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From: Florian Fainelli <florian.fainelli@broadcom.com>
To: linux-kernel@vger.kernel.org
Cc: Florian Fainelli <florian.fainelli@broadcom.com>,
	Tim Ross <tim.ross@broadcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-mips@vger.kernel.org (open list:BROADCOM BMIPS MIPS ARCHITECTURE),
	linux-arm-kernel@lists.infradead.org (moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE)
Subject: [PATCH v2] irqchip/irq-brcmstb-l2: Avoid saving mask on shutdown
Date: Wed, 24 Apr 2024 10:57:32 -0700
Message-Id: <20240424175732.1526531-1-florian.fainelli@broadcom.com>
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The interrupt controller shutdown path does not need to save the mask of
enabled interrupts because the next state the system is going to be in
is akin to a cold boot, or a kexec'd kernel. Saving the mask only makes
sense if the software state needs to preserve the hardware state across
a system suspend/resume cycle.

As an optimization, and given that there are systems with dozens of such
interrupt controller, we can save a "slow" memory mapped I/O read in the
shutdown path where no saving/restoring is required.

Reported-by: Tim Ross <tim.ross@broadcom.com>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
---

Changes in v2:

- expand the commit message to explain this is an optimiation saving a
  slow MMIO read

 drivers/irqchip/irq-brcmstb-l2.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/irqchip/irq-brcmstb-l2.c b/drivers/irqchip/irq-brcmstb-l2.c
index 2b0b3175cea0..c988886917f7 100644
--- a/drivers/irqchip/irq-brcmstb-l2.c
+++ b/drivers/irqchip/irq-brcmstb-l2.c
@@ -118,7 +118,7 @@ static void brcmstb_l2_intc_irq_handle(struct irq_desc *desc)
 	chained_irq_exit(chip, desc);
 }
 
-static void brcmstb_l2_intc_suspend(struct irq_data *d)
+static void __brcmstb_l2_intc_suspend(struct irq_data *d, bool save)
 {
 	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
 	struct irq_chip_type *ct = irq_data_get_chip_type(d);
@@ -127,7 +127,8 @@ static void brcmstb_l2_intc_suspend(struct irq_data *d)
 
 	irq_gc_lock_irqsave(gc, flags);
 	/* Save the current mask */
-	b->saved_mask = irq_reg_readl(gc, ct->regs.mask);
+	if (save)
+		b->saved_mask = irq_reg_readl(gc, ct->regs.mask);
 
 	if (b->can_wake) {
 		/* Program the wakeup mask */
@@ -137,6 +138,16 @@ static void brcmstb_l2_intc_suspend(struct irq_data *d)
 	irq_gc_unlock_irqrestore(gc, flags);
 }
 
+static void brcmstb_l2_intc_shutdown(struct irq_data *d)
+{
+	__brcmstb_l2_intc_suspend(d, false);
+}
+
+static void brcmstb_l2_intc_suspend(struct irq_data *d)
+{
+	__brcmstb_l2_intc_suspend(d, true);
+}
+
 static void brcmstb_l2_intc_resume(struct irq_data *d)
 {
 	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
@@ -252,7 +263,7 @@ static int __init brcmstb_l2_intc_of_init(struct device_node *np,
 
 	ct->chip.irq_suspend = brcmstb_l2_intc_suspend;
 	ct->chip.irq_resume = brcmstb_l2_intc_resume;
-	ct->chip.irq_pm_shutdown = brcmstb_l2_intc_suspend;
+	ct->chip.irq_pm_shutdown = brcmstb_l2_intc_shutdown;
 
 	if (data->can_wake) {
 		/* This IRQ chip can wake the system, set all child interrupts
-- 
2.34.1