Hello,
On Thu, Oct 08, 2020 at 01:40:30AM +0800, vijayakannan.ayyathurai@xxxxxxxxx wrote:
> +static int keembay_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> + const struct pwm_state *state)
> +{
> + struct keembay_pwm *priv = to_keembay_pwm_dev(chip);
> + struct pwm_state current_state;
> + u16 pwm_h_count, pwm_l_count;
> + unsigned long long div;
> + unsigned long clk_rate;
> + u32 pwm_count = 0;
> +
> + if (state->polarity != PWM_POLARITY_NORMAL)
> + return -ENOSYS;
> +
> + keembay_pwm_update_bits(priv, KMB_PWM_LEADIN_MASK, 0,
> + KMB_PWM_LEADIN_OFFSET(pwm->hwpwm));
> +
> + keembay_pwm_get_state(chip, pwm, ¤t_state);
> +
> + if (!state->enabled) {
> + if (current_state.enabled)
> + keembay_pwm_disable(priv, pwm->hwpwm);
> + return 0;
> + }
> +
> + /*
> + * The upper 16 bits of the KMB_PWM_HIGHLOW_OFFSET register contain
> + * the high time of the waveform, while the last 16 bits contain
> + * the low time of the waveform, in terms of clock cycles.
> + *
> + * high time = clock rate * duty cycle
> + * low time = clock rate * (period - duty cycle)
> + */
> +
> + clk_rate = clk_get_rate(priv->clk);
> + /* Configure waveform high time */
> + div = clk_rate * state->duty_cycle;
> + div = DIV_ROUND_DOWN_ULL(div, NSEC_PER_SEC);
> + if (div > KMB_PWM_COUNT_MAX)
> + return -ERANGE;
> +
> + pwm_h_count = div;
> + /* Configure waveform low time */
> + div = clk_rate * (state->period - state->duty_cycle);
> + div = DIV_ROUND_DOWN_ULL(div, NSEC_PER_SEC - pwm_h_count);
In reply to your v7 I suggested the example:
clk_rate = 333334 [Hz]
state.duty_cycle = 1000500 [ns]
state.period = 2001000 [ns]
where the expected outcome is
pwm_h_count = 333
pwm_l_count = 334
. Please reread my feedback there. I tried to construct an example where
the value is more wrong, but with the constraint that pwm_h_count must
be <= KMB_PWM_COUNT_MAX this isn't easy. The best I could come up with
is:
clk_rate = 1000000000
state.duty_cycle = 65535 [ns]
state.period = 131070 [ns]
where the right value for pwm_l_count is 65535 while you calculate
65539 (and then quit with -ERANGE).
> + if (div > KMB_PWM_COUNT_MAX)
> + return -ERANGE;
> +
> + pwm_l_count = div;
> +
> + pwm_count = FIELD_PREP(KMB_PWM_HIGH_MASK, pwm_h_count) |
> + FIELD_PREP(KMB_PWM_LOW_MASK, pwm_l_count);
> +
> + writel(pwm_count, priv->base + KMB_PWM_HIGHLOW_OFFSET(pwm->hwpwm));
> +
> + if (state->enabled && !current_state.enabled)
> + keembay_pwm_enable(priv, pwm->hwpwm);
> +
> + return 0;
> +}
> +
> +static const struct pwm_ops keembay_pwm_ops = {
> + .owner = THIS_MODULE,
> + .apply = keembay_pwm_apply,
> + .get_state = keembay_pwm_get_state,
> +};
> +
> +static int keembay_pwm_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct keembay_pwm *priv;
> + int ret;
> +
> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + priv->clk = devm_clk_get(dev, NULL);
> + if (IS_ERR(priv->clk))
> + return dev_err_probe(dev, PTR_ERR(priv->clk), "Failed to get clock\n");
> +
> + ret = clk_prepare_enable(priv->clk);
> + if (ret)
> + return ret;
> +
> + priv->base = devm_platform_ioremap_resource(pdev, 0);
> + if (IS_ERR(priv->base)) {
> + clk_disable_unprepare(priv->clk);
> + return PTR_ERR(priv->base);
> + }
> +
> + priv->chip.base = -1;
> + priv->chip.dev = dev;
> + priv->chip.ops = &keembay_pwm_ops;
> + priv->chip.npwm = KMB_TOTAL_PWM_CHANNELS;
> +
> + ret = pwmchip_add(&priv->chip);
> + if (ret) {
> + dev_err(dev, "Failed to add PWM chip: %pe\n", ERR_PTR(ret));
> + clk_disable_unprepare(priv->clk);
> + return ret;
> + }
> +
> + platform_set_drvdata(pdev, priv);
> +
> + return 0;
> +}
> +
> +static int keembay_pwm_remove(struct platform_device *pdev)
> +{
> + struct keembay_pwm *priv = platform_get_drvdata(pdev);
> +
> + clk_disable_unprepare(priv->clk);
> +
> + return pwmchip_remove(&priv->chip);
You have to call pwmchip_remove first. Otherwise you're stopping the PWM
while the framework still believes everything to be fine.
> +}
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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