Re: [Stratos-dev] [PATCH V4 2/2] gpio: virtio: Add IRQ support

On 05-08-21, 15:10, Arnd Bergmann wrote:

I hope this can still be simplified by working out better which state
transitions are needed exactly. In particular, I would expect that we
can get away with not sending a VIRTIO_GPIO_MSG_IRQ_TYPE
for 'mask' state changes at all, but use that only for forcing 'enabled'
state changes.

Something like this ?

struct vgpio_irq_line {
	u8 type;
	bool masked;
	bool update_pending;
	bool queued;

	struct virtio_gpio_irq_request ireq ____cacheline_aligned;
	struct virtio_gpio_irq_response ires ____cacheline_aligned;
};

static void virtio_gpio_irq_disable(struct irq_data *d)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
	struct virtio_gpio *vgpio = gpiochip_get_data(gc);
	struct vgpio_irq_line *irq_line = &vgpio->irq_lines[d->hwirq];

	irq_line->masked = true;
	irq_line->update_pending = true;
}

static void virtio_gpio_irq_enable(struct irq_data *d)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
	struct virtio_gpio *vgpio = gpiochip_get_data(gc);
	struct vgpio_irq_line *irq_line = &vgpio->irq_lines[d->hwirq];

	irq_line->masked = false;
	irq_line->update_pending = true;

	/* Queue the buffer unconditionally on enable */
	virtio_gpio_irq_prepare(vgpio, d->hwirq);
}

static void virtio_gpio_irq_mask(struct irq_data *d)
{
	/* Nothing to do here */
}

static void virtio_gpio_irq_unmask(struct irq_data *d)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
	struct virtio_gpio *vgpio = gpiochip_get_data(gc);

	/* Queue the buffer unconditionally on unmask */
	virtio_gpio_irq_prepare(vgpio, d->hwirq);
}

static int virtio_gpio_irq_set_type(struct irq_data *d, unsigned int type)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
	struct virtio_gpio *vgpio = gpiochip_get_data(gc);
	struct vgpio_irq_line *irq_line = &vgpio->irq_lines[d->hwirq];

	switch (type) {
	case IRQ_TYPE_NONE:
		type = VIRTIO_GPIO_IRQ_TYPE_NONE;
		break;
	case IRQ_TYPE_EDGE_RISING:
		type = VIRTIO_GPIO_IRQ_TYPE_EDGE_RISING;
		break;
	case IRQ_TYPE_EDGE_FALLING:
		type = VIRTIO_GPIO_IRQ_TYPE_EDGE_FALLING;
		break;
	case IRQ_TYPE_EDGE_BOTH:
		type = VIRTIO_GPIO_IRQ_TYPE_EDGE_BOTH;
		break;
	case IRQ_TYPE_LEVEL_LOW:
		type = VIRTIO_GPIO_IRQ_TYPE_LEVEL_LOW;
		break;
	case IRQ_TYPE_LEVEL_HIGH:
		type = VIRTIO_GPIO_IRQ_TYPE_LEVEL_HIGH;
		break;
	default:
		dev_err(&vgpio->vdev->dev, "unsupported irq type: %u\n", type);
		return -EINVAL;
	}

	irq_line->type = type;
	irq_line->update_pending = true;

	return 0;
}

static void update_irq_type(struct virtio_gpio *vgpio, u16 gpio, u8 type)
{
	virtio_gpio_req(vgpio, VIRTIO_GPIO_MSG_IRQ_TYPE, gpio, type, NULL);
}

static void virtio_gpio_irq_bus_lock(struct irq_data *d)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
	struct virtio_gpio *vgpio = gpiochip_get_data(gc);

	mutex_lock(&vgpio->irq_lock);
}

static void virtio_gpio_irq_bus_sync_unlock(struct irq_data *d)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
	struct virtio_gpio *vgpio = gpiochip_get_data(gc);
	struct vgpio_irq_line *irq_line = &vgpio->irq_lines[d->hwirq];
	u8 type = irq_line->masked ? VIRTIO_GPIO_IRQ_TYPE_NONE : irq_line->type;

	if (irq_line->update_pending) {
		irq_line->update_pending = false;
		update_irq_type(vgpio, d->hwirq, type);
	}

	mutex_unlock(&vgpio->irq_lock);
}

static struct irq_chip vgpio_irq_chip = {
	.name			= "virtio-gpio",
	.irq_enable		= virtio_gpio_irq_enable,
	.irq_disable		= virtio_gpio_irq_disable,
	.irq_mask		= virtio_gpio_irq_mask,
	.irq_unmask		= virtio_gpio_irq_unmask,
	.irq_set_type		= virtio_gpio_irq_set_type,

	/* These are required to implement irqchip for slow busses */
	.irq_bus_lock		= virtio_gpio_irq_bus_lock,
	.irq_bus_sync_unlock	= virtio_gpio_irq_bus_sync_unlock,
};

One part that I think is missing though is remembering the case
when an eventq message came in after an interrupt got masked
when the message was already armed. In this case, the
virtio_gpio_event_vq() function would not call the irq handler,
but the subsequent "unmask" callback would need to arrange
having it called.

I will come back to this.

-- 
viresh
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