[PATCH v2 1/5] irqchip: add dumb demultiplexer implementation

From: Boris Brezillon
Date: Tue Jan 13 2015 - 13:48:36 EST

Some interrupt controllers are multiplexing several peripheral IRQs on
a single interrupt line.
While this is not a problem for most IRQs (as long as all peripherals
request the interrupt with IRQF_SHARED flag set), multiplexing timers and
other type of peripherals will generate a WARNING (mixing IRQF_NO_SUSPEND
and !IRQF_NO_SUSPEND is prohibited).

Create a dumb irq demultiplexer which simply forwards interrupts to all
peripherals (exactly what's happening with IRQ_SHARED) but keep a unique
irq number for each peripheral, thus preventing the IRQF_NO_SUSPEND
and !IRQF_NO_SUSPEND mix on a given interrupt.

Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>
---
drivers/irqchip/Kconfig | 4 ++
drivers/irqchip/Makefile | 1 +
drivers/irqchip/irq-dumb-demux.c | 70 ++++++++++++++++++++
include/linux/irq.h | 49 ++++++++++++++
include/linux/irqdomain.h | 1 +
kernel/irq/Kconfig | 5 ++
kernel/irq/Makefile | 1 +
kernel/irq/chip.c | 41 ++++++++++++
kernel/irq/dumb-demux-chip.c | 140 +++++++++++++++++++++++++++++++++++++++
kernel/irq/handle.c | 31 ++++++++-
kernel/irq/internals.h | 3 +
11 files changed, 344 insertions(+), 2 deletions(-)
create mode 100644 drivers/irqchip/irq-dumb-demux.c
create mode 100644 kernel/irq/dumb-demux-chip.c

diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index cc79d2a..8a9df88 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -70,6 +70,10 @@ config BRCMSTB_L2_IRQ
select GENERIC_IRQ_CHIP
select IRQ_DOMAIN

+config DUMB_DEMUX_IRQ
+ bool
+ select DUMB_IRQ_DEMUX_CHIP
+
config DW_APB_ICTL
bool
select GENERIC_IRQ_CHIP
diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
index 9516a32..77f3c51 100644
--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_ARCH_MVEBU) += irq-armada-370-xp.o
obj-$(CONFIG_ARCH_MXS) += irq-mxs.o
obj-$(CONFIG_ARCH_S3C24XX) += irq-s3c24xx.o
obj-$(CONFIG_DW_APB_ICTL) += irq-dw-apb-ictl.o
+obj-$(CONFIG_DUMB_DEMUX_IRQ) += irq-dumb-demux.o
obj-$(CONFIG_METAG) += irq-metag-ext.o
obj-$(CONFIG_METAG_PERFCOUNTER_IRQS) += irq-metag.o
obj-$(CONFIG_ARCH_MOXART) += irq-moxart.o
diff --git a/drivers/irqchip/irq-dumb-demux.c b/drivers/irqchip/irq-dumb-demux.c
new file mode 100644
index 0000000..dfa05ce
--- /dev/null
+++ b/drivers/irqchip/irq-dumb-demux.c
@@ -0,0 +1,70 @@
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
+#include <linux/of_irq.h>
+#include <linux/slab.h>
+
+#include "irqchip.h"
+
+static int __init dumb_irq_demux_of_init(struct device_node *node,
+ struct device_node *parent)
+{
+ struct irq_chip_dumb_demux *demux;
+ unsigned int irq;
+ u32 valid_irqs;
+ int ret;
+
+ irq = irq_of_parse_and_map(node, 0);
+ if (!irq) {
+ pr_err("Failed to retrieve dumb irq demuxer source\n");
+ return -EINVAL;
+ }
+
+ ret = of_property_read_u32(node, "irqs", &valid_irqs);
+ if (ret) {
+ pr_err("Invalid of missing 'irqs' property\n");
+ return ret;
+ }
+
+ demux = irq_alloc_dumb_demux_chip(irq, valid_irqs,
+ IRQ_NOREQUEST | IRQ_NOPROBE |
+ IRQ_NOAUTOEN, 0, 0);
+ if (!demux) {
+ pr_err("Failed to allocate dumb irq demuxer struct\n");
+ return -ENOMEM;
+ }
+
+ demux->domain = irq_domain_add_linear(node, BITS_PER_LONG,
+ &irq_dumb_demux_domain_ops,
+ demux);
+ if (!demux->domain) {
+ ret = -ENOMEM;
+ goto err_free_demux;
+ }
+
+ ret = irq_set_handler_data(irq, demux);
+ if (ret) {
+ pr_err("Failed to assign handler data\n");
+ goto err_free_domain;
+ }
+
+ irq_set_chained_handler(irq, irq_dumb_demux_handler);
+
+ /*
+ * Disable the src irq (automatically enabled by
+ * irq_set_chained_handler) to prevent irqs from happening while
+ * nobody requested any of the demuxed irqs.
+ */
+ disable_irq(irq);
+
+ return 0;
+
+err_free_domain:
+ irq_domain_remove(demux->domain);
+
+err_free_demux:
+ kfree(demux);
+
+ return ret;
+}
+IRQCHIP_DECLARE(dumb_irq_demux, "irqchip-dumb-demux", dumb_irq_demux_of_init);
diff --git a/include/linux/irq.h b/include/linux/irq.h
index d09ec7a..ae8fa21 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -445,6 +445,10 @@ extern void handle_fasteoi_irq(unsigned int irq, struct irq_desc *desc);
extern void handle_edge_irq(unsigned int irq, struct irq_desc *desc);
extern void handle_edge_eoi_irq(unsigned int irq, struct irq_desc *desc);
extern void handle_simple_irq(unsigned int irq, struct irq_desc *desc);
+#ifdef CONFIG_DUMB_IRQ_DEMUX_CHIP
+extern irqreturn_t handle_dumb_demux_irq(unsigned int irq,
+ struct irq_desc *desc);
+#endif
extern void handle_percpu_irq(unsigned int irq, struct irq_desc *desc);
extern void handle_percpu_devid_irq(unsigned int irq, struct irq_desc *desc);
extern void handle_bad_irq(unsigned int irq, struct irq_desc *desc);
@@ -862,4 +866,49 @@ static inline u32 irq_reg_readl(struct irq_chip_generic *gc,
return readl(gc->reg_base + reg_offset);
}

