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From:   Dragan Mladjenovic <Dragan.Mladjenovic@syrmia.com>
To:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc:     Chao-ying Fu <cfu@wavecomp.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Greg Ungerer <gerg@kernel.org>,
        Hauke Mehrtens <hauke@hauke-m.de>,
        Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,
        Marc Zyngier <maz@kernel.org>,
        Paul Burton <paulburton@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Serge Semin <fancer.lancer@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tiezhu Yang <yangtiezhu@loongson.cn>,
        Dragan Mladjenovic <dragan.mladjenovic@syrmia.com>
Subject: [PATCH v2 03/12] irqchip: mips-gic: Introduce gic_with_each_online_cpu()
Date:   Wed, 25 May 2022 14:10:21 +0200
Message-Id: <20220525121030.16054-4-Dragan.Mladjenovic@syrmia.com>
In-Reply-To: <20220525121030.16054-1-Dragan.Mladjenovic@syrmia.com>
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From: Paul Burton <paulburton@kernel.org>

A few pieces of code in the MIPS GIC driver operate on the GIC local
register block for each online CPU, accessing each via the GIC's
other/redirect register block. This patch abstracts the process of
iterating over online CPUs & configuring the other/redirect region to
access their registers through a new gic_with_each_online_cpu() macro.

This simplifies users of the new macro slightly, and more importantly
prepares us for handling multi-cluster systems where the register
configuration will be done via the CM's GCR_CL_REDIRECT register. By
abstracting all other/redirect block configuration through this macro,
and the __gic_with_next_online_cpu() function which backs it, users will
trivially gain support for multi-cluster when it is implemented in
__gic_with_next_online_cpu().

Signed-off-by: Paul Burton <paulburton@kernel.org>
Signed-off-by: Chao-ying Fu <cfu@wavecomp.com>
Signed-off-by: Dragan Mladjenovic <dragan.mladjenovic@syrmia.com>

diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index ff89b36267dd..4872bebe24cf 100644
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -65,6 +65,45 @@ static struct gic_all_vpes_chip_data {
 	bool	mask;
 } gic_all_vpes_chip_data[GIC_NUM_LOCAL_INTRS];
 
+static int __gic_with_next_online_cpu(int prev)
+{
+	unsigned int cpu;
+
+	/* Discover the next online CPU */
+	cpu = cpumask_next(prev, cpu_online_mask);
+
+	/* If there isn't one, we're done */
+	if (cpu >= nr_cpu_ids)
+		return cpu;
+
+	/*
+	 * Lock access to the next CPU's GIC local register block.
+	 *
+	 * In the single cluster case we simply set GIC_VL_OTHER. The caller
+	 * holds gic_lock so nothing can clobber the value we write.
+	 */
+	write_gic_vl_other(mips_cm_vp_id(cpu));
+
+	return cpu;
+}
+
+/**
+ * gic_with_each_online_cpu() - Iterate over online CPUs, access local registers
+ * @cpu: An integer variable to hold the current CPU number
+ *
+ * Iterate over online CPUs & configure the other/redirect register region to
+ * access each CPUs GIC local register block, which can be accessed from the
+ * loop body using read_gic_vo_*() or write_gic_vo_*() accessor functions or
+ * their derivatives.
+ *
+ * The caller must hold gic_lock throughout the loop, such that GIC_VL_OTHER
+ * cannot be clobbered.
+ */
+#define gic_with_each_online_cpu(cpu)			\
+	for ((cpu) = __gic_with_next_online_cpu(-1);	\
+	     (cpu) = __gic_with_next_online_cpu(cpu),	\
+	     (cpu) < nr_cpu_ids;)
+
 static void gic_clear_pcpu_masks(unsigned int intr)
 {
 	unsigned int i;
@@ -357,10 +396,8 @@ static void gic_mask_local_irq_all_vpes(struct irq_data *d)
 	cd->mask = false;
 
 	spin_lock_irqsave(&gic_lock, flags);
-	for_each_online_cpu(cpu) {
-		write_gic_vl_other(mips_cm_vp_id(cpu));
+	gic_with_each_online_cpu(cpu)
 		write_gic_vo_rmask(BIT(intr));
-	}
 	spin_unlock_irqrestore(&gic_lock, flags);
 }
 
@@ -375,10 +412,8 @@ static void gic_unmask_local_irq_all_vpes(struct irq_data *d)
 	cd->mask = true;
 
 	spin_lock_irqsave(&gic_lock, flags);
-	for_each_online_cpu(cpu) {
-		write_gic_vl_other(mips_cm_vp_id(cpu));
+	gic_with_each_online_cpu(cpu)
 		write_gic_vo_smask(BIT(intr));
-	}
 	spin_unlock_irqrestore(&gic_lock, flags);
 }
 
@@ -532,10 +567,8 @@ static int gic_irq_domain_map(struct irq_domain *d, unsigned int virq,
 		return -EPERM;
 
 	spin_lock_irqsave(&gic_lock, flags);
-	for_each_online_cpu(cpu) {
-		write_gic_vl_other(mips_cm_vp_id(cpu));
+	gic_with_each_online_cpu(cpu)
 		write_gic_vo_map(mips_gic_vx_map_reg(intr), map);
-	}
 	spin_unlock_irqrestore(&gic_lock, flags);
 
 	return 0;
-- 
2.17.1