[PATCH v5 09/19] drivers: base: Add MSI domain support for non-PCI devices

Marc Zyngier
2015-07-23T09:30:48Z

With the msi_list and the msi_domain properties now being at the
generic device level, it is starting to be relatively easy to offer
a generic way of providing non-PCI MSIs.

The two major hurdles with this idea are:

- Lack of global ID that identifies a device: this is worked around by
having a global ID allocator for each device that gets enrolled in
the platform MSI subsystem

- Lack of standard way to write the message in the generating device.
This is solved by mandating driver code to provide a write_msg
callback, so that everyone can have their own square wheel

Apart from that, the API is fairly straightforward:

- platform_msi_create_irq_domain creates an MSI domain that gets
tagged with DOMAIN_BUS_PLATFORM_MSI

- platform_msi_domain_alloc_irqs allocate MSIs for a given device,
populating the msi_list

- platform_msi_domain_free_irqs does what is written on the tin

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
drivers/base/Makefile | 1 +
drivers/base/platform-msi.c | 282 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/msi.h | 15 +++
3 files changed, 298 insertions(+)
create mode 100644 drivers/base/platform-msi.c

diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 527d291..6b2a84e 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_REGMAP) += regmap/
obj-$(CONFIG_SOC_BUS) += soc.o
obj-$(CONFIG_PINCTRL) += pinctrl.o
obj-$(CONFIG_DEV_COREDUMP) += devcoredump.o
+obj-$(CONFIG_GENERIC_MSI_IRQ_DOMAIN) += platform-msi.o

ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG

diff --git a/drivers/base/platform-msi.c b/drivers/base/platform-msi.c
new file mode 100644
index 0000000..1857a5d
--- /dev/null
+++ b/drivers/base/platform-msi.c
@@ -0,0 +1,282 @@
+/*
+ * MSI framework for platform devices
+ *
+ * Copyright (C) 2015 ARM Limited, All Rights Reserved.
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * 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/device.h>
+#include <linux/idr.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
+#include <linux/msi.h>
+#include <linux/slab.h>
+
+#define DEV_ID_SHIFT 24
+
+/*
+ * Internal data structure containing a (made up, but unique) devid
+ * and the callback to write the MSI message.
+ */
+struct platform_msi_priv_data {
+ irq_write_msi_msg_t write_msg;
+ int devid;
+};
+
+/* The devid allocator */
+static DEFINE_IDA(platform_msi_devid_ida);
+
+#ifdef GENERIC_MSI_DOMAIN_OPS
+/*
+ * Convert an msi_desc to a globaly unique identifier (per-device
+ * devid + msi_desc position in the msi_list).
+ */
+static irq_hw_number_t platform_msi_calc_hwirq(struct msi_desc *desc)
+{
+ u32 devid;
+
+ devid = desc->platform.msi_priv_data->devid;
+
+ return (devid << (32 - DEV_ID_SHIFT)) | desc->platform.msi_index;
+}
+
+static void platform_msi_set_desc(msi_alloc_info_t *arg, struct msi_desc *desc)
+{
+ arg->desc = desc;
+ arg->hwirq = platform_msi_calc_hwirq(desc);
+}
+
+static int platform_msi_init(struct irq_domain *domain,
+ struct msi_domain_info *info,
+ unsigned int virq, irq_hw_number_t hwirq,
+ msi_alloc_info_t *arg)
+{
+ struct irq_data *data;
+
+ irq_domain_set_hwirq_and_chip(domain, virq, hwirq,
+ info->chip, info->chip_data);
+
+ /*
+ * Save the MSI descriptor in handler_data so that the
+ * irq_write_msi_msg callback can retrieve it (and the
+ * associated device).
+ */
+ data = irq_domain_get_irq_data(domain, virq);
+ data->handler_data = arg->desc;
+
+ return 0;
+}
+#else
+#define platform_msi_set_desc NULL
+#define platform_msi_init NULL
+#endif
+
+static void platform_msi_update_dom_ops(struct msi_domain_info *info)
+{
+ struct msi_domain_ops *ops = info->ops;
+
+ BUG_ON(!ops);
+
+ if (ops->msi_init == NULL)
+ ops->msi_init = platform_msi_init;
+ if (ops->set_desc == NULL)
+ ops->set_desc = platform_msi_set_desc;
+}
+
+static void platform_msi_write_msg(struct irq_data *data, struct msi_msg *msg)
+{
+ struct msi_desc *desc = irq_data_get_irq_handler_data(data);
+ struct platform_msi_priv_data *priv_data;
+
+ priv_data = desc->platform.msi_priv_data;
+
+ priv_data->write_msg(desc, msg);
+}
+
+static void platform_msi_update_chip_ops(struct msi_domain_info *info)
+{
+ struct irq_chip *chip = info->chip;
+
+ BUG_ON(!chip);
+ if (!chip->irq_mask)
+ chip->irq_mask = irq_chip_mask_parent;
+ if (!chip->irq_unmask)
+ chip->irq_unmask = irq_chip_unmask_parent;
+ if (!chip->irq_eoi)
+ chip->irq_eoi = irq_chip_eoi_parent;
+ if (!chip->irq_set_affinity)
+ chip->irq_set_affinity = msi_domain_set_affinity;
+ if (!chip->irq_write_msi_msg)
+ chip->irq_write_msi_msg = platform_msi_write_msg;
+}
+
+static void platform_msi_free_descs(struct device *dev)
+{
+ struct msi_desc *desc, *tmp;
+
+ list_for_each_entry_safe(desc, tmp, dev_to_msi_list(dev), list) {
+ list_del(&desc->list);
+ free_msi_entry(desc);
+ }
+}
+
+static int platform_msi_alloc_descs(struct device *dev, int nvec,
+ struct platform_msi_priv_data *data)
+
+{
+ int i;
+
+ for (i = 0; i < nvec; i++) {
+ struct msi_desc *desc;
+
+ desc = alloc_msi_entry(dev);
+ if (!desc)
+ break;
+
+ desc->platform.msi_priv_data = data;
+ desc->platform.msi_index = i;
+ desc->nvec_used = 1;
+
+ list_add_tail(&desc->list, dev_to_msi_list(dev));
+ }
+
+ if (i != nvec) {
+ /* Clean up the mess */
+ platform_msi_free_descs(dev);
+
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+/**
+ * platform_msi_create_irq_domain - Create a platform MSI interrupt domain
+ * @np: Optional device-tree node of the interrupt controller
+ * @info: MSI domain info
+ * @parent: Parent irq domain
+ *
+ * Updates the domain and chip ops and creates a platform MSI
