[RFC PATCH v3 02/13] irqchip/riscv-intc: Allow large non-standard hwirq number

Yu Chien Peter Lin
2023-10-22T15:24:20Z

Currently, the implementation of the RISC-V INTC driver uses the
interrupt cause as hwirq and has a limitation of supporting a
maximum of 64 hwirqs. However, according to the privileged spec,
interrupt causes >= 16 are defined for platform use.

This limitation prevents us from fully utilizing the available
local interrupt sources. Additionally, the hwirqs used on RISC-V
are sparse, with only interrupt numbers 1, 5 and 9 (plus Sscofpmf
or T-Head's PMU irq) being currently used for supervisor mode.

The patch switches to using irq_domain_create_tree() which
creates the radix tree map, allowing us to handle a larger
number of hwirqs.

Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com>
Reviewed-by: Charles Ci-Jyun Wu <dminus@andestech.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
---
Changes v1 -> v2:
- Fixed irq mapping failure checking (suggested by Clément and Anup)
Changes v2 -> v3:
- No change
---
drivers/irqchip/irq-riscv-intc.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
index e8d01b14ccdd..79d049105384 100644
--- a/drivers/irqchip/irq-riscv-intc.c
+++ b/drivers/irqchip/irq-riscv-intc.c
@@ -24,10 +24,8 @@ static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
{
unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;

- if (unlikely(cause >= BITS_PER_LONG))
- panic("unexpected interrupt cause");
-
- generic_handle_domain_irq(intc_domain, cause);
+ if (generic_handle_domain_irq(intc_domain, cause))
+ pr_warn("Failed to handle interrupt (cause: %ld)\n", cause);
}

/*
@@ -117,8 +115,8 @@ static int __init riscv_intc_init_common(struct fwnode_handle *fn)
{
int rc;

- intc_domain = irq_domain_create_linear(fn, BITS_PER_LONG,
- &riscv_intc_domain_ops, NULL);
+ intc_domain = irq_domain_create_tree(fn, &riscv_intc_domain_ops,
+ NULL);
if (!intc_domain) {
pr_err("unable to add IRQ domain\n");
return -ENXIO;
@@ -132,8 +130,6 @@ 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);
-
return 0;
}

--
2.34.1