Re: [PATCH v5 2/9] irqchip/riscv-intc: Add support for RISC-V AIA

Andrew Jones
2023-07-11T14:12:39Z

On Mon, Jul 10, 2023 at 03:13:14PM +0530, Anup Patel wrote:
> The RISC-V advanced interrupt architecture (AIA) extends the per-HART
> local interrupts in following ways:
> 1. Minimum 64 local interrupts for both RV32 and RV64
> 2. Ability to process multiple pending local interrupts in same
> interrupt handler
> 3. Priority configuration for each local interrupts
> 4. Special CSRs to configure/access the per-HART MSI controller

afaict, we're only doing (1) and (2) from this list in this patch.

>
> This patch adds support for RISC-V AIA in the RISC-V intc driver.
>
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
> drivers/irqchip/irq-riscv-intc.c | 36 ++++++++++++++++++++++++++------
> 1 file changed, 30 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
> index 4adeee1bc391..e235bf1708a4 100644
> --- a/drivers/irqchip/irq-riscv-intc.c
> +++ b/drivers/irqchip/irq-riscv-intc.c
> @@ -17,6 +17,7 @@
> #include <linux/module.h>
> #include <linux/of.h>
> #include <linux/smp.h>
> +#include <asm/hwcap.h>
>
> static struct irq_domain *intc_domain;
>
> @@ -30,6 +31,15 @@ static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
> generic_handle_domain_irq(intc_domain, cause);
> }
>
> +static asmlinkage void riscv_intc_aia_irq(struct pt_regs *regs)
> +{
> + unsigned long topi;
> +
> + while ((topi = csr_read(CSR_TOPI)))
> + generic_handle_domain_irq(intc_domain,
> + topi >> TOPI_IID_SHIFT);
> +}
> +
> /*
> * On RISC-V systems local interrupts are masked or unmasked by writing
> * the SIE (Supervisor Interrupt Enable) CSR. As CSRs can only be written
> @@ -39,12 +49,18 @@ static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
>
> static void riscv_intc_irq_mask(struct irq_data *d)
> {
> - csr_clear(CSR_IE, BIT(d->hwirq));
> + if (d->hwirq < BITS_PER_LONG)
> + csr_clear(CSR_IE, BIT(d->hwirq));
> + else
> + csr_clear(CSR_IEH, BIT(d->hwirq - BITS_PER_LONG));

We can optimize rv64 by allowing the compiler to remove the branch

if (IS_ENABLED(CONFIG_32BIT) && d->hwirq >= 32)
csr_clear(CSR_IEH, BIT(d->hwirq - 32));
else
csr_clear(CSR_IE, BIT(d->hwirq));

> }
>
> static void riscv_intc_irq_unmask(struct irq_data *d)
> {
> - csr_set(CSR_IE, BIT(d->hwirq));
> + if (d->hwirq < BITS_PER_LONG)
> + csr_set(CSR_IE, BIT(d->hwirq));
> + else
> + csr_set(CSR_IEH, BIT(d->hwirq - BITS_PER_LONG));

Same comment as above.

> }
>
> static void riscv_intc_irq_eoi(struct irq_data *d)
> @@ -115,16 +131,22 @@ static struct fwnode_handle *riscv_intc_hwnode(void)
>
> static int __init riscv_intc_init_common(struct fwnode_handle *fn)
> {
> - int rc;
> + int rc, nr_irqs = BITS_PER_LONG;
> +
> + if (riscv_isa_extension_available(NULL, SxAIA) && BITS_PER_LONG == 32)
> + nr_irqs = nr_irqs * 2;

The AIA spec states sie and sip are explicitly 64, so how about writing
this as

int rc, nr_irqs = BITS_PER_LONG;

if (riscv_isa_extension_available(NULL, SxAIA))
nr_irqs = 64;

>
> - intc_domain = irq_domain_create_linear(fn, BITS_PER_LONG,
> + intc_domain = irq_domain_create_linear(fn, nr_irqs,
> &riscv_intc_domain_ops, NULL);
> if (!intc_domain) {
> pr_err("unable to add IRQ domain\n");
> return -ENXIO;
> }
>
> - rc = set_handle_irq(&riscv_intc_irq);
> + if (riscv_isa_extension_available(NULL, SxAIA))
> + rc = set_handle_irq(&riscv_intc_aia_irq);
> + else
> + rc = set_handle_irq(&riscv_intc_irq);

nit: blank line here

> if (rc) {
> pr_err("failed to set irq handler\n");
> return rc;
> @@ -132,7 +154,9 @@ static int __init riscv_intc_init_common(struct fwnode_handle *fn)
>
> riscv_set_intc_hwnode_fn(riscv_intc_hwnode);
>
> - pr_info("%d local interrupts mapped\n", BITS_PER_LONG);
> + pr_info("%d local interrupts mapped%s\n",
> + nr_irqs, (riscv_isa_extension_available(NULL, SxAIA)) ?

nit: unnecessary ()

> + " using AIA" : "");
>
> return 0;
> }
> --
> 2.34.1
>

Thanks,
drew