drivers/base: Add MSI domain support for non-PCI devices

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

[ tglx: Created a seperate struct platform_msi_desc and added
kerneldoc entries ]

Signed-off-by: Marc Zyngier <[e-mail]>
Cc: <[e-mail]>
Cc: Yijing Wang <[e-mail]>
Cc: Ma Jun <[e-mail]>
Cc: Lorenzo Pieralisi <[e-mail]>
Cc: Duc Dang <[e-mail]>
Cc: Hanjun Guo <[e-mail]>
Cc: Bjorn Helgaas <[e-mail]>
Cc: Jiang Liu <[e-mail]>
Cc: Jason Cooper <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Thomas Gleixner <[e-mail]>

drivers/base/Makefile

···
 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
 

drivers/base/platform-msi.c

···
+/*
+ * MSI framework for platform devices
+ *
+ * Copyright (C) 2015 ARM Limited, All Rights Reserved.
+ * Author: Marc Zyngier <[e-mail]>
+ *
+ * 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);
+}

include/linux/msi.h

···
 struct irq_data;
 struct msi_desc;
 struct pci_dev;
+struct platform_msi_priv_data;
 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);
+
+/**
+ * platform_msi_desc - Platform device specific msi descriptor data
+ * @msi_priv_data:	Pointer to platform private data
+ * @msi_index:		The index of the MSI descriptor for multi MSI
+ */
+struct platform_msi_desc {
+	struct platform_msi_priv_data	*msi_priv_data;
+	u16				msi_index;
+};
 
 /**
  * struct msi_desc - Descriptor structure for MSI based interrupts
···
  * @default_irq:[PCI MSI/X] The default pre-assigned non-MSI irq
  * @mask_pos:	[PCI MSI]   Mask register position
  * @mask_base:	[PCI MSI-X] Mask register base address
+ * @platform:	[platform]  Platform device specific msi descriptor data
  */
 struct msi_desc {
 	/* Shared device/bus type independent data */
···
 		 * anonymous for now as it would require an immediate
 		 * tree wide cleanup.
 		 */
+		struct platform_msi_desc platform;
 	};
 };
 
···
 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