /* Set the full OFF bit, which has the highest precedence */
> + regmap_write(pca->regmap, REG_OFF_H(channel), LED_FULL);
> + } 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);
> + }
> +}
> +
> +static unsigned int pca9685_pwm_get_duty(struct pca9685 *pca, int channel)
> +{
> + unsigned int off_h, 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) {
I believe this may trigger bots which are monitoring patches on LKML:
if regmap_read() somehow fails, off_h will be used uninitialized.
Prevent by initializing off_h and val?
> + /* Full OFF bit is set */
> + return 0;
> + }
> +
> + regmap_read(pca->regmap, LED_N_ON_H(channel), &val);
> + if (val & 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);
> +}
> +
> #if IS_ENABLED(CONFIG_GPIOLIB)
> static bool pca9685_pwm_test_and_set_inuse(struct pca9685 *pca, int pwm_idx)
> {
> @@ -138,34 +184,23 @@ static int pca9685_pwm_gpio_request(struct gpio_chip *gpio, unsigned int offset)
> static int pca9685_pwm_gpio_get(struct gpio_chip *gpio, unsigned int offset)
> {
> struct pca9685 *pca = gpiochip_get_data(gpio);
> - struct pwm_device *pwm = &pca->chip.pwms[offset];
> - unsigned int value;
>
> - regmap_read(pca->regmap, LED_N_ON_H(pwm->hwpwm), &value);
> -
> - return value & LED_FULL;
> + return pca9685_pwm_get_duty(pca, offset) != 0;
> }
>
> 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);
> + pca9685_pwm_set_duty(pca, offset, value ? PCA9685_COUNTER_RANGE : 0);
> }
>
> 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_set_duty(pca, offset, 0);
> pm_runtime_put(pca->chip.dev);
> pca9685_pwm_clear_inuse(pca, offset);
> }
> @@ -246,167 +281,56 @@ 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 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 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 (prescale >= PCA9685_PRESCALE_MIN &&
> - prescale <= PCA9685_PRESCALE_MAX) {
> - /*
> - * Putting the chip briefly into SLEEP mode
> - * at this point won't interfere with the
> - * pm_runtime framework, because the pm_runtime
> - * state is guaranteed active here.
> - */
> - /* Put chip into sleep mode */
> - pca9685_set_sleep_mode(pca, true);
> -
> - /* Change the chip-wide output frequency */
> - regmap_write(pca->regmap, PCA9685_PRESCALE, prescale);
> -
> - /* Wake the chip up */
> - pca9685_set_sleep_mode(pca, false);
> -
> - pca->period_ns = period_ns;
> - } else {
> - dev_err(chip->dev,
> - "prescaler not set: period out of bounds!\n");
> - return -EINVAL;
> - }
> - }
> + unsigned long long duty, prescale;
> + unsigned int val = 0;
>
> - if (duty_ns < 1) {
> - if (pwm->hwpwm >= PCA9685_MAXCHAN)
> - reg = PCA9685_ALL_LED_OFF_H;
> - else
> - reg = LED_N_OFF_H(pwm->hwpwm);
> + if (state->polarity != PWM_POLARITY_NORMAL)
> + return -EOPNOTSUPP;
>
> - regmap_write(pca->regmap, reg, LED_FULL);
> -
> - return 0;
> + prescale = DIV_ROUND_CLOSEST_ULL(PCA9685_OSC_CLOCK_MHZ * state->period,
> + PCA9685_COUNTER_RANGE * 1000) - 1;
> + if (prescale < PCA9685_PRESCALE_MIN || prescale > PCA9685_PRESCALE_MAX) {
> + dev_err(chip->dev, "prescaler not set: period out of bounds!\n");
would "pwm not changed: period out of bounds" be a clearer error message here?
> + return -EINVAL;
> }
>
> - 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);
> + duty = PCA9685_COUNTER_RANGE * state->duty_cycle;
> + duty = DIV_ROUND_CLOSEST_ULL(duty, state->period);
>
> + if (!state->enabled || duty < 1) {
> + pca9685_pwm_set_duty(pca, pwm->hwpwm, 0);
> + return 0;
> + } else if (duty == PCA9685_COUNTER_RANGE) {
> + pca9685_pwm_set_duty(pca, pwm->hwpwm, duty);
> return 0;
> }
>
> - duty = PCA9685_COUNTER_RANGE * (unsigned long long)duty_ns;
> - duty = DIV_ROUND_UP_ULL(duty, period_ns);
> -
> - if (pwm->hwpwm >= PCA9685_MAXCHAN)
> - reg = PCA9685_ALL_LED_OFF_L;
> - else
> - reg = LED_N_OFF_L(pwm->hwpwm);
> -
> - regmap_write(pca->regmap, reg, (int)duty & 0xff);
> -
> - if (pwm->hwpwm >= PCA9685_MAXCHAN)
> - reg = PCA9685_ALL_LED_OFF_H;
> - else
> - reg = LED_N_OFF_H(pwm->hwpwm);
> -
> - regmap_write(pca->regmap, reg, ((int)duty >> 8) & 0xf);
> -
> - /* Clear the full ON bit, otherwise the set OFF time has no effect */
> - 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);
> -
> - 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);
> + regmap_read(pca->regmap, PCA9685_PRESCALE, &val);
> + if (prescale != val) {
> + /*
> + * Putting the chip briefly into SLEEP mode
> + * at this point won't interfere with the
> + * pm_runtime framework, because the pm_runtime
> + * state is guaranteed active here.
> + */
> + /* Put chip into sleep mode */
> + pca9685_set_sleep_mode(pca, true);
>
> - /*
> - * 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);
> + /* Change the chip-wide output frequency */
> + regmap_write(pca->regmap, PCA9685_PRESCALE, (int)prescale);
>
> - regmap_update_bits(pca->regmap, reg, LED_FULL, 0x0);
> + /* Wake the chip up */
> + pca9685_set_sleep_mode(pca, false);
> + }
>
> + pca9685_pwm_set_duty(pca, pwm->hwpwm, duty);
> 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 +346,13 @@ 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_set_duty(pca, pwm->hwpwm, 0);
> 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,
> + .apply = pca9685_pwm_apply,
> .request = pca9685_pwm_request,
> .free = pca9685_pwm_free,
> .owner = THIS_MODULE,
> @@ -461,7 +383,6 @@ static int pca9685_pwm_probe(struct i2c_client *client,
> ret);
> return ret;
> }
> - pca->period_ns = PCA9685_DEFAULT_PERIOD;
>
> i2c_set_clientdata(client, pca);
>
> --
> 2.29.2
>
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