Re: [RESEND 08/11] pwm: sti: Add support for PWM Capture IRQs

Thierry Reding
2016-04-12T10:35:26Z

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On Wed, Mar 02, 2016 at 03:32:06PM +0000, Lee Jones wrote:
[...]
> diff --git a/drivers/pwm/pwm-sti.c b/drivers/pwm/pwm-sti.c
[...]
> +static irqreturn_t sti_pwm_interrupt(int irq, void *data)
> +{
> + struct sti_pwm_chip *pc = data;
> + struct device *dev = pc->dev;
> + struct sti_cpt_data *d;
> + int channel;
> + int cpt_int_stat;
> + int reg;
> + int ret = IRQ_NONE;
> +
> + ret = regmap_field_read(pc->pwm_cpt_int_stat, &cpt_int_stat);
> + if (ret)
> + return ret;
> +
> + while (cpt_int_stat) {
> + channel = ffs(cpt_int_stat) - 1;
> +
> + d = pc->cpt_data[channel];
> +
> + /*
> + * Capture input:
> + * _______ _______
> + * | | | |
> + * __| |_________________| |________
> + * ^0 ^1 ^2
> + *
> + * Capture start by the first available rising edge
> + * When a capture event occurs, capture value (CPT_VALx)
> + * is stored, index incremented, capture edge changed.
> + *
> + * After the capture, if the index > 1, we have collected
> + * the necessary data so we signal the thread waiting for it
> + * and disable the capture by setting capture edge to none
> + *
> + */

How do you deal with the situation where someone will stop the PWM
signal half-way in? That is, suppose you've got events for the first and
second snapshots (0 and 1) and then someone stops the PWM and the event
for snapshot 2 never happens, how does the code recover?

> +
> + regmap_read(pc->regmap,
> + PWM_CPT_VAL(channel), &d->snapshot[d->index]);
> +
> + switch (d->index) {
> + case 0:
> + case 1:
> + regmap_read(pc->regmap, PWM_CPT_EDGE(channel), &reg);
> + reg ^= PWM_CPT_EDGE_MASK;
> + regmap_write(pc->regmap, PWM_CPT_EDGE(channel), reg);
> +
> + d->index++;
> + break;
> + case 2:
> + regmap_write(pc->regmap,
> + PWM_CPT_EDGE(channel), CPT_EDGE_DISABLED);
> + wake_up(&d->wait);
> + break;
> + default:
> + dev_err(dev, "Internal error\n");
> + }
> +
> + clear_bit(channel, (unsigned long int *)&cpt_int_stat);

clear_bit() is a little unusual to use on regular data types, as
evidenced by the need for the goofy cast here.

> +
> + ret = IRQ_HANDLED;
> + }
> +
> + /* Just ACK everything */
> + regmap_write(pc->regmap, PWM_INT_ACK, PWM_INT_ACK_MASK);
> +
> + return ret;
> +}
> +
> static int sti_pwm_probe_dt(struct sti_pwm_chip *pc)
> {
> struct device *dev = pc->dev;
> @@ -354,6 +425,11 @@ static int sti_pwm_probe_dt(struct sti_pwm_chip *pc)
> if (IS_ERR(pc->pwm_cpt_int_en))
> return PTR_ERR(pc->pwm_cpt_int_en);
>
> + pc->pwm_cpt_int_stat = devm_regmap_field_alloc(dev, pc->regmap,
> + reg_fields[PWM_CPT_INT_STAT]);
> + if (IS_ERR(pc->pwm_cpt_int_stat))
> + return PTR_ERR(pc->pwm_cpt_int_stat);
> +
> return 0;
> }
>
> @@ -371,7 +447,7 @@ static int sti_pwm_probe(struct platform_device *pdev)
> struct sti_pwm_chip *pc;
> struct resource *res;
> unsigned int chan;
> - int ret;
> + int ret, irq;
>
> pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
> if (!pc)
> @@ -392,6 +468,19 @@ static int sti_pwm_probe(struct platform_device *pdev)
> if (IS_ERR(pc->regmap))
> return PTR_ERR(pc->regmap);
>
> + irq = platform_get_irq(pdev, 0);
> + if (irq < 0) {
> + dev_err(&pdev->dev, "Failed to obtain IRQ\n");
> + return -ENODEV;
> + }

I think you need to propagate the return value of platform_get_irq()
here.

> +
> + ret = devm_request_irq(&pdev->dev, irq, sti_pwm_interrupt,
> + 0, pdev->name, (void *) pc);

No need for the explicit cast to void *.

Thierry

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