/*
 * Copyright (C) 2015 Broadcom Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation version 2.
 *
 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/interrupt.h>
#include <linux/irqchip/chained_irq.h>
#include <linux/irqdomain.h>
#include <linux/msi.h>
#include <linux/of_irq.h>
#include <linux/of_pci.h>
#include <linux/pci.h>

#include "pcie-iproc.h"

#define IPROC_MSI_INTR_EN_SHIFT        11
#define IPROC_MSI_INTR_EN              BIT(IPROC_MSI_INTR_EN_SHIFT)
#define IPROC_MSI_INT_N_EVENT_SHIFT    1
#define IPROC_MSI_INT_N_EVENT          BIT(IPROC_MSI_INT_N_EVENT_SHIFT)
#define IPROC_MSI_EQ_EN_SHIFT          0
#define IPROC_MSI_EQ_EN                BIT(IPROC_MSI_EQ_EN_SHIFT)

#define IPROC_MSI_EQ_MASK              0x3f

/* Max number of GIC interrupts */
#define NR_HW_IRQS                     6

/* Number of entries in each event queue */
#define EQ_LEN                         64

/* Size of each event queue memory region */
#define EQ_MEM_REGION_SIZE             SZ_4K

/* Size of each MSI address region */
#define MSI_MEM_REGION_SIZE            SZ_4K

enum iproc_msi_reg {
	IPROC_MSI_EQ_PAGE = 0,
	IPROC_MSI_EQ_PAGE_UPPER,
	IPROC_MSI_PAGE,
	IPROC_MSI_PAGE_UPPER,
	IPROC_MSI_CTRL,
	IPROC_MSI_EQ_HEAD,
	IPROC_MSI_EQ_TAIL,
	IPROC_MSI_INTS_EN,
	IPROC_MSI_REG_SIZE,
};

struct iproc_msi;

/**
 * iProc MSI group
 *
 * One MSI group is allocated per GIC interrupt, serviced by one iProc MSI
 * event queue.
 *
 * @msi: pointer to iProc MSI data
 * @gic_irq: GIC interrupt
 * @eq: Event queue number
 */
struct iproc_msi_grp {
	struct iproc_msi *msi;
	int gic_irq;
	unsigned int eq;
};

/**
 * iProc event queue based MSI
 *
 * Only meant to be used on platforms without MSI support integrated into the
 * GIC.
 *
 * @pcie: pointer to iProc PCIe data
 * @reg_offsets: MSI register offsets
 * @grps: MSI groups
 * @nr_irqs: number of total interrupts connected to GIC
 * @nr_cpus: number of toal CPUs
 * @has_inten_reg: indicates the MSI interrupt enable register needs to be
 * set explicitly (required for some legacy platforms)
 * @bitmap: MSI vector bitmap
 * @bitmap_lock: lock to protect access to the MSI bitmap
 * @nr_msi_vecs: total number of MSI vectors
 * @inner_domain: inner IRQ domain
 * @msi_domain: MSI IRQ domain
 * @nr_eq_region: required number of 4K aligned memory region for MSI event
 * queues
 * @nr_msi_region: required number of 4K aligned address region for MSI posted
 * writes
 * @eq_cpu: pointer to allocated memory region for MSI event queues
 * @eq_dma: DMA address of MSI event queues
 * @msi_addr: MSI address
 */
struct iproc_msi {
	struct iproc_pcie *pcie;
	const u16 (*reg_offsets)[IPROC_MSI_REG_SIZE];
	struct iproc_msi_grp *grps;
	int nr_irqs;
	int nr_cpus;
	bool has_inten_reg;
	unsigned long *bitmap;
	struct mutex bitmap_lock;
	unsigned int nr_msi_vecs;
	struct irq_domain *inner_domain;
	struct irq_domain *msi_domain;
	unsigned int nr_eq_region;
	unsigned int nr_msi_region;
	void *eq_cpu;
	dma_addr_t eq_dma;
	phys_addr_t msi_addr;
};

