Message-ID: <c028375949d104b52d16a0e1865e132bd224392f.camel@svanheule.net>
Date:   Wed, 09 Feb 2022 22:22:26 +0100
From:   Sander Vanheule <sander@...nheule.net>
To:     Marc Zyngier <maz@...nel.org>
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 Wed, 2022-02-09 at 14:10 +0000, Marc Zyngier wrote:
> 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.
> 

What would be the alternative? I would really rather not hardcode priority tables in the
driver... For what it's worth, I see that at least "arm,nvic" and "atmel,aic" have
explicit priority specifier cells.


> > 
> > 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.

I had changed this originally, but decided to stick to add_simple to avoid unrelated
changes. Unless you rather have that I roll into one of the current patches, I'll add a
small extra patch to implement this switch.

> 
> > +               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].

Will update this, the WARN_ON_ONCE, and the inline in the next revision.

Best,
Sander

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