+/**
+ * enum irq_dumb_demux_flags - Initialization flags for generic irq chips
+ * @IRQ_DD_INIT_NESTED_LOCK: Set the lock class of the irqs to nested for
+ * irq chips which need to call irq_set_wake() on
+ * the parent irq. Usually GPIO implementations
+ */
+enum irq_dumb_demux_flags {
+ IRQ_DD_INIT_NESTED_LOCK = 1 << 0,
+};
+
+#ifdef CONFIG_DUMB_IRQ_DEMUX_CHIP
+/**
+ * struct irq_chip_dumb_demux - Dumb demultiplexer irq chip data structure
+ * @domain: irq domain pointer
+ * @available: Bitfield of valid irqs
+ * @unmasked: Bitfield containing irqs status
+ * @flags: irq_dumb_demux_flags flags
+ * @src_irq: irq feeding the dumb demux chip
+ *
+ * Note, that irq_chip_generic can have multiple irq_chip_type
+ * implementations which can be associated to a particular irq line of
+ * an irq_chip_generic instance. That allows to share and protect
+ * state in an irq_chip_generic instance when we need to implement
+ * different flow mechanisms (level/edge) for it.
+ */
+struct irq_chip_dumb_demux {
+ struct irq_domain *domain;
+ unsigned long available;
+ unsigned long unmasked;
+ unsigned int flags;
+ unsigned int src_irq;
+ unsigned int irq_flags_to_clear;
+ unsigned int irq_flags_to_set;
+};
+
+void irq_dumb_demux_handler(unsigned int irq, struct irq_desc *desc);
+
+struct irq_chip_dumb_demux *
+irq_alloc_dumb_demux_chip(unsigned int src_irq,
+ unsigned long valid_irqs,
+ unsigned int clr_flags,
+ unsigned int set_flags,
+ unsigned int dd_flags);
+#endif /* CONFIG_DUMB_IRQ_DEMUX_CHIP */
+
#endif /* _LINUX_IRQ_H */
diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 676d730..1de3808 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -80,6 +80,7 @@ struct irq_domain_ops {
};

extern struct irq_domain_ops irq_generic_chip_ops;
+extern struct irq_domain_ops irq_dumb_demux_domain_ops;

struct irq_domain_chip_generic;

diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
index 9a76e3b..d01554a 100644
--- a/kernel/irq/Kconfig
+++ b/kernel/irq/Kconfig
@@ -51,6 +51,11 @@ config GENERIC_IRQ_CHIP
bool
select IRQ_DOMAIN

