[tip:irq/core] irqchip: Add per-cpu interrupt partitioning library

From: tip-bot for Marc Zyngier
Date: Mon May 02 2016 - 08:35:57 EST


Commit-ID: 9e2c986cb460bf97154f18e85aa833739a1e8dc7
Gitweb: http://git.kernel.org/tip/9e2c986cb460bf97154f18e85aa833739a1e8dc7
Author: Marc Zyngier <marc.zyngier@xxxxxxx>
AuthorDate: Mon, 11 Apr 2016 09:57:53 +0100
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Mon, 2 May 2016 13:42:51 +0200

irqchip: Add per-cpu interrupt partitioning library

We've unfortunately started seeing a situation where percpu interrupts
are partitioned in the system: one arbitrary set of CPUs has an
interrupt connected to a type of device, while another disjoint
set of CPUs has the same interrupt connected to another type of device.

This makes it impossible to have a device driver requesting this interrupt
using the current percpu-interrupt abstraction, as the same interrupt number
is now potentially claimed by at least two drivers, and we forbid interrupt
sharing on per-cpu interrupt.

A solution to this is to turn things upside down. Let's assume that our
system describes all the possible partitions for a given interrupt, and
give each of them a unique identifier. It is then possible to create
a namespace where the affinity identifier itself is a form of interrupt
number. At this point, it becomes easy to implement a set of partitions
as a cascaded irqchip, each affinity identifier being the HW irq.

This allows us to keep a number of nice properties:
- Each partition results in a separate percpu-interrupt (with a restrictied
affinity), which keeps drivers happy.
- Because the underlying interrupt is still per-cpu, the overhead of
the indirection can be kept pretty minimal.
- The core code can ignore most of that crap.

For that purpose, we implement a small library that deals with some of
the boilerplate code, relying on platform-specific drivers to provide
a description of the affinity sets and a set of callbacks.

Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: devicetree@xxxxxxxxxxxxxxx
Cc: Jason Cooper <jason@xxxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Rob Herring <robh+dt@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1460365075-7316-4-git-send-email-marc.zyngier@xxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

---
drivers/irqchip/Kconfig | 3 +
drivers/irqchip/Makefile | 1 +
drivers/irqchip/irq-partition-percpu.c | 256 +++++++++++++++++++++++++++
include/linux/irqchip/irq-partition-percpu.h | 59 ++++++
4 files changed, 319 insertions(+)

diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index 3e12479..ea1836b 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -244,3 +244,6 @@ config IRQ_MXS
config MVEBU_ODMI
bool
select GENERIC_MSI_IRQ_DOMAIN
+
+config PARTITION_PERCPU
+ bool
diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
index b03cfcb..e354b00c 100644
--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_REALVIEW_DT) += irq-gic-realview.o
obj-$(CONFIG_ARM_GIC_V2M) += irq-gic-v2m.o
obj-$(CONFIG_ARM_GIC_V3) += irq-gic-v3.o irq-gic-common.o
obj-$(CONFIG_ARM_GIC_V3_ITS) += irq-gic-v3-its.o irq-gic-v3-its-pci-msi.o irq-gic-v3-its-platform-msi.o
+obj-$(CONFIG_PARTITION_PERCPU) += irq-partition-percpu.o
obj-$(CONFIG_HISILICON_IRQ_MBIGEN) += irq-mbigen.o
obj-$(CONFIG_ARM_NVIC) += irq-nvic.o
obj-$(CONFIG_ARM_VIC) += irq-vic.o
diff --git a/drivers/irqchip/irq-partition-percpu.c b/drivers/irqchip/irq-partition-percpu.c
new file mode 100644
index 0000000..ccd72c2
--- /dev/null
+++ b/drivers/irqchip/irq-partition-percpu.c
@@ -0,0 +1,256 @@
+/*
+ * Copyright (C) 2016 ARM Limited, All Rights Reserved.
+ * Author: Marc Zyngier <marc.zyngier@xxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/bitops.h>
+#include <linux/interrupt.h>
+#include <linux/irqchip.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/irqchip/irq-partition-percpu.h>
+#include <linux/irqdomain.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+
+struct partition_desc {
+ int nr_parts;
+ struct partition_affinity *parts;
+ struct irq_domain *domain;
+ struct irq_desc *chained_desc;
+ unsigned long *bitmap;
+ struct irq_domain_ops ops;
+};
+
+static bool partition_check_cpu(struct partition_desc *part,
+ unsigned int cpu, unsigned int hwirq)
+{
+ return cpumask_test_cpu(cpu, &part->parts[hwirq].mask);
+}
+
+static void partition_irq_mask(struct irq_data *d)
+{
+ struct partition_desc *part = irq_data_get_irq_chip_data(d);
+ struct irq_chip *chip = irq_desc_get_chip(part->chained_desc);
+ struct irq_data *data = irq_desc_get_irq_data(part->chained_desc);
+
+ if (partition_check_cpu(part, smp_processor_id(), d->hwirq) &&
+ chip->irq_mask)
+ chip->irq_mask(data);
+}
+
+static void partition_irq_unmask(struct irq_data *d)
+{
+ struct partition_desc *part = irq_data_get_irq_chip_data(d);
+ struct irq_chip *chip = irq_desc_get_chip(part->chained_desc);
+ struct irq_data *data = irq_desc_get_irq_data(part->chained_desc);
+
+ if (partition_check_cpu(part, smp_processor_id(), d->hwirq) &&
+ chip->irq_unmask)
+ chip->irq_unmask(data);
+}
+
+static int partition_irq_set_irqchip_state(struct irq_data *d,
+ enum irqchip_irq_state which,
+ bool val)
+{
+ struct partition_desc *part = irq_data_get_irq_chip_data(d);
+ struct irq_chip *chip = irq_desc_get_chip(part->chained_desc);
+ struct irq_data *data = irq_desc_get_irq_data(part->chained_desc);
+
+ if (partition_check_cpu(part, smp_processor_id(), d->hwirq) &&
+ chip->irq_set_irqchip_state)
+ return chip->irq_set_irqchip_state(data, which, val);
+
+ return -EINVAL;
+}
+
+static int partition_irq_get_irqchip_state(struct irq_data *d,
+ enum irqchip_irq_state which,
+ bool *val)
+{
+ struct partition_desc *part = irq_data_get_irq_chip_data(d);
+ struct irq_chip *chip = irq_desc_get_chip(part->chained_desc);
+ struct irq_data *data = irq_desc_get_irq_data(part->chained_desc);
+
+ if (partition_check_cpu(part, smp_processor_id(), d->hwirq) &&
+ chip->irq_get_irqchip_state)
+ return chip->irq_get_irqchip_state(data, which, val);
+
+ return -EINVAL;
+}
+
+static int partition_irq_set_type(struct irq_data *d, unsigned int type)
+{
+ struct partition_desc *part = irq_data_get_irq_chip_data(d);
+ struct irq_chip *chip = irq_desc_get_chip(part->chained_desc);
+ struct irq_data *data = irq_desc_get_irq_data(part->chained_desc);
+
+ if (chip->irq_set_type)
+ return chip->irq_set_type(data, type);
+
+ return -EINVAL;
+}
+
+static void partition_irq_print_chip(struct irq_data *d, struct seq_file *p)
+{
+ struct partition_desc *part = irq_data_get_irq_chip_data(d);
+ struct irq_chip *chip = irq_desc_get_chip(part->chained_desc);
+ struct irq_data *data = irq_desc_get_irq_data(part->chained_desc);
+
+ seq_printf(p, " %5s-%lu", chip->name, data->hwirq);
+}
+
+static struct irq_chip partition_irq_chip = {
+ .irq_mask = partition_irq_mask,
+ .irq_unmask = partition_irq_unmask,
+ .irq_set_type = partition_irq_set_type,
+ .irq_get_irqchip_state = partition_irq_get_irqchip_state,
+ .irq_set_irqchip_state = partition_irq_set_irqchip_state,
