[PATCH V2 2/2] irqchip/sifive-plic: Add thead,c9xx-plic support

guoren at kernel.org guoren at kernel.org
Tue Oct 12 08:34:32 PDT 2021

From: Guo Ren <guoren at linux.alibaba.com>

thead,c9xx-plic would mask IRQ with readl(claim), so it needn't
mask/unmask which needed in RISC-V PLIC.

When in IRQS_ONESHOT & IRQCHIP_EOI_THREADED path, unnecessary mask
operation would cause a blocking irq bug in thead,c9xx-plic. Because
when IRQ is disabled in c9xx, writel(hwirq, claim) would be invalid.

Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
Cc: Anup Patel <anup at brainfault.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Palmer Dabbelt <palmer at dabbelt.com>
Cc: Atish Patra <atish.patra at wdc.com>


Changes since V2:
 - Add a separate compatible string "thead,c9xx-plic"
 - set irq_mask/unmask of "plic_chip" to NULL and point
   irq_enable/disable of "plic_chip" to plic_irq_mask/unmask
 - Add a detailed comment block in plic_init() about the
   differences in Claim/Completion process of RISC-V PLIC and C9xx
 drivers/irqchip/irq-sifive-plic.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index cf74cfa82045..3756b1c147c3 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -79,6 +79,7 @@ struct plic_handler {
 static int plic_parent_irq __ro_after_init;
 static bool plic_cpuhp_setup_done __ro_after_init;
+static bool disable_mask_unmask __ro_after_init;
 static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
 static inline void plic_toggle(struct plic_handler *handler,
@@ -181,6 +182,13 @@ static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq,
 	struct plic_priv *priv = d->host_data;
+	if (disable_mask_unmask) {
+		plic_chip.irq_mask	= NULL;
+		plic_chip.irq_unmask	= NULL;
+		plic_chip.irq_enable	= plic_irq_unmask;
+		plic_chip.irq_disable	= plic_irq_mask;
+	}
 	irq_domain_set_info(d, irq, hwirq, &plic_chip, d->host_data,
 			    handle_fasteoi_irq, NULL, NULL);
@@ -390,5 +398,14 @@ static int __init plic_init(struct device_node *node,
 	return error;
+static int __init thead_c9xx_plic_init(struct device_node *node,
+		struct device_node *parent)
+	disable_mask_unmask = true;
+	return plic_init(node, parent);
 IRQCHIP_DECLARE(sifive_plic, "sifive,plic-1.0.0", plic_init);
 IRQCHIP_DECLARE(riscv_plic0, "riscv,plic0", plic_init); /* for legacy systems */
+IRQCHIP_DECLARE(thead_c9xx_plic, "thead,c9xx-plic", thead_c9xx_plic_init);

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