+# Dumb interrupt demuxer chip implementation
+config DUMB_IRQ_DEMUX_CHIP
+ bool
+ select IRQ_DOMAIN
+
# Generic irq_domain hw <--> linux irq number translation
config IRQ_DOMAIN
bool
diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile
index d121235..1cd4e42 100644
--- a/kernel/irq/Makefile
+++ b/kernel/irq/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_PROC_FS) += proc.o
obj-$(CONFIG_GENERIC_PENDING_IRQ) += migration.o
obj-$(CONFIG_PM_SLEEP) += pm.o
obj-$(CONFIG_GENERIC_MSI_IRQ) += msi.o
+obj-$(CONFIG_DUMB_IRQ_DEMUX_CHIP) += dumb-demux-chip.o
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 6f1c7a5..d2a5c96 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -405,6 +405,47 @@ out_unlock:
}
EXPORT_SYMBOL_GPL(handle_simple_irq);

+#ifdef CONFIG_DUMB_IRQ_DEMUX_CHIP
+/**
+ * handle_dumb_demux_irq - Dumb demuxer irq handle function.
+ * @irq: the interrupt number
+ * @desc: the interrupt description structure for this irq
+ *
+ * Dumb demux interrupts are sent from a demultiplexing interrupt handler
+ * which is not able to decide which child interrupt interrupt handler
+ * should be called.
+ *
+ * Note: The caller is expected to handle the ack, clear, mask and
+ * unmask issues if necessary.
+ */
+irqreturn_t
+handle_dumb_demux_irq(unsigned int irq, struct irq_desc *desc)
+{
+ irqreturn_t retval = IRQ_NONE;
+
+ raw_spin_lock(&desc->lock);
+
+ if (!irq_may_run(desc))
+ goto out_unlock;
+
+ desc->istate &= ~(IRQS_REPLAY | IRQS_WAITING);
+ kstat_incr_irqs_this_cpu(irq, desc);
+
+ if (unlikely(!desc->action || irqd_irq_disabled(&desc->irq_data))) {
+ desc->istate |= IRQS_PENDING;
+ goto out_unlock;
+ }
+
+ retval = handle_irq_event_no_spurious_check(desc);
+
+out_unlock:
+ raw_spin_unlock(&desc->lock);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(handle_dumb_demux_irq);
+#endif /* CONFIG_DUMB_IRQ_DEMUX_CHIP */
+
/*
* Called unconditionally from handle_level_irq() and only for oneshot
* interrupts from handle_fasteoi_irq()
diff --git a/kernel/irq/dumb-demux-chip.c b/kernel/irq/dumb-demux-chip.c
new file mode 100644
index 0000000..8e2de1d
--- /dev/null
+++ b/kernel/irq/dumb-demux-chip.c
@@ -0,0 +1,140 @@
+/*
+ * Library implementing common dumb irq demux chip functions
+ *
+ * Copyright (C) 2015, Boris Brezillon
+ */
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/interrupt.h>
+#include <linux/kernel_stat.h>
+#include <linux/syscore_ops.h>
+
+#include "internals.h"
+
+static void irq_dumb_demux_mask(struct irq_data *d)
+{
+ struct irq_chip_dumb_demux *demux = irq_data_get_irq_chip_data(d);
+
+ clear_bit(d->hwirq, &demux->unmasked);
+
+ if (!demux->unmasked)
+ disable_irq_nosync(demux->src_irq);
+}
+
+static void irq_dumb_demux_unmask(struct irq_data *d)
+{
+ struct irq_chip_dumb_demux *demux = irq_data_get_irq_chip_data(d);
+ bool enable_src_irq = !demux->unmasked;
+
+ set_bit(d->hwirq, &demux->unmasked);
+
+ if (enable_src_irq)
+ enable_irq(demux->src_irq);
+}
+
+static struct irq_chip irq_dumb_demux_chip = {
+ .name = "dumb-demux-irq",
+ .irq_mask = irq_dumb_demux_mask,
+ .irq_unmask = irq_dumb_demux_unmask,
+};
+
+/*
+ * Separate lockdep class for interrupt chip which can nest irq_desc
+ * lock.
+ */
+static struct lock_class_key irq_nested_lock_class;
+
+/*
+ * irq_map_dumb_demux_chip - Map a dumb demux chip for an irq domain
+ */
+static int irq_map_dumb_demux_chip(struct irq_domain *d,
+ unsigned int virq,
+ irq_hw_number_t hw_irq)
+{
+ struct irq_chip_dumb_demux *demux = d->host_data;
+
+ if (!test_bit(hw_irq, &demux->available))
+ return -EINVAL;
+
+ if (demux->flags & IRQ_DD_INIT_NESTED_LOCK)
+ irq_set_lockdep_class(virq, &irq_nested_lock_class);
+
+ irq_set_chip(virq, &irq_dumb_demux_chip);
+ irq_set_chip_data(virq, demux);
+ irq_modify_status(virq, demux->irq_flags_to_clear,
+ demux->irq_flags_to_set);
+
+ return 0;
+}
+
+struct irq_domain_ops irq_dumb_demux_domain_ops = {
+ .map = irq_map_dumb_demux_chip,
+ .xlate = irq_domain_xlate_onecell,
+};
+EXPORT_SYMBOL_GPL(irq_dumb_demux_domain_ops);
+
+/**
+ * irq_dumb_demux_handler - Dumb demux flow handler
+ * @irq: Virtual irq number
+ * @irq_desc: irq descriptor
+ */
+void irq_dumb_demux_handler(unsigned int irq, struct irq_desc *desc)
+{
+ struct irq_chip_dumb_demux *demux = irq_get_handler_data(irq);
+ struct irq_chip *chip = irq_desc_get_chip(desc);
+ irqreturn_t ret = IRQ_NONE;
+ int i;
+
+ chained_irq_enter(chip, desc);
+ for_each_set_bit(i, &demux->unmasked, BITS_PER_LONG) {
+ int demuxed_irq = irq_find_mapping(demux->domain, i);
+ struct irq_desc *desc = irq_to_desc(demuxed_irq);
+
+ ret |= handle_dumb_demux_irq(demuxed_irq, desc);
+ }
+ chained_irq_exit(chip, desc);
+
+ if (!noirqdebug)
+ note_interrupt(irq, desc, ret);
+}
+EXPORT_SYMBOL_GPL(irq_dumb_demux_handler);
+
+/**
+ * irq_alloc_dumb_demux_chip - Allocate a dumb demux chip
+ * @src_irq: irq feeding the dumb demux chip
+ * @dd_flags: irq_dumb_demux_flags flags
+ * @valid_irqs: Bitmask representing valid irqs
+ * @clr_flags: irq_flags to clear when mapping an interrupt
+ * @set_flags: irq_flags to set when mapping an interrupt
+ */
+struct irq_chip_dumb_demux *
+irq_alloc_dumb_demux_chip(unsigned int src_irq,
+ unsigned long valid_irqs,
+ unsigned int clr_flags,
+ unsigned int set_flags,
+ unsigned int dd_flags)
+{
+ struct irq_chip_dumb_demux *demux;
+
+ if (!src_irq)
+ return ERR_PTR(-EINVAL);
+
+ demux = kzalloc(sizeof(*demux), GFP_KERNEL);
+ if (!demux)
+ return ERR_PTR(-ENOMEM);
+
+ demux->available = valid_irqs;
+ demux->flags = dd_flags;
+ demux->src_irq = src_irq;
+ demux->irq_flags_to_clear = clr_flags;
+ demux->irq_flags_to_set = set_flags;
+
+ return demux;
+}
+EXPORT_SYMBOL_GPL(irq_alloc_dumb_demux_chip);
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 6354802..f786850 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -131,7 +131,8 @@ void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action)
}

