[patch 33/33] irqchip: Add IDXD Interrupt Message Store driver

[Thomas Gleixner <tglx@linutronix.de>]

Provide a driver for the Intel IDXD IMS implementation. The implementation
uses a large message store array in device memory.

The IMS domain implementation is minimal and just provides the required
irq_chip callbacks and one domain callback which prepares the MSI
descriptor which is allocated by the core for easy usage in the irq_chip
callbacks.

The necessary iobase is stored in the irqdomain and the PASID which is
required for operation is handed in via msi_dev_cookie in the allocation
function.

Not much to see here. A few lines of code and a filled in template is all
what's needed.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 drivers/irqchip/Kconfig                    |    7 +
 drivers/irqchip/Makefile                   |    1 
 drivers/irqchip/irq-pci-intel-idxd.c       |  143 +++++++++++++++++++++++++++++
 include/linux/irqchip/irq-pci-intel-idxd.h |   22 ++++
 4 files changed, 173 insertions(+)

--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -695,4 +695,11 @@ config SUNPLUS_SP7021_INTC
 	  chained controller, routing all interrupt source in P-Chip to
 	  the primary controller on C-Chip.
 
+config PCI_INTEL_IDXD_IMS
+	tristate "Intel IDXD Interrupt Message Store controller"
+	depends on PCI_MSI
+	help
+	  Support for Intel IDXD IMS Interrupt Message Store controller
+	  with IMS slot storage in a slot array in device memory
+
 endmenu
--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -121,3 +121,4 @@ obj-$(CONFIG_IRQ_IDT3243X)		+= irq-idt32
 obj-$(CONFIG_APPLE_AIC)			+= irq-apple-aic.o
 obj-$(CONFIG_MCHP_EIC)			+= irq-mchp-eic.o
 obj-$(CONFIG_SUNPLUS_SP7021_INTC)	+= irq-sp7021-intc.o
+obj-$(CONFIG_PCI_INTEL_IDXD_IMS)	+= irq-pci-intel-idxd.o
--- /dev/null
+++ b/drivers/irqchip/irq-pci-intel-idxd.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Interrupt chip and domain for Intel IDXD with hardware array based
+ * interrupt message store (IMS).
+ */
+#include <linux/device.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
+#include <linux/msi.h>
+#include <linux/pci.h>
+
+#include <linux/irqchip/irq-pci-intel-idxd.h>
+
+MODULE_LICENSE("GPL");
+
+/**
+ * struct ims_slot - The hardware layout of a slot in the memory table
+ * @address_lo:	Lower 32bit address
+ * @address_hi:	Upper 32bit address
+ * @data:	Message data
+ * @ctrl:	Control word
+ */
+struct ims_slot {
+	u32	address_lo;
+	u32	address_hi;
+	u32	data;
+	u32	ctrl;
+} __packed;
+
+/* Bit to mask the interrupt in the control word */
+#define CTRL_VECTOR_MASKBIT	BIT(0)
+/* Bit to enable PASID in the control word */
+#define CTRL_PASID_ENABLE	BIT(3)
+/* Position of PASID.LSB in the control word */
+#define CTRL_PASID_SHIFT	12
+
+static inline void iowrite32_and_flush(u32 value, void __iomem *addr)
+{
+	iowrite32(value, addr);
+	ioread32(addr);
+}
+
+static void idxd_mask(struct irq_data *data)
+{
+	struct msi_desc *desc = irq_data_get_msi_desc(data);
+	struct ims_slot __iomem *slot = desc->data.iobase;
+	u32 cval = desc->data.cookie.value;
+
+	iowrite32_and_flush(cval | CTRL_VECTOR_MASKBIT, &slot->ctrl);
+}
+
+static void idxd_unmask(struct irq_data *data)
+{
+	struct msi_desc *desc = irq_data_get_msi_desc(data);
+	struct ims_slot __iomem *slot = desc->data.iobase;
