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SubjectRe: [PATCH] irqchip/sifive-plic: Add support for multiple PLICs
Date
From
[Fixing Palmer's email address]

On 2019-12-06 02:31, Atish Patra wrote:
> Current, PLIC driver can support only 1 PLIC on the board. However,
> there can be multiple PLICs present on a two socket systems in
> RISC-V.
>
> Modify the driver so that each PLIC handler can have a information
> about individual PLIC registers and an irqdomain associated with it.
>
> Tested on two socket RISC-V system based on VCU118 FPGA connected via
> OmniXtend protocol.
>
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> Signed-off-by: Anup Patel <anup.patel@wdc.com>

There seem to be some confusion here about who the author of the patch
is.
If this is a co-development, please use the appropriate tag.

> ---
> drivers/irqchip/irq-sifive-plic.c | 81
> +++++++++++++++++++------------
> 1 file changed, 51 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/irqchip/irq-sifive-plic.c
> b/drivers/irqchip/irq-sifive-plic.c
> index c72c036aea76..aea1f2f0f0d5 100644
> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -55,7 +55,11 @@
> #define CONTEXT_THRESHOLD 0x00
> #define CONTEXT_CLAIM 0x04
>
> -static void __iomem *plic_regs;
> +struct plic_hw {
> + struct cpumask lmask;
> + struct irq_domain *irqdomain;
> + void __iomem *regs;
> +};

The '_hw' suffix is a bit unfortunate, as there is mostly SW constructs
in this structure. Maybe something more general like 'context' would
be more appropriate.

>
> struct plic_handler {
> bool present;
> @@ -66,6 +70,7 @@ struct plic_handler {
> */
> raw_spinlock_t enable_lock;
> void __iomem *enable_base;
> + struct plic_hw *hw;
> };
> static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
>
> @@ -84,31 +89,40 @@ static inline void plic_toggle(struct
> plic_handler *handler,
> }
>
> static inline void plic_irq_toggle(const struct cpumask *mask,
> - int hwirq, int enable)
> + struct irq_data *d, int enable)
> {
> int cpu;
> + struct plic_hw *hw = d->domain->host_data;

The usual construct is to transfer the domain->host_data pointer to
the irq_data->chip_data pointer at map() time, using
irq_set_chip_data().

You can then retrieve the pointer with irq_get_chip_data(), and save
yourselves some pointer chasing.

>
> - writel(enable, plic_regs + PRIORITY_BASE + hwirq *
> PRIORITY_PER_ID);
> + writel(enable, hw->regs + PRIORITY_BASE + d->hwirq *
> PRIORITY_PER_ID);
> for_each_cpu(cpu, mask) {
> struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
>
> - if (handler->present)
> - plic_toggle(handler, hwirq, enable);
> + if (handler->present &&
> + cpumask_test_cpu(cpu, &handler->hw->lmask))
> + plic_toggle(handler, d->hwirq, enable);
> }
> }
>
> static void plic_irq_enable(struct irq_data *d)
> {
> - unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d),
> - cpu_online_mask);
> + struct cpumask amask;
> + unsigned int cpu;
> + struct plic_hw *hw = d->domain->host_data;
> +
> + cpumask_and(&amask, &hw->lmask, cpu_online_mask);
> + cpu = cpumask_any_and(irq_data_get_affinity_mask(d),
> + &amask);
> if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
> return;
> - plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1);
> + plic_irq_toggle(cpumask_of(cpu), d, 1);
> }
>
> static void plic_irq_disable(struct irq_data *d)
> {
> - plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
> + struct plic_hw *hw = d->domain->host_data;
> +
> + plic_irq_toggle(&hw->lmask, d, 0);
> }
>
> #ifdef CONFIG_SMP
> @@ -116,18 +130,22 @@ static int plic_set_affinity(struct irq_data
> *d,
> const struct cpumask *mask_val, bool force)
> {
> unsigned int cpu;
> + struct cpumask amask;
> + struct plic_hw *hw = d->domain->host_data;
> +
> + cpumask_and(&amask, &hw->lmask, mask_val);

So this means that an interrupt cannot move between sockets?
How is that going to work with CPU hotplug? This seems like
a pretty bad restriction for anything but the most basic
experimental platform.

