linux-kernel - [PATCH v2 6/8] genirq: soft_moderation: helpers for per-driver defaults

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Message-ID: <20251116182839.939139-7-lrizzo@google.com>
Date: Sun, 16 Nov 2025 18:28:37 +0000
From: Luigi Rizzo <lrizzo@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Marc Zyngier <maz@...nel.org>, 
	Luigi Rizzo <rizzo.unipi@...il.com>, Paolo Abeni <pabeni@...hat.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Sean Christopherson <seanjc@...gle.com>, 
	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Willem de Bruijn <willemb@...gle.com>, 
	Luigi Rizzo <lrizzo@...gle.com>
Subject: [PATCH v2 6/8] genirq: soft_moderation: helpers for per-driver defaults

Introduce helpers to implement per-driver module parameters to enable
moderation at boot/probe time.

No functional change.

Change-Id: I305aa42fa348055004cc2221ef6b055a0ab4b9d5
Signed-off-by: Luigi Rizzo <lrizzo@...gle.com>
---
 include/linux/interrupt.h   | 19 +++++++++++++++++++
 kernel/irq/irq_moderation.c | 14 ++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 51b6484c04934..17ce0aac181de 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -872,6 +872,25 @@ extern int early_irq_init(void);
 extern int arch_probe_nr_irqs(void);
 extern int arch_early_irq_init(void);
 
+#ifdef CONFIG_IRQ_SOFT_MODERATION
+
+/* helpers for per-driver moderation mode settings */
+#define DEFINE_IRQ_MODERATION_MODE_PARAMETER		\
+	static bool soft_moderation;			\
+	module_param(soft_moderation, bool, 0644);	\
+	MODULE_PARM_DESC(soft_moderation, "0: off, 1: on")
+
+void irq_moderation_set_mode(int irq, bool enable);
+#define IRQ_MODERATION_SET_DEFAULT_MODE(_irq)		\
+	irq_moderation_set_mode(_irq, READ_ONCE(soft_moderation))
+
+#else   /* empty stubs to avoid conditional compilation */
+
+#define DEFINE_IRQ_MODERATION_MODE_PARAMETER
+#define IRQ_MODERATION_SET_DEFAULT_MODE(_irq)
+
+#endif
+
 /*
  * We want to know which function is an entrypoint of a hardirq or a softirq.
  */
diff --git a/kernel/irq/irq_moderation.c b/kernel/irq/irq_moderation.c
index 2d01e4cd4638b..c2542c92fbbd5 100644
--- a/kernel/irq/irq_moderation.c
+++ b/kernel/irq/irq_moderation.c
@@ -84,6 +84,10 @@ static inline bool posted_msi_supported(void) { return false; }
  *
  *    echo "on" > /proc/irq/NN/soft_moderation # use "off" to disable
  *
+ * For selected drivers, the default can also be supplied via module parameters
+ *
+ *	${DRIVER}.soft_moderation=1
+ *
  * === MONITORING ===
  *
  * cat /proc/irq/soft_moderation shows per-CPU and global statistics.
@@ -307,6 +311,16 @@ static inline int set_moderation_mode(struct irq_desc *desc, bool enable)
 	return 0;
 }
 
+/* irq_to_desc() is not exported. Wrap it for use in drivers. */
+void irq_moderation_set_mode(int irq, bool enable)
+{
+	struct irq_desc *desc = irq_to_desc(irq);
+
+	if (desc)
+		set_moderation_mode(desc, enable);
+}
+EXPORT_SYMBOL(irq_moderation_set_mode);
+
 #pragma clang diagnostic error "-Wformat"
 /* Print statistics */
 static int moderation_show(struct seq_file *p, void *v)
-- 
2.52.0.rc1.455.g30608eb744-goog