irqreturn_t
-handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
+handle_irq_event_percpu_no_spurious_check(struct irq_desc *desc,
+ struct irqaction *action)
{
irqreturn_t retval = IRQ_NONE;
unsigned int flags = 0, irq = desc->irq_data.irq;
@@ -175,8 +176,18 @@ handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)

add_interrupt_randomness(irq, flags);

+ return retval;
+}
+
+irqreturn_t
+handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
+{
+ irqreturn_t retval;
+
+ retval = handle_irq_event_percpu_no_spurious_check(desc, action);
+
if (!noirqdebug)
- note_interrupt(irq, desc, retval);
+ note_interrupt(desc->irq_data.irq, desc, retval);
return retval;
}

@@ -195,3 +206,19 @@ irqreturn_t handle_irq_event(struct irq_desc *desc)
irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
return ret;
}
+
+irqreturn_t handle_irq_event_no_spurious_check(struct irq_desc *desc)
+{
+ struct irqaction *action = desc->action;
+ irqreturn_t ret;
+
+ desc->istate &= ~IRQS_PENDING;
+ irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS);
+ raw_spin_unlock(&desc->lock);
+
+ ret = handle_irq_event_percpu_no_spurious_check(desc, action);
+
+ raw_spin_lock(&desc->lock);
+ irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
+ return ret;
+}
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index df553b0..fe056fb 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -90,6 +90,9 @@ extern void init_kstat_irqs(struct irq_desc *desc, int node, int nr);

irqreturn_t handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action);
irqreturn_t handle_irq_event(struct irq_desc *desc);
+irqreturn_t handle_irq_event_percpu_no_spurious_check(struct irq_desc *desc,
+ struct irqaction *action);
+irqreturn_t handle_irq_event_no_spurious_check(struct irq_desc *desc);

/* Resending of interrupts :*/
void check_irq_resend(struct irq_desc *desc, unsigned int irq);
--
1.9.1

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