Hello, On Sun, Jun 21, 2020 at 12:42:17AM +0200, Jonathan Neuschäfer wrote: > The Netronix EC provides a PWM output, which is used for the backlight
s/,//
> on ebook readers. This patches adds a driver for the PWM output.
on *some* ebook readers
> +#define NTXEC_UNK_A 0xa1
> +#define NTXEC_UNK_B 0xa2
> +#define NTXEC_ENABLE 0xa3
> +#define NTXEC_PERIOD_LOW 0xa4
> +#define NTXEC_PERIOD_HIGH 0xa5
> +#define NTXEC_DUTY_LOW 0xa6
> +#define NTXEC_DUTY_HIGH 0xa7
> +
> +/*
> + * The time base used in the EC is 8MHz, or 125ns. Period and duty cycle are
> + * measured in this unit.
> + */
> +static int ntxec_pwm_config(struct pwm_chip *chip, struct pwm_device
> *pwm_dev,
> + int duty_ns, int period_ns)
> +{
> + struct ntxec_pwm *pwm = pwmchip_to_pwm(chip);
> + uint64_t duty = duty_ns;
> + uint64_t period = period_ns;
As you cannot use values bigger than 8191999 anyhow, I wonder why you
use a 64 bit type here.
> + int res = 0;
> +
> + do_div(period, 125);
Please use a define instead of plain 125.
> + if (period > 0xffff) {
> + dev_warn(pwm->dev,
> + "Period is not representable in 16 bits: %llu\n",
> period);
> + return -ERANGE;
> + }
> +
> + do_div(duty, 125);
> + if (duty > 0xffff) {
> + dev_warn(pwm->dev, "Duty cycle is not representable in 16 bits:
> %llu\n",
> + duty);
> + return -ERANGE;
> + }
This check isn't necessary as the pwm core ensures that duty <= period.
> + res |= ntxec_write8(pwm->ec, NTXEC_PERIOD_HIGH, period >> 8);
> + res |= ntxec_write8(pwm->ec, NTXEC_PERIOD_LOW, period);
> + res |= ntxec_write8(pwm->ec, NTXEC_DUTY_HIGH, duty >> 8);
> + res |= ntxec_write8(pwm->ec, NTXEC_DUTY_LOW, duty);
Does this complete the currently running period? Can it happen that a
new period starts between the first and the last write and so a mixed
period can be seen at the output?
> +
> + return (res < 0) ? -EIO : 0;
> +}
> +
> +static int ntxec_pwm_enable(struct pwm_chip *chip,
> + struct pwm_device *pwm_dev)
> +{
> + struct ntxec_pwm *pwm = pwmchip_to_pwm(chip);
> +
> + return ntxec_write8(pwm->ec, NTXEC_ENABLE, 1);
> +}
> +
> +static void ntxec_pwm_disable(struct pwm_chip *chip,
> + struct pwm_device *pwm_dev)
> +{
> + struct ntxec_pwm *pwm = pwmchip_to_pwm(chip);
> +
> + ntxec_write8(pwm->ec, NTXEC_ENABLE, 0);
> +}
> +
> +static struct pwm_ops ntxec_pwm_ops = {
> + .config = ntxec_pwm_config,
> + .enable = ntxec_pwm_enable,
> + .disable = ntxec_pwm_disable,
> + .owner = THIS_MODULE,
Please don't align the =, just a single space before them is fine.
More important: Please implement .apply() (and .get_state()) instead of
the old API. Also please enable PWM_DEBUG which might save us a review
iteration.
> +};
> +
> +static int ntxec_pwm_probe(struct platform_device *pdev)
> +{
> + struct ntxec *ec = dev_get_drvdata(pdev->dev.parent);
> + struct ntxec_pwm *pwm;
> + struct pwm_chip *chip;
> + int res;
> +
> + pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
> + if (!pwm)
> + return -ENOMEM;
> +
> + pwm->ec = ec;
> + pwm->dev = &pdev->dev;
> +
> + chip = &pwm->chip;
> + chip->dev = &pdev->dev;
> + chip->ops = &ntxec_pwm_ops;
> + chip->base = -1;
> + chip->npwm = 1;
> +
> + res = pwmchip_add(chip);
> + if (res < 0)
> + return res;
> +
> + platform_set_drvdata(pdev, pwm);
> +
> + res |= ntxec_write8(pwm->ec, NTXEC_ENABLE, 0);
> + res |= ntxec_write8(pwm->ec, NTXEC_UNK_A, 0xff);
> + res |= ntxec_write8(pwm->ec, NTXEC_UNK_B, 0xff);
> +
> + return (res < 0) ? -EIO : 0;
This is broken for several reasons:
- You're not supposed to modify the output in .probe
- if ntxec_write8 results in an error you keep the pwm registered.
- From the moment on pwmchip_add returns the callbacks can be called.
The calls to ntxec_write8 probably interfere here.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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