static const u16 iproc_msi_reg_paxb[NR_HW_IRQS][IPROC_MSI_REG_SIZE] = {
	{ 0x200, 0x2c0, 0x204, 0x2c4, 0x210, 0x250, 0x254, 0x208 },
	{ 0x200, 0x2c0, 0x204, 0x2c4, 0x214, 0x258, 0x25c, 0x208 },
	{ 0x200, 0x2c0, 0x204, 0x2c4, 0x218, 0x260, 0x264, 0x208 },
	{ 0x200, 0x2c0, 0x204, 0x2c4, 0x21c, 0x268, 0x26c, 0x208 },
	{ 0x200, 0x2c0, 0x204, 0x2c4, 0x220, 0x270, 0x274, 0x208 },
	{ 0x200, 0x2c0, 0x204, 0x2c4, 0x224, 0x278, 0x27c, 0x208 },
};

static const u16 iproc_msi_reg_paxc[NR_HW_IRQS][IPROC_MSI_REG_SIZE] = {
	{ 0xc00, 0xc04, 0xc08, 0xc0c, 0xc40, 0xc50, 0xc60 },
	{ 0xc10, 0xc14, 0xc18, 0xc1c, 0xc44, 0xc54, 0xc64 },
	{ 0xc20, 0xc24, 0xc28, 0xc2c, 0xc48, 0xc58, 0xc68 },
	{ 0xc30, 0xc34, 0xc38, 0xc3c, 0xc4c, 0xc5c, 0xc6c },
};

static inline u32 iproc_msi_read_reg(struct iproc_msi *msi,
				     enum iproc_msi_reg reg,
				     unsigned int eq)
{
	struct iproc_pcie *pcie = msi->pcie;

	return readl_relaxed(pcie->base + msi->reg_offsets[eq][reg]);
}

static inline void iproc_msi_write_reg(struct iproc_msi *msi,
				       enum iproc_msi_reg reg,
				       int eq, u32 val)
{
	struct iproc_pcie *pcie = msi->pcie;

	writel_relaxed(val, pcie->base + msi->reg_offsets[eq][reg]);
}

static inline u32 hwirq_to_group(struct iproc_msi *msi, unsigned long hwirq)
{
	return (hwirq % msi->nr_irqs);
}

static inline unsigned int iproc_msi_addr_offset(struct iproc_msi *msi,
						 unsigned long hwirq)
{
	if (msi->nr_msi_region > 1)
		return hwirq_to_group(msi, hwirq) * MSI_MEM_REGION_SIZE;
	else
		return hwirq_to_group(msi, hwirq) * sizeof(u32);
}

static inline unsigned int iproc_msi_eq_offset(struct iproc_msi *msi, u32 eq)
{
	if (msi->nr_eq_region > 1)
		return eq * EQ_MEM_REGION_SIZE;
	else
		return eq * EQ_LEN * sizeof(u32);
}

static struct irq_chip iproc_msi_irq_chip = {
	.name = "iProc-MSI",
};

static struct msi_domain_info iproc_msi_domain_info = {
	.flags = MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS |
		MSI_FLAG_PCI_MSIX,
	.chip = &iproc_msi_irq_chip,
};

/*
 * In iProc PCIe core, each MSI group is serviced by a GIC interrupt and a
 * dedicated event queue.  Each MSI group can support up to 64 MSI vectors.
 *
 * The number of MSI groups varies between different iProc SoCs.  The total
 * number of CPU cores also varies.  To support MSI IRQ affinity, we
 * distribute GIC interrupts across all available CPUs.  MSI vector is moved
 * from one GIC interrupt to another to steer to the target CPU.
 *
 * Assuming:
 * - the number of MSI groups is M
 * - the number of CPU cores is N
 * - M is always a multiple of N
 *
 * Total number of raw MSI vectors = M * 64
 * Total number of supported MSI vectors = (M * 64) / N
 */
static inline int hwirq_to_cpu(struct iproc_msi *msi, unsigned long hwirq)
{
	return (hwirq % msi->nr_cpus);
}

static inline unsigned long hwirq_to_canonical_hwirq(struct iproc_msi *msi,
						     unsigned long hwirq)
{
	return (hwirq - hwirq_to_cpu(msi, hwirq));
}

static int iproc_msi_irq_set_affinity(struct irq_data *data,
				      const struct cpumask *mask, bool force)
{
	struct iproc_msi *msi = irq_data_get_irq_chip_data(data);
	int target_cpu = cpumask_first(mask);
	int curr_cpu;

	curr_cpu = hwirq_to_cpu(msi, data->hwirq);
	if (curr_cpu == target_cpu)
		return IRQ_SET_MASK_OK_DONE;