+ * interrupt domain.
+ *
+ * Returns:
+ * A domain pointer or NULL in case of failure.
+ */
+struct irq_domain *platform_msi_create_irq_domain(struct device_node *np,
+ struct msi_domain_info *info,
+ struct irq_domain *parent)
+{
+ struct irq_domain *domain;
+
+ if (info->flags & MSI_FLAG_USE_DEF_DOM_OPS)
+ platform_msi_update_dom_ops(info);
+ if (info->flags & MSI_FLAG_USE_DEF_CHIP_OPS)
+ platform_msi_update_chip_ops(info);
+
+ domain = msi_create_irq_domain(np, info, parent);
+ if (domain)
+ domain->bus_token = DOMAIN_BUS_PLATFORM_MSI;
+
+ return domain;
+}
+
+/**
+ * platform_msi_domain_alloc_irqs - Allocate MSI interrupts for @dev
+ * @dev: The device for which to allocate interrupts
+ * @nvec: The number of interrupts to allocate
+ * @write_msi_msg: Callback to write an interrupt message for @dev
+ *
+ * Returns:
+ * Zero for success, or an error code in case of failure
+ */
+int platform_msi_domain_alloc_irqs(struct device *dev, unsigned int nvec,
+ irq_write_msi_msg_t write_msi_msg)
+{
+ struct platform_msi_priv_data *priv_data;
+ int err;
+
+ /*
+ * Limit the number of interrupts to 256 per device. Should we
+ * need to bump this up, DEV_ID_SHIFT should be adjusted
+ * accordingly (which would impact the max number of MSI
+ * capable devices).
+ */
+ if (!dev->msi_domain || !write_msi_msg || !nvec ||
+ nvec > (1 << (32 - DEV_ID_SHIFT)))
+ return -EINVAL;
+
+ if (dev->msi_domain->bus_token != DOMAIN_BUS_PLATFORM_MSI) {
+ dev_err(dev, "Incompatible msi_domain, giving up\n");
+ return -EINVAL;
+ }
+
+ /* Already had a helping of MSI? Greed... */
+ if (!list_empty(dev_to_msi_list(dev)))
+ return -EBUSY;
+
+ priv_data = kzalloc(sizeof(*priv_data), GFP_KERNEL);
+ if (!priv_data)
+ return -ENOMEM;
+
+ priv_data->devid = ida_simple_get(&platform_msi_devid_ida,
+ 0, 1 << DEV_ID_SHIFT, GFP_KERNEL);
+ if (priv_data->devid < 0) {
+ err = priv_data->devid;
+ goto out_free_data;
+ }
+
+ priv_data->write_msg = write_msi_msg;
+
+ err = platform_msi_alloc_descs(dev, nvec, priv_data);
+ if (err)
+ goto out_free_id;
+
+ err = msi_domain_alloc_irqs(dev->msi_domain, dev, nvec);
+ if (err)
+ goto out_free_desc;
+
+ return 0;
+
+out_free_desc:
+ platform_msi_free_descs(dev);
+out_free_id:
+ ida_simple_remove(&platform_msi_devid_ida, priv_data->devid);
+out_free_data:
+ kfree(priv_data);
+
+ return err;
+}
+
+/**
+ * platform_msi_domain_free_irqs - Free MSI interrupts for @dev
+ * @dev: The device for which to free interrupts
+ */
+void platform_msi_domain_free_irqs(struct device *dev)
+{
+ struct msi_desc *desc;
+
+ desc = first_msi_entry(dev);
+ if (desc) {
+ struct platform_msi_priv_data *data;
+
+ data = desc->platform.msi_priv_data;
+
+ ida_simple_remove(&platform_msi_devid_ida, data->devid);
+ kfree(data);
+ }
+
+ msi_domain_free_irqs(dev->msi_domain, dev);
+ platform_msi_free_descs(dev);
+}
diff --git a/include/linux/msi.h b/include/linux/msi.h
index c10ec56..c4e6e83 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -18,6 +18,11 @@ struct pci_dev;
void __get_cached_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg);

+typedef void (*irq_write_msi_msg_t)(struct msi_desc *desc,
+ struct msi_msg *msg);
+
+struct platform_msi_priv_data;
+
struct msi_desc {
struct list_head list;
unsigned int irq;
@@ -42,6 +47,10 @@ struct msi_desc {
void __iomem *mask_base;
};
};
+ struct {
+ struct platform_msi_priv_data *msi_priv_data;
+ u16 msi_index;
+ } platform;
};
};

@@ -228,6 +237,12 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
void msi_domain_free_irqs(struct irq_domain *domain, struct device *dev);
struct msi_domain_info *msi_get_domain_info(struct irq_domain *domain);

+struct irq_domain *platform_msi_create_irq_domain(struct device_node *np,
+ struct msi_domain_info *info,
+ struct irq_domain *parent);
+int platform_msi_domain_alloc_irqs(struct device *dev, unsigned int nvec,
+ irq_write_msi_msg_t write_msi_msg);
+void platform_msi_domain_free_irqs(struct device *dev);
#endif /* CONFIG_GENERIC_MSI_IRQ_DOMAIN */

#ifdef CONFIG_PCI_MSI_IRQ_DOMAIN
--
2.1.4