Date:   Wed, 09 Feb 2022 14:10:49 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Sander Vanheule <sander@...nheule.net>
Cc:     Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Birger Koblitz <mail@...ger-koblitz.de>,
        Bert Vermeulen <bert@...t.com>,
        John Crispin <john@...ozen.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] irqchip/realtek-rtl: use per-parent domains

On Sun, 06 Feb 2022 16:41:53 +0000,
Sander Vanheule <sander@...nheule.net> wrote:
> 
> The interrupt router can connect each of its inputs to one of the parent
> interrupts. These parent interrupts may be handled differently by their
> interrupt controller. SoC interrupts should be treated per-parent, to
> maintain this expected behaviour for routed child interrupts.
> 
> For example, it is possible that both networking interrupts and the
> system event timer interrupts are routed through this controller. Even
> under high network load, event timer interrupts should take precedence,
> which can be ensured by routing them to a higher priority parent.
> 
> Rework the driver to use a separate domain for each output, using all
> available parents interrupts (as specified in the devicetree). A
> per-parent mask of child interrupts is used to keep track of which
> domain should handle which interrupts.

So you are encoding a particular priority scheme in the device tree
even if this is really under SW control? That's pretty horrible.

> 
> Signed-off-by: Sander Vanheule <sander@...nheule.net>
> ---
>  drivers/irqchip/irq-realtek-rtl.c | 150 ++++++++++++++++++++++++------
>  1 file changed, 124 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-realtek-rtl.c b/drivers/irqchip/irq-realtek-rtl.c
> index 388f4a7bfb80..868eb9b25e84 100644
> --- a/drivers/irqchip/irq-realtek-rtl.c
> +++ b/drivers/irqchip/irq-realtek-rtl.c
> @@ -22,12 +22,22 @@
>  #define RTL_ICTL_IRR3		0x14
>  
>  #define RTL_ICTL_NUM_INPUTS	32
> +#define RTL_ICTL_NUM_OUTPUTS	15
>  
>  #define REG(x)		(realtek_ictl_base + x)
>  
>  static DEFINE_RAW_SPINLOCK(irq_lock);
>  static void __iomem *realtek_ictl_base;
>  
> +struct realtek_ictl_output {
> +	/* IRQ controller data */
> +	struct fwnode_handle *fwnode;
> +	/* Output specific data */
> +	unsigned int output_index;
> +	struct irq_domain *domain;
> +	u32 child_mask;
> +};
> +
>  /*
>   * IRR0-IRR3 store 4 bits per interrupt, but Realtek uses inverted numbering,
>   * placing IRQ 31 in the first four bits. A routing value of '0' means the
> @@ -37,6 +47,11 @@ static void __iomem *realtek_ictl_base;
>  #define IRR_OFFSET(idx)		(4 * (3 - (idx * 4) / 32))
>  #define IRR_SHIFT(idx)		((idx * 4) % 32)
>  
> +static inline u32 read_irr(void __iomem *irr0, int idx)

You can drop the inline. The compiler is brave enough to try that itself.

> +{
> +	return (readl(irr0 + IRR_OFFSET(idx)) >> IRR_SHIFT(idx)) & 0xf;
> +}
> +
>  static inline void write_irr(void __iomem *irr0, int idx, u32 value)
>  {
>  	unsigned int offset = IRR_OFFSET(idx);
> @@ -84,51 +99,128 @@ static struct irq_chip realtek_ictl_irq = {
>  
>  static int intc_map(struct irq_domain *d, unsigned int irq, irq_hw_number_t hw)
>  {
> +	struct realtek_ictl_output *output = d->host_data;
>  	unsigned long flags;
> +	u32 routing_old;
> +	int err = 0;
> +
> +	raw_spin_lock_irqsave(&irq_lock, flags);
> +
> +	/*
> +	 * Inputs can only be routed to one output, so they shouldn't end up in
> +	 * multiple domains. Perform this check in the same atomic context as
> +	 * configuring the routing to prevent races.
> +	 */
> +	routing_old = read_irr(REG(RTL_ICTL_IRR0), hw);
> +	if (routing_old && output->output_index != routing_old - 1) {
> +		pr_err("int %ld already routed to output %d\n",
> +			hw, routing_old - 1);
> +		err = -EINVAL;
> +		goto out;
> +	}
> +
> +	output->child_mask |= BIT(hw);
> +	write_irr(REG(RTL_ICTL_IRR0), hw, output->output_index + 1);
>  
>  	irq_set_chip_and_handler(irq, &realtek_ictl_irq, handle_level_irq);
>  
> -	raw_spin_lock_irqsave(&irq_lock, flags);
> -	write_irr(REG(RTL_ICTL_IRR0), hw, 1);
> +out:
>  	raw_spin_unlock_irqrestore(&irq_lock, flags);
>  
> -	return 0;
> +	return err;
> +}
> +
> +static int intc_select(struct irq_domain *d, struct irq_fwspec *fwspec,
> +	enum irq_domain_bus_token bus_token)
> +{
> +	struct realtek_ictl_output *output = d->host_data;
> +
> +	if (fwspec->fwnode != output->fwnode)
> +		return false;
> +
> +	/* Original specifiers only had one parameter */
> +	if (WARN_ON_ONCE(fwspec->param_count < 2))
> +		return true;

You already warned when booting and finding the old binding. Doing it
again probably is superfluous.

