linux-kernel - [RFC PATCH 2/4] irqchip/riscv-intc: Support large non-standard hwirq number

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Date:   Thu, 7 Sep 2023 10:16:33 +0800
From:   Yu Chien Peter Lin <peterlin@...estech.com>
To:     <linux-riscv@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
        <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <conor.dooley@...rochip.com>,
        <atishp@...shpatra.org>, <anup@...infault.org>,
        <prabhakar.mahadev-lad.rj@...renesas.com>
CC:     <ajones@...tanamicro.com>, <heiko@...ech.de>,
        <samuel@...lland.org>, <geert+renesas@...der.be>,
        <n.shubin@...ro.com>, <dminus@...estech.com>,
        <ycliang@...estech.com>, <tim609@...estech.com>,
        <locus84@...estech.com>, <dylan@...estech.com>,
        Yu Chien Peter Lin <peterlin@...estech.com>
Subject: [RFC PATCH 2/4] irqchip/riscv-intc: Support large non-standard hwirq number

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 cause >= 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@...estech.com>
Reviewed-by: Charles Ci-Jyun Wu <dminus@...estech.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@...estech.com>

---
There are 3 hwirqs of local interrupt source exceed 64 defined in
AX45MP datasheet [1] Table 56: AX45MP-1C scause Value After Trap:
- 256+16 Slave port ECC error interrupt (S-mode)
- 256+17 Bus write transaction error interrupt (S-mode)
- 256+18 Performance monitor overflow interrupt(S-mode)

[1] http://www.andestech.com/wp-content/uploads/AX45MP-1C-Rev.-5.0.0-Datasheet.pdf
---
 drivers/irqchip/irq-riscv-intc.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
index 4adeee1bc391..76e1229c45de 100644
--- a/drivers/irqchip/irq-riscv-intc.c
+++ b/drivers/irqchip/irq-riscv-intc.c
@@ -24,8 +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");
+	if (!irq_find_mapping(intc_domain, cause))
+		panic("unexpected interrupt cause: %ld", cause);
 
 	generic_handle_domain_irq(intc_domain, cause);
 }
@@ -117,8 +117,8 @@ 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 +132,6 @@ 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