[PATCH v3 03/11] irqchip: mips-gic: Introduce for_each_online_cpu_gic()

[Aleksandar Rikalo]

From: Paul Burton <paulburton@xxxxxxxxxx>

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 for_each_online_cpu_gic() 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@xxxxxxxxxx>
Signed-off-by: Chao-ying Fu <cfu@xxxxxxxxxxxx>
Signed-off-by: Dragan Mladjenovic <dragan.mladjenovic@xxxxxxxxxx>
Signed-off-by: Aleksandar Rikalo <aleksandar.rikalo@xxxxxxxxxx>
---
 drivers/irqchip/irq-mips-gic.c | 61 +++++++++++++++++++++++++++++-----
 1 file changed, 52 insertions(+), 9 deletions(-)

diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index 76253e864f23..9e7182150b5c 100644
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -66,6 +66,52 @@ 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;
+}
+
+static inline void __lockdep_assert_held(raw_spinlock_t *gic_lock)
+{
+	lockdep_assert_held(gic_lock);
+}
+
+/**
+ * for_each_online_cpu_gic() - Iterate over online CPUs, access local registers
+ * @cpu: An integer variable to hold the current CPU number
+ * @gic_lock: A pointer to raw spin lock used as a guard
+ *
+ * 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 for_each_online_cpu_gic(cpu, gic_lock)		\
+	for (__lockdep_assert_held(gic_lock),		\
+	     (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;
@@ -358,10 +404,9 @@ static void gic_mask_local_irq_all_vpes(struct irq_data *d)
 	cd->mask = false;
 
 	raw_spin_lock_irqsave(&gic_lock, flags);
-	for_each_online_cpu(cpu) {
-		write_gic_vl_other(mips_cm_vp_id(cpu));
+	for_each_online_cpu_gic(cpu, &gic_lock)
 		write_gic_vo_rmask(BIT(intr));
-	}
+
 	raw_spin_unlock_irqrestore(&gic_lock, flags);
 }
 
@@ -376,10 +421,9 @@ static void gic_unmask_local_irq_all_vpes(struct irq_data *d)
 	cd->mask = true;
 
 	raw_spin_lock_irqsave(&gic_lock, flags);
-	for_each_online_cpu(cpu) {
-		write_gic_vl_other(mips_cm_vp_id(cpu));
+	for_each_online_cpu_gic(cpu, &gic_lock)
 		write_gic_vo_smask(BIT(intr));
-	}
+
 	raw_spin_unlock_irqrestore(&gic_lock, flags);
 }
 
@@ -534,10 +578,9 @@ static int gic_irq_domain_map(struct irq_domain *d, unsigned int virq,
 		return -EPERM;
 
 	raw_spin_lock_irqsave(&gic_lock, flags);
-	for_each_online_cpu(cpu) {
-		write_gic_vl_other(mips_cm_vp_id(cpu));
+	for_each_online_cpu_gic(cpu, &gic_lock)
 		write_gic_vo_map(mips_gic_vx_map_reg(intr), map);
-	}
+
 	raw_spin_unlock_irqrestore(&gic_lock, flags);
 
 	return 0;
-- 
2.25.1