linux-kernel - [PATCH] irqchip/sifive-plic: use hartid as context

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Message-Id: <20251020-fix-plic-amp-v1-1-defe2a99ab80@linux.dev>
Date: Mon, 20 Oct 2025 11:49:45 +0800
From: Troy Mitchell <troy.mitchell@...ux.dev>
To: Thomas Gleixner <tglx@...utronix.de>, Paul Walmsley <pjw@...nel.org>, 
 Samuel Holland <samuel.holland@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Alexandre Ghiti <alex@...ti.fr>
Cc: linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, 
 Troy Mitchell <troy.mitchell@...ux.dev>
Subject: [PATCH] irqchip/sifive-plic: use hartid as context_id in OF to fix
 AMP conflicts

In asymmetric multi-processing (AMP) scenarios, the original PLIC
driver used the context loop index 'i' as context_id for OF (device
tree) platforms. This caused multiple contexts from different harts
(e.g., core0 and core4) to share the same enable_base, leading to
conflicts when initializing the PLIC.

This patch resolves enable_base conflicts on AMP platforms while
maintaining SMP/UP behavior.

Signed-off-by: Troy Mitchell <troy.mitchell@...ux.dev>
---
 drivers/irqchip/irq-sifive-plic.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index cbd7697bc14819cbe3b77096b26901b605491f75..79867afcd321e42ad837adb5c15d0e1dc9e0e1b4 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -487,18 +487,18 @@ static int plic_parse_nr_irqs_and_contexts(struct fwnode_handle *fwnode,
 }
 
 static int plic_parse_context_parent(struct fwnode_handle *fwnode, u32 context,
-				     u32 *parent_hwirq, int *parent_cpu, u32 id)
+				     u32 *parent_hwirq, int *parent_cpu, u32 id,
+				     unsigned long *hartid)
 {
 	struct of_phandle_args parent;
-	unsigned long hartid;
 	int rc;
 
 	if (!is_of_node(fwnode)) {
-		hartid = acpi_rintc_ext_parent_to_hartid(id, context);
-		if (hartid == INVALID_HARTID)
+		*hartid = acpi_rintc_ext_parent_to_hartid(id, context);
+		if (*hartid == INVALID_HARTID)
 			return -EINVAL;
 
-		*parent_cpu = riscv_hartid_to_cpuid(hartid);
+		*parent_cpu = riscv_hartid_to_cpuid(*hartid);
 		*parent_hwirq = RV_IRQ_EXT;
 		return 0;
 	}
@@ -507,19 +507,19 @@ static int plic_parse_context_parent(struct fwnode_handle *fwnode, u32 context,
 	if (rc)
 		return rc;
 
-	rc = riscv_of_parent_hartid(parent.np, &hartid);
+	rc = riscv_of_parent_hartid(parent.np, hartid);
 	if (rc)
 		return rc;
 
 	*parent_hwirq = parent.args[0];
-	*parent_cpu = riscv_hartid_to_cpuid(hartid);
+	*parent_cpu = riscv_hartid_to_cpuid(*hartid);
 	return 0;
 }
 
 static int plic_probe(struct fwnode_handle *fwnode)
 {
 	int error = 0, nr_contexts, nr_handlers = 0, cpu, i;
-	unsigned long plic_quirks = 0;
+	unsigned long plic_quirks = 0, hartid;
 	struct plic_handler *handler;
 	u32 nr_irqs, parent_hwirq;
 	struct plic_priv *priv;
@@ -569,14 +569,14 @@ static int plic_probe(struct fwnode_handle *fwnode)
 
 	for (i = 0; i < nr_contexts; i++) {
 		error = plic_parse_context_parent(fwnode, i, &parent_hwirq, &cpu,
-						  priv->acpi_plic_id);
+						  priv->acpi_plic_id, &hartid);
 		if (error) {
 			pr_warn("%pfwP: hwirq for context%d not found\n", fwnode, i);
 			continue;
 		}
 
 		if (is_of_node(fwnode)) {
-			context_id = i;
+			context_id = hartid * 2 + i % 2;
 		} else {
 			context_id = acpi_rintc_get_plic_context(priv->acpi_plic_id, i);
 			if (context_id == INVALID_CONTEXT) {
@@ -694,7 +694,8 @@ static int plic_probe(struct fwnode_handle *fwnode)
 
 fail_cleanup_contexts:
 	for (i = 0; i < nr_contexts; i++) {
-		if (plic_parse_context_parent(fwnode, i, &parent_hwirq, &cpu, priv->acpi_plic_id))
+		if (plic_parse_context_parent(fwnode, i, &parent_hwirq, &cpu,
+					      priv->acpi_plic_id, &hartid))
 			continue;
 		if (parent_hwirq != RV_IRQ_EXT || cpu < 0)
 			continue;

---
base-commit: fdbc36b17e9f2fa24c940959e39df90f53ccce2b
change-id: 20251020-fix-plic-amp-72bd94969ca4

Best regards,
-- 
Troy Mitchell <troy.mitchell@...ux.dev>