> +
> +	return fwspec->param[1] == output->output_index;
>  }
>  
>  static const struct irq_domain_ops irq_domain_ops = {
>  	.map = intc_map,
> +	.select = intc_select,
>  	.xlate = irq_domain_xlate_onecell,
>  };
>  
>  static void realtek_irq_dispatch(struct irq_desc *desc)
>  {
> +	struct realtek_ictl_output *output = irq_desc_get_handler_data(desc);
>  	struct irq_chip *chip = irq_desc_get_chip(desc);
> -	struct irq_domain *domain;
>  	unsigned long pending;
>  	unsigned int soc_int;
>  
>  	chained_irq_enter(chip, desc);
> -	pending = readl(REG(RTL_ICTL_GIMR)) & readl(REG(RTL_ICTL_GISR));
> +	pending = readl(REG(RTL_ICTL_GIMR)) & readl(REG(RTL_ICTL_GISR))
> +		& output->child_mask;
>  
>  	if (unlikely(!pending)) {
>  		spurious_interrupt();
>  		goto out;
>  	}
>  
> -	domain = irq_desc_get_handler_data(desc);
> -	for_each_set_bit(soc_int, &pending, 32)
> -		generic_handle_domain_irq(domain, soc_int);
> +	for_each_set_bit(soc_int, &pending, RTL_ICTL_NUM_INPUTS)
> +		generic_handle_domain_irq(output->domain, soc_int);
>  
>  out:
>  	chained_irq_exit(chip, desc);
>  }
>  
> +static int __init setup_parent_interrupts(struct device_node *node, int *parents,
> +	unsigned int num_parents)
> +{
> +	struct realtek_ictl_output *outputs;
> +	struct realtek_ictl_output *output;
> +	struct irq_domain *domain;
> +	unsigned int p;
> +
> +	outputs = kcalloc(num_parents, sizeof(*outputs), GFP_KERNEL);
> +	if (!outputs)
> +		return -ENOMEM;
> +
> +	for (p = 0; p < num_parents; p++) {
> +		output = outputs + p;
> +
> +		domain = irq_domain_add_simple(node, RTL_ICTL_NUM_INPUTS, 0,
> +					       &irq_domain_ops, output);

Consider using irq_domain_add_linear() instead. add_simple really is
legacy compatibility cruft.

> +		if (!domain)
> +			goto domain_err;
> +
> +		output->fwnode = of_node_to_fwnode(node);
> +		output->output_index = p;
> +		output->domain = domain;
> +
> +		irq_set_chained_handler_and_data(parents[p], realtek_irq_dispatch, output);
> +	}
> +
> +	return 0;
> +
> +domain_err:
> +	while (p--) {
> +		irq_set_chained_handler_and_data(parents[p], NULL, NULL);
> +		irq_domain_remove(outputs[p].domain);
> +	}
> +
> +	kfree(outputs);
> +
> +	return -ENOMEM;
> +}
> +
>  static int __init realtek_rtl_of_init(struct device_node *node, struct device_node *parent)
>  {
> +	int parent_irqs[RTL_ICTL_NUM_OUTPUTS];
>  	struct of_phandle_args oirq;
> -	struct irq_domain *domain;
> +	unsigned int num_parents;
>  	unsigned int soc_irq;
> -	int parent_irq;
> +	unsigned int p;
>  
>  	realtek_ictl_base = of_iomap(node, 0);
>  	if (!realtek_ictl_base)
> @@ -139,37 +231,43 @@ static int __init realtek_rtl_of_init(struct device_node *node, struct device_no
>  	for (soc_irq = 0; soc_irq < RTL_ICTL_NUM_INPUTS; soc_irq++)
>  		write_irr(REG(RTL_ICTL_IRR0), soc_irq, 0);
>  
> -	if (WARN_ON(!of_irq_count(node))) {
> +	num_parents = of_irq_count(node);
> +	if (num_parents > RTL_ICTL_NUM_OUTPUTS) {
> +		pr_err("too many parent interrupts\n");
> +		return -EINVAL;
> +	}
> +
> +	for (p = 0; p < num_parents; p++)
> +		parent_irqs[p] = of_irq_get(node, p);
> +
> +	if (WARN_ON(!num_parents)) {
>  		/*
>  		 * If DT contains no parent interrupts, assume MIPS CPU IRQ 2
>  		 * (HW0) is connected to the first output. This is the case for
>  		 * all known hardware anyway. "interrupt-map" is deprecated, so
>  		 * don't bother trying to parse that.
> +		 * Since this is to account for old devicetrees with one-cell
> +		 * interrupt specifiers, only one output domain is needed.
>  		 */
>  		oirq.np = of_find_compatible_node(NULL, NULL, "mti,cpu-interrupt-controller");
>  		oirq.args_count = 1;
>  		oirq.args[0] = 2;
>  
> -		parent_irq = irq_create_of_mapping(&oirq);
> +		parent_irqs[0] = irq_create_of_mapping(&oirq);
> +		num_parents = 1;
>  
>  		of_node_put(oirq.np);
> -	} else {
> -		parent_irq = of_irq_get(node, 0);
>  	}
>  
> -	if (parent_irq < 0)
> -		return parent_irq;
> -	else if (!parent_irq)
> -		return -ENODEV;
> -
> -	domain = irq_domain_add_simple(node, RTL_ICTL_NUM_INPUTS, 0,
> -				       &irq_domain_ops, NULL);
> -	if (!domain)
> -		return -ENOMEM;
> -
> -	irq_set_chained_handler_and_data(parent_irq, realtek_irq_dispatch, domain);
> +	/* Ensure we haven't collected any errors before proceeding */
> +	for (p = 0; p < num_parents; p++) {
> +		if (parent_irqs[p] < 0)
> +			return parent_irqs[p];
> +		if (!parent_irqs[p])
> +			return -ENODEV;
> +	}
>  
> -	return 0;
> +	return setup_parent_interrupts(node, &parent_irqs[0], num_parents);

Directly use 'parent' instead of &parent[0].

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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