	/* steer MSI to the target CPU */
	data->hwirq = hwirq_to_canonical_hwirq(msi, data->hwirq) + target_cpu;

	return IRQ_SET_MASK_OK;
}

static void iproc_msi_irq_compose_msi_msg(struct irq_data *data,
					  struct msi_msg *msg)
{
	struct iproc_msi *msi = irq_data_get_irq_chip_data(data);
	dma_addr_t addr;

	addr = msi->msi_addr + iproc_msi_addr_offset(msi, data->hwirq);
	msg->address_lo = lower_32_bits(addr);
	msg->address_hi = upper_32_bits(addr);
	msg->data = data->hwirq;
}

static struct irq_chip iproc_msi_bottom_irq_chip = {
	.name = "MSI",
	.irq_set_affinity = iproc_msi_irq_set_affinity,
	.irq_compose_msi_msg = iproc_msi_irq_compose_msi_msg,
};

static int iproc_msi_irq_domain_alloc(struct irq_domain *domain,
				      unsigned int virq, unsigned int nr_irqs,
				      void *args)
{
	struct iproc_msi *msi = domain->host_data;
	int hwirq;

	mutex_lock(&msi->bitmap_lock);

	/* Allocate 'nr_cpus' number of MSI vectors each time */
	hwirq = bitmap_find_next_zero_area(msi->bitmap, msi->nr_msi_vecs, 0,
					   msi->nr_cpus, 0);
	if (hwirq < msi->nr_msi_vecs) {
		bitmap_set(msi->bitmap, hwirq, msi->nr_cpus);
	} else {
		mutex_unlock(&msi->bitmap_lock);
		return -ENOSPC;
	}

	mutex_unlock(&msi->bitmap_lock);

	irq_domain_set_info(domain, virq, hwirq, &iproc_msi_bottom_irq_chip,
			    domain->host_data, handle_simple_irq, NULL, NULL);

	return 0;
}

static void iproc_msi_irq_domain_free(struct irq_domain *domain,
				      unsigned int virq, unsigned int nr_irqs)
{
	struct irq_data *data = irq_domain_get_irq_data(domain, virq);
	struct iproc_msi *msi = irq_data_get_irq_chip_data(data);
	unsigned int hwirq;

	mutex_lock(&msi->bitmap_lock);

	hwirq = hwirq_to_canonical_hwirq(msi, data->hwirq);
	bitmap_clear(msi->bitmap, hwirq, msi->nr_cpus);

	mutex_unlock(&msi->bitmap_lock);

	irq_domain_free_irqs_parent(domain, virq, nr_irqs);
}

static const struct irq_domain_ops msi_domain_ops = {
	.alloc = iproc_msi_irq_domain_alloc,
	.free = iproc_msi_irq_domain_free,
};

static inline u32 decode_msi_hwirq(struct iproc_msi *msi, u32 eq, u32 head)
{
	u32 *msg, hwirq;
	unsigned int offs;

	offs = iproc_msi_eq_offset(msi, eq) + head * sizeof(u32);
	msg = (u32 *)(msi->eq_cpu + offs);
	hwirq = *msg & IPROC_MSI_EQ_MASK;

	/*
	 * Since we have multiple hwirq mapped to a single MSI vector,
	 * now we need to derive the hwirq at CPU0.  It can then be used to
	 * mapped back to virq.
	 */
	return hwirq_to_canonical_hwirq(msi, hwirq);
}

static void iproc_msi_handler(struct irq_desc *desc)
{
	struct irq_chip *chip = irq_desc_get_chip(desc);
	struct iproc_msi_grp *grp;
	struct iproc_msi *msi;
	struct iproc_pcie *pcie;
	u32 eq, head, tail, nr_events;
	unsigned long hwirq;
	int virq;

	chained_irq_enter(chip, desc);

	grp = irq_desc_get_handler_data(desc);
	msi = grp->msi;
	pcie = msi->pcie;
	eq = grp->eq;