+ .irq_print_chip = partition_irq_print_chip,
+};
+
+static void partition_handle_irq(struct irq_desc *desc)
+{
+ struct partition_desc *part = irq_desc_get_handler_data(desc);
+ struct irq_chip *chip = irq_desc_get_chip(desc);
+ int cpu = smp_processor_id();
+ int hwirq;
+
+ chained_irq_enter(chip, desc);
+
+ for_each_set_bit(hwirq, part->bitmap, part->nr_parts) {
+ if (partition_check_cpu(part, cpu, hwirq))
+ break;
+ }
+
+ if (unlikely(hwirq == part->nr_parts)) {
+ handle_bad_irq(desc);
+ } else {
+ unsigned int irq;
+ irq = irq_find_mapping(part->domain, hwirq);
+ generic_handle_irq(irq);
+ }
+
+ chained_irq_exit(chip, desc);
+}
+
+static int partition_domain_alloc(struct irq_domain *domain, unsigned int virq,
+ unsigned int nr_irqs, void *arg)
+{
+ int ret;
+ irq_hw_number_t hwirq;
+ unsigned int type;
+ struct irq_fwspec *fwspec = arg;
+ struct partition_desc *part;
+
+ BUG_ON(nr_irqs != 1);
+ ret = domain->ops->translate(domain, fwspec, &hwirq, &type);
+ if (ret)
+ return ret;
+
+ part = domain->host_data;
+
+ set_bit(hwirq, part->bitmap);
+ irq_set_chained_handler_and_data(irq_desc_get_irq(part->chained_desc),
+ partition_handle_irq, part);
+ irq_set_percpu_devid_partition(virq, &part->parts[hwirq].mask);
+ irq_domain_set_info(domain, virq, hwirq, &partition_irq_chip, part,
+ handle_percpu_devid_irq, NULL, NULL);
+ irq_set_status_flags(virq, IRQ_NOAUTOEN);
+
+ return 0;
+}
+
+static void partition_domain_free(struct irq_domain *domain, unsigned int virq,
+ unsigned int nr_irqs)
+{
+ struct irq_data *d;
+
+ BUG_ON(nr_irqs != 1);
+
+ d = irq_domain_get_irq_data(domain, virq);
+ irq_set_handler(virq, NULL);
+ irq_domain_reset_irq_data(d);
+}
+
+int partition_translate_id(struct partition_desc *desc, void *partition_id)
+{
+ struct partition_affinity *part = NULL;
+ int i;
+
+ for (i = 0; i < desc->nr_parts; i++) {
+ if (desc->parts[i].partition_id == partition_id) {
+ part = &desc->parts[i];
+ break;
+ }
+ }
+
+ if (WARN_ON(!part)) {
+ pr_err("Failed to find partition\n");
+ return -EINVAL;
+ }
+
+ return i;
+}
+
+struct partition_desc *partition_create_desc(struct fwnode_handle *fwnode,
+ struct partition_affinity *parts,
+ int nr_parts,
+ int chained_irq,
+ const struct irq_domain_ops *ops)
+{
+ struct partition_desc *desc;
+ struct irq_domain *d;
+
+ BUG_ON(!ops->select || !ops->translate);
+
+ desc = kzalloc(sizeof(*desc), GFP_KERNEL);
+ if (!desc)
+ return NULL;
+
+ desc->ops = *ops;
+ desc->ops.free = partition_domain_free;
+ desc->ops.alloc = partition_domain_alloc;
+
+ d = irq_domain_create_linear(fwnode, nr_parts, &desc->ops, desc);
+ if (!d)
+ goto out;
+ desc->domain = d;
+
+ desc->bitmap = kzalloc(sizeof(long) * BITS_TO_LONGS(nr_parts),
+ GFP_KERNEL);
+ if (WARN_ON(!desc->bitmap))
+ goto out;
+
+ desc->chained_desc = irq_to_desc(chained_irq);
+ desc->nr_parts = nr_parts;
+ desc->parts = parts;
+
+ return desc;
+out:
+ if (d)
+ irq_domain_remove(d);
+ kfree(desc);
+
+ return NULL;
+}
+
+struct irq_domain *partition_get_domain(struct partition_desc *dsc)
+{
+ if (dsc)
+ return dsc->domain;
+
+ return NULL;
+}
diff --git a/include/linux/irqchip/irq-partition-percpu.h b/include/linux/irqchip/irq-partition-percpu.h
new file mode 100644
index 0000000..87433a5
--- /dev/null
+++ b/include/linux/irqchip/irq-partition-percpu.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2016 ARM Limited, All Rights Reserved.
+ * Author: Marc Zyngier <marc.zyngier@xxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/fwnode.h>
+#include <linux/cpumask.h>
+#include <linux/irqdomain.h>
+
+struct partition_affinity {
+ cpumask_t mask;
+ void *partition_id;
+};
+
+struct partition_desc;
+
+#ifdef CONFIG_PARTITION_PERCPU
+int partition_translate_id(struct partition_desc *desc, void *partition_id);
+struct partition_desc *partition_create_desc(struct fwnode_handle *fwnode,
+ struct partition_affinity *parts,
+ int nr_parts,
+ int chained_irq,
+ const struct irq_domain_ops *ops);
+struct irq_domain *partition_get_domain(struct partition_desc *dsc);
+#else
+static inline int partition_translate_id(struct partition_desc *desc,
+ void *partition_id)
+{
+ return -EINVAL;
+}
+
+static inline
+struct partition_desc *partition_create_desc(struct fwnode_handle *fwnode,
+ struct partition_affinity *parts,
+ int nr_parts,
+ int chained_irq,
+ const struct irq_domain_ops *ops)
+{
+ return NULL;
+}
+
+static inline
+struct irq_domain *partition_get_domain(struct partition_desc *dsc)
+{
+ return NULL;
+}
+#endif