[RFC PATCH 1/2] irqchip: cdx-bus: add cdx-MSI domain with gic-its domain as parent

[Nipun Gupta <nipun.gupta@amd.com>]

Devices on cdx bus are dynamically detected and registered using
platform_device_register API. As these devices are not linked to
of node they need a separate MSI domain for handling device ID
to be provided to the GIC ITS domain.

Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
Signed-off-by: Nikhil Agarwal <nikhil.agarwal@amd.com>
---
CONFIG_CDX_BUS and device tree bindings for xlnx,cdx-controller-1.0
would be added as part of CDX bus patches

 drivers/irqchip/Makefile                 |   1 +
 drivers/irqchip/irq-gic-v3-its-cdx-msi.c | 113 +++++++++++++++++++++++
 include/linux/cdx/cdx.h                  |  15 +++
 3 files changed, 129 insertions(+)
 create mode 100644 drivers/irqchip/irq-gic-v3-its-cdx-msi.c
 create mode 100644 include/linux/cdx/cdx.h

diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
index 5b67450a9538..623adb8a1f20 100644
--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -115,3 +115,4 @@ obj-$(CONFIG_WPCM450_AIC)		+= irq-wpcm450-aic.o
 obj-$(CONFIG_IRQ_IDT3243X)		+= irq-idt3243x.o
 obj-$(CONFIG_APPLE_AIC)			+= irq-apple-aic.o
 obj-$(CONFIG_MCHP_EIC)			+= irq-mchp-eic.o
+obj-$(CONFIG_CDX_BUS)			+= irq-gic-v3-its-cdx-msi.o
diff --git a/drivers/irqchip/irq-gic-v3-its-cdx-msi.c b/drivers/irqchip/irq-gic-v3-its-cdx-msi.c
new file mode 100644
index 000000000000..eb17b74efdc5
--- /dev/null
+++ b/drivers/irqchip/irq-gic-v3-its-cdx-msi.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * AMD CDX bus driver MSI support
+ *
+ * Copyright(C) 2022 Xilinx Inc.
+ */
+
+#include <linux/irq.h>
+#include <linux/msi.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/of_irq.h>
+#include <linux/cdx/cdx.h>
+
+static struct irq_chip its_msi_irq_chip = {
+	.name = "ITS-fMSI",
+	.irq_mask = irq_chip_mask_parent,
+	.irq_unmask = irq_chip_unmask_parent,
+	.irq_eoi = irq_chip_eoi_parent,
+	.irq_set_affinity = msi_domain_set_affinity
+};
+
+static int its_cdx_msi_prepare(struct irq_domain *msi_domain,
+				  struct device *dev,
+				  int nvec, msi_alloc_info_t *info)
+{
+	struct msi_domain_info *msi_info;
+	struct cdx_device_data *dev_data;
+	u32 dev_id;
+
+	dev_data = dev->platform_data;
+	dev_id = dev_data->dev_id;
+
+	/* Set the device Id to be passed to the GIC-ITS */
+	info->scratchpad[0].ul = dev_id;
+
+	msi_info = msi_get_domain_info(msi_domain->parent);
+
+	/* Allocate at least 32 MSIs, and always as a power of 2 */
+	nvec = max_t(int, 32, roundup_pow_of_two(nvec));
+	return msi_info->ops->msi_prepare(msi_domain->parent, dev, nvec, info);
+}
+
+static struct msi_domain_ops its_cdx_msi_ops __ro_after_init = {
+	.msi_prepare = its_cdx_msi_prepare,
+};
+
+static struct msi_domain_info its_cdx_msi_domain_info = {
+	.flags	= (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS),
+	.ops	= &its_cdx_msi_ops,
+	.chip	= &its_msi_irq_chip,
+};
+
+static const struct of_device_id cdx_device_id[] = {
+	{.compatible = "xlnx,cdx-controller-1.0", },
+	{},
+};
+
+struct irq_domain *get_parent(struct fwnode_handle *handle)
+{
+	return irq_find_matching_fwnode(handle, DOMAIN_BUS_NEXUS);
+}
+
+static void __init its_cdx_msi_init_one(struct device_node *np,
+				    const char *name)
+{
+	struct irq_domain *parent;
+	struct irq_domain *cdx_msi_domain;
+	struct fwnode_handle *fwnode_handle;
+	struct device_node *parent_node;
+
+	parent_node = of_parse_phandle(np, "msi-parent", 0);
+
+	parent = get_parent(of_node_to_fwnode(parent_node));
+	if (!parent || !msi_get_domain_info(parent)) {
+		pr_err("%s: unable to locate ITS domain\n", name);
+		return;
+	}
+
+	fwnode_handle = of_node_to_fwnode(np);
+	cdx_msi_domain = platform_msi_create_irq_domain(fwnode_handle,
+						&its_cdx_msi_domain_info,
+						parent);
+	if (!cdx_msi_domain) {
+		pr_err("%s: unable to create cdx bus domain\n", name);
+		return;
+	}
+
+	pr_info("cdx bus MSI: %s domain created\n", name);
+}
+
+static void __init its_cdx_of_msi_init(void)
+{
+	struct device_node *np;
+
+	for (np = of_find_matching_node(NULL, cdx_device_id); np;
+	     np = of_find_matching_node(np, cdx_device_id)) {
+		if (!of_device_is_available(np))
+			continue;
+
+		its_cdx_msi_init_one(np, np->full_name);
+	}
+}
+
+static int __init its_cdx_msi_init(void)
+{
+	its_cdx_of_msi_init();
+
+	return 0;
+}
+
+early_initcall(its_cdx_msi_init);
diff --git a/include/linux/cdx/cdx.h b/include/linux/cdx/cdx.h
new file mode 100644
index 000000000000..244ad721771d
--- /dev/null
+++ b/include/linux/cdx/cdx.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * AMD CDX bus public interface
+ *
+ * Copyright(C) 2022 Xilinx Inc.
+ */
+
+#ifndef _CDX_H_
+#define _CDX_H_
+
+struct cdx_device_data {
+	int dev_id;
+};
+
+#endif /* _CDX_H_ */
-- 
2.25.1