+	u32 cval = desc->data.cookie.value;
+
+	iowrite32_and_flush(cval, &slot->ctrl);
+}
+
+static void idxd_write_msi_msg(struct irq_data *data, struct msi_msg *msg)
+{
+	struct msi_desc *desc = irq_data_get_msi_desc(data);
+	struct ims_slot __iomem *slot = desc->data.iobase;
+
+	iowrite32(msg->address_lo, &slot->address_lo);
+	iowrite32(msg->address_hi, &slot->address_hi);
+	iowrite32_and_flush(msg->data, &slot->data);
+}
+
+static void idxd_shutdown(struct irq_data *data)
+{
+	struct msi_desc *desc = irq_data_get_msi_desc(data);
+	struct ims_slot __iomem *slot = desc->data.iobase;
+
+	iowrite32(0, &slot->address_lo);
+	iowrite32(0, &slot->address_hi);
+	iowrite32(0, &slot->data);
+	iowrite32_and_flush(CTRL_VECTOR_MASKBIT, &slot->ctrl);
+}
+
+static void idxd_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
+			      struct msi_desc *desc)
+{
+	struct msi_domain_info *info = domain->host_data;
+	struct ims_slot __iomem *slot;
+
+	/* Set up the slot address for the irq_chip callbacks */
+	slot = (__force struct ims_slot __iomem *) info->data;
+	slot += desc->msi_index;
+	desc->data.iobase = slot;
+
+	/* Mask the interrupt for paranoia sake */
+	iowrite32_and_flush(CTRL_VECTOR_MASKBIT, &slot->ctrl);
+
+	/*
+	 * The caller provided PASID. Shift it to the proper position
+	 * and set the PASID enable bit.
+	 */
+	desc->data.cookie.value <<= CTRL_PASID_SHIFT;
+	desc->data.cookie.value |= CTRL_PASID_ENABLE;
+
+	arg->hwirq = desc->msi_index;
+}
+
+static const struct msi_domain_template idxd_ims_template = {
+	.chip = {
+		.name			= "PCI-IDXD",
+		.irq_mask		= idxd_mask,
+		.irq_unmask		= idxd_unmask,
+		.irq_write_msi_msg	= idxd_write_msi_msg,
+		.irq_shutdown		= idxd_shutdown,
+		.flags			= IRQCHIP_ONESHOT_SAFE,
+	},
+
+	.ops = {
+		.prepare_desc		= idxd_prepare_desc,
+	},
+
+	.info = {
+		.flags			= MSI_FLAG_ALLOC_SIMPLE_MSI_DESCS |
+					  MSI_FLAG_FREE_MSI_DESCS |
+					  MSI_FLAG_PCI_IMS,
+		.bus_token		= DOMAIN_BUS_PCI_DEVICE_IMS,
+	},
+};
+
+/**
+ * pci_intel_idxd_create_ims_domain - Create a IDXD IMS domain
+ * @pdev:	IDXD PCI device to operate on
+ * @slots:	Pointer to the mapped slot memory arrray
+ * @nr_slots:	The number of slots in the array
+ *
+ * Returns: True on success, false otherwise
+ *
+ * The domain is automatically destroyed when the @pdev is destroyed
+ */
+bool pci_intel_idxd_create_ims_domain(struct pci_dev *pdev, void __iomem *slots,
+				      unsigned int nr_slots)
+{
+	return pci_create_ims_domain(pdev, &idxd_ims_template, nr_slots, (__force void *)slots);
+}
+EXPORT_SYMBOL_GPL(pci_intel_idxd_create_ims_domain);
--- /dev/null
+++ b/include/linux/irqchip/irq-pci-intel-idxd.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* (C) Copyright 2022 Thomas Gleixner <tglx@linutronix.de> */
+
+#ifndef _LINUX_IRQCHIP_IRQ_PCI_INTEL_IDXD_H
+#define _LINUX_IRQCHIP_IRQ_PCI_INTEL_IDXD_H
+
+#include <linux/msi_api.h>
+#include <linux/bits.h>
+#include <linux/types.h>
+
+/*
+ * Conveniance macro to wrap the PASID for interrupt allocation
+ * via pci_ims_alloc_irq(pdev, INTEL_IDXD_DEV_COOKIE(pasid))
+ */
+#define INTEL_IDXD_DEV_COOKIE(pasid)	(union msi_dev_cookie) { .value = (pasid), }
+
+struct pci_dev;
+
+bool pci_intel_idxd_create_ims_domain(struct pci_dev *pdev, void __iomem *slots,
+				      unsigned int nr_slots);
+
+#endif