Hello Clemens, On Mon, Apr 12, 2021 at 03:27:38PM +0200, 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 > - Previously, only the full ON bit was toggled in GPIO mode (and full > OFF cleared if set to high), which could result in both full OFF and > full ON not being set and on=0, off=0, which is not allowed according > to the datasheet > - The OFF registers were reset to 0 in probe, which could lead to the > forbidden on=0, off=0. Fixed by resetting to POR default (full OFF) > > Signed-off-by: Clemens Gruber <clemens.gru...@pqgruber.com> > --- > Changes since v7: > - Moved check for !state->enabled before prescaler configuration > - Removed unnecessary cast > - Use DIV_ROUND_DOWN in .apply > > Changes since v6: > - Order of a comparison switched for improved readability > > Changes since v5: > - Function documentation for set_duty > - Variable initializations > - Print warning if all LEDs channel > - Changed EOPNOTSUPP to EINVAL > - Improved error messages > - Register reset corrections moved to this patch > > 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 | 259 +++++++++++++------------------------- > 1 file changed, 89 insertions(+), 170 deletions(-) > > diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c > index 4a55dc18656c..827b57ced3c2 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)))
I'd like to see these named PCA9685_REG_ON_H etc.
> 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 +90,51 @@ static inline struct pca9685 *to_pca(struct pwm_chip *chip)
> return container_of(chip, struct pca9685, 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)
> +{
> + 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 = 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) {
> + /* 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;
> + }
> +
> + val = 0;
> + regmap_read(pca->regmap, LED_N_OFF_L(channel), &val);
I asked in the last round why you initialize val. You answered "just to
have it set to 0 in case regmap_read fails / val was not set." I wonder
if
ret = regmap_read(pca->regmap, LED_N_OFF_L(channel), &val);
if (!ret)
/*
val = 0
would be better then and also make the intention obvious.
> + 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 +186,23 @@ 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 +283,52 @@ 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 -EINVAL;
>
> - 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, "pwm not changed: period out of bounds!\n");
> + 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);
> -
> + if (!state->enabled) {
> + pca9685_pwm_set_duty(pca, pwm->hwpwm, 0);
> 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, prescale);
>
> - regmap_update_bits(pca->regmap, reg, LED_FULL, 0x0);
> + /* Wake the chip up */
> + pca9685_set_sleep_mode(pca, false);
> + }
>
> + duty = PCA9685_COUNTER_RANGE * state->duty_cycle;
> + duty = DIV_ROUND_DOWN_ULL(duty, state->period);
If you round down here you should probably also round down in the
calculation of prescale. Also note that you're losing precision by using
state->period.
Consider the following request: state->period = 4177921 [ns] +
state->duty_cycle = 100000 [ns], then we get
PRESCALE = round(25 * state->period / 4096000) - 1 = 25 and so an actual
period of 4096000 / 25 * (25 + 1) = 4259840 [ns]. If you now calculate
the duty using 4096 * 100000 / 4177920 = 98, this corresponds to an
actual duty cycle of 98 * 4259840 / 4096 = 101920 ns while you should
actually configure 96 to get 99840 ns.
So in the end I'd like to have the following:
PRESCALE = round-down(25 * state->period / 4096000) - 1
(to get the biggest period not bigger than state->period) and
duty = round-down(state->duty_cycle * 25 / ((PRESCALE + 1) * 1000))
(to get the biggest duty cycle not bigger than state->duty_cycle). With
the example above this yields
PRESCALE = 24
duty = 100
which results in
.period = 4096000 / 25 * 25 = 4096000 [ns]
.duty_cycle = 100000 [ns]
Now you have a mixture of old and new with no consistent behaviour. So
please either stick to the old behaviour or do it right immediately.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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