>
> if (force)
> - cpu = cpumask_first(mask_val);
> + cpu = cpumask_first(&amask);
> else
> - cpu = cpumask_any_and(mask_val, cpu_online_mask);
> + cpu = cpumask_any_and(&amask, cpu_online_mask);
>
> if (cpu >= nr_cpu_ids)
> return -EINVAL;
>
> if (!irqd_irq_disabled(d)) {
> - plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
> - plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1);
> + plic_irq_toggle(&hw->lmask, d, 0);
> + plic_irq_toggle(cpumask_of(cpu), d, 1);
> }
>
> irq_data_update_effective_affinity(d, cpumask_of(cpu));
> @@ -163,8 +181,6 @@ static const struct irq_domain_ops
> plic_irqdomain_ops = {
> .xlate = irq_domain_xlate_onecell,
> };
>
> -static struct irq_domain *plic_irqdomain;
> -
> /*
> * Handling an interrupt is a two-step process: first you claim the
> interrupt
> * by reading the claim register, then you complete the interrupt by
> writing
> @@ -181,7 +197,7 @@ static void plic_handle_irq(struct pt_regs *regs)
>
> csr_clear(sie, SIE_SEIE);
> while ((hwirq = readl(claim))) {
> - int irq = irq_find_mapping(plic_irqdomain, hwirq);
> + int irq = irq_find_mapping(handler->hw->irqdomain, hwirq);
>
> if (unlikely(irq <= 0))
> pr_warn_ratelimited("can't find mapping for hwirq %lu\n",
> @@ -212,15 +228,17 @@ static int __init plic_init(struct device_node
> *node,
> {
> int error = 0, nr_contexts, nr_handlers = 0, i;
> u32 nr_irqs;
> + struct plic_hw *hw;
>
> - if (plic_regs) {
> - pr_warn("PLIC already present.\n");
> - return -ENXIO;
> - }
> + hw = kzalloc(sizeof(*hw), GFP_KERNEL);
> + if (!hw)
> + return -ENOMEM;
>
> - plic_regs = of_iomap(node, 0);
> - if (WARN_ON(!plic_regs))
> - return -EIO;
> + hw->regs = of_iomap(node, 0);
> + if (WARN_ON(!hw->regs)) {
> + error = -EIO;
> + goto out_freehw;
> + }
>
> error = -EINVAL;
> of_property_read_u32(node, "riscv,ndev", &nr_irqs);
> @@ -234,9 +252,9 @@ static int __init plic_init(struct device_node
> *node,
> goto out_iounmap;
>
> error = -ENOMEM;
> - plic_irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
> - &plic_irqdomain_ops, NULL);
> - if (WARN_ON(!plic_irqdomain))
> + hw->irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
> + &plic_irqdomain_ops, hw);
> + if (WARN_ON(!hw->irqdomain))
> goto out_iounmap;
>
> for (i = 0; i < nr_contexts; i++) {
> @@ -279,13 +297,14 @@ static int __init plic_init(struct device_node
> *node,
> goto done;
> }
>
> + cpumask_set_cpu(cpu, &hw->lmask);
> handler->present = true;
> handler->hart_base =
> - plic_regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
> + hw->regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
> raw_spin_lock_init(&handler->enable_lock);
> handler->enable_base =
> - plic_regs + ENABLE_BASE + i * ENABLE_PER_HART;
> -
> + hw->regs + ENABLE_BASE + i * ENABLE_PER_HART;
> + handler->hw = hw;
> done:
> /* priority must be > threshold to trigger an interrupt */
> writel(threshold, handler->hart_base + CONTEXT_THRESHOLD);
> @@ -300,7 +319,9 @@ static int __init plic_init(struct device_node
> *node,
> return 0;
>
> out_iounmap:
> - iounmap(plic_regs);
> + iounmap(hw->regs);
> +out_freehw:
> + kfree(hw);
> return error;
> }

This otherwise seems like a very straightforward change.

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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