Hello Nicolas, On Mon, Jan 18, 2021 at 01:32:44PM +0100, Nicolas Saenz Julienne wrote: > diff --git a/drivers/pwm/pwm-raspberrypi-poe.c > b/drivers/pwm/pwm-raspberrypi-poe.c > new file mode 100644 > index 000000000000..ca845e8fabe6 > --- /dev/null > +++ b/drivers/pwm/pwm-raspberrypi-poe.c > @@ -0,0 +1,220 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright 2020 Nicolas Saenz Julienne <nsaenzjulie...@suse.de> > + * For more information on Raspberry Pi's PoE hat see: > + * https://www.raspberrypi.org/products/poe-hat/ > + * > + * Limitations: > + * - No disable bit, so a disabled PWM is simulated by duty_cycle 0 > + * - Only normal polarity > + * - Fixed 12.5 kHz period > + * > + * The current period is completed when HW is reconfigured.
nice.
> + */
> +
> [...]
> +static int raspberrypi_pwm_apply(struct pwm_chip *chip, struct pwm_device
> *pwm,
> + const struct pwm_state *state)
> +{
> + struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
> + unsigned int duty_cycle;
> + int ret;
> +
> + if (state->period < RPI_PWM_PERIOD_NS ||
> + state->polarity != PWM_POLARITY_NORMAL)
> + return -EINVAL;
> +
> + if (!state->enabled)
> + duty_cycle = 0;
> + else if (state->duty_cycle < RPI_PWM_PERIOD_NS)
> + duty_cycle = DIV_ROUND_DOWN_ULL(state->duty_cycle *
> RPI_PWM_MAX_DUTY,
> + RPI_PWM_PERIOD_NS);
> + else
> + duty_cycle = RPI_PWM_MAX_DUTY;
> +
> + if (duty_cycle == rpipwm->duty_cycle)
> + return 0;
> +
> + ret = raspberrypi_pwm_set_property(rpipwm->firmware,
> RPI_PWM_CUR_DUTY_REG,
> + duty_cycle);
> + if (ret) {
> + dev_err(chip->dev, "Failed to set duty cycle: %pe\n",
> + ERR_PTR(ret));
> + return ret;
> + }
> +
> + /*
> + * This sets the default duty cycle after resetting the board, we
> + * updated it every time to mimic Raspberry Pi's downstream's driver
> + * behaviour.
> + */
> + ret = raspberrypi_pwm_set_property(rpipwm->firmware,
> RPI_PWM_DEF_DUTY_REG,
> + duty_cycle);
> + if (ret) {
> + dev_err(chip->dev, "Failed to set default duty cycle: %pe\n",
> + ERR_PTR(ret));
> + return ret;
This only has an effect for the next reboot, right? If so I wonder if it
is a good idea in general. (Think: The current PWM setting enables a
motor that makes a self-driving car move at 100 km/h. Consider the rpi
crashes, do I want to car to pick up driving 100 km/h at power up even
before Linux is up again?) And if we agree it's a good idea: Should
raspberrypi_pwm_apply return 0 if setting the duty cycle succeeded and
only setting the default didn't?
Other than that the patch looks fine.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
signature.asc
Description: PGP signature
_______________________________________________ devel mailing list de...@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