	/*
	 * iProc MSI event queue is tracked by head and tail pointers.  Head
	 * pointer indicates the next entry (MSI data) to be consumed by SW in
	 * the queue and needs to be updated by SW.  iProc MSI core uses the
	 * tail pointer as the next data insertion point.
	 *
	 * Entries between head and tail pointers contain valid MSI data.  MSI
	 * data is guaranteed to be in the event queue memory before the tail
	 * pointer is updated by the iProc MSI core.
	 */
	head = iproc_msi_read_reg(msi, IPROC_MSI_EQ_HEAD,
				  eq) & IPROC_MSI_EQ_MASK;
	do {
		tail = iproc_msi_read_reg(msi, IPROC_MSI_EQ_TAIL,
					  eq) & IPROC_MSI_EQ_MASK;

		/*
		 * Figure out total number of events (MSI data) to be
		 * processed.
		 */
		nr_events = (tail < head) ?
			(EQ_LEN - (head - tail)) : (tail - head);
		if (!nr_events)
			break;

		/* process all outstanding events */
		while (nr_events--) {
			hwirq = decode_msi_hwirq(msi, eq, head);
			virq = irq_find_mapping(msi->inner_domain, hwirq);
			generic_handle_irq(virq);

			head++;
			head %= EQ_LEN;
		}

		/*
		 * Now all outstanding events have been processed.  Update the
		 * head pointer.
		 */
		iproc_msi_write_reg(msi, IPROC_MSI_EQ_HEAD, eq, head);

		/*
		 * Now go read the tail pointer again to see if there are new
		 * oustanding events that came in during the above window.
		 */
	} while (true);

	chained_irq_exit(chip, desc);
}

static void iproc_msi_enable(struct iproc_msi *msi)
{
	int i, eq;
	u32 val;

	/* Program memory region for each event queue */
	for (i = 0; i < msi->nr_eq_region; i++) {
		dma_addr_t addr = msi->eq_dma + (i * EQ_MEM_REGION_SIZE);

		iproc_msi_write_reg(msi, IPROC_MSI_EQ_PAGE, i,
				    lower_32_bits(addr));
		iproc_msi_write_reg(msi, IPROC_MSI_EQ_PAGE_UPPER, i,
				    upper_32_bits(addr));
	}

	/* Program address region for MSI posted writes */
	for (i = 0; i < msi->nr_msi_region; i++) {
		phys_addr_t addr = msi->msi_addr + (i * MSI_MEM_REGION_SIZE);

		iproc_msi_write_reg(msi, IPROC_MSI_PAGE, i,
				    lower_32_bits(addr));
		iproc_msi_write_reg(msi, IPROC_MSI_PAGE_UPPER, i,
				    upper_32_bits(addr));
	}

	for (eq = 0; eq < msi->nr_irqs; eq++) {
		/* Enable MSI event queue */
		val = IPROC_MSI_INTR_EN | IPROC_MSI_INT_N_EVENT |
			IPROC_MSI_EQ_EN;
		iproc_msi_write_reg(msi, IPROC_MSI_CTRL, eq, val);

		/*
		 * Some legacy platforms require the MSI interrupt enable
		 * register to be set explicitly.
		 */
		if (msi->has_inten_reg) {
			val = iproc_msi_read_reg(msi, IPROC_MSI_INTS_EN, eq);
			val |= BIT(eq);
			iproc_msi_write_reg(msi, IPROC_MSI_INTS_EN, eq, val);
		}
	}
}

static void iproc_msi_disable(struct iproc_msi *msi)
{
	u32 eq, val;

	for (eq = 0; eq < msi->nr_irqs; eq++) {
		if (msi->has_inten_reg) {
			val = iproc_msi_read_reg(msi, IPROC_MSI_INTS_EN, eq);
			val &= ~BIT(eq);
			iproc_msi_write_reg(msi, IPROC_MSI_INTS_EN, eq, val);
		}

		val = iproc_msi_read_reg(msi, IPROC_MSI_CTRL, eq);
		val &= ~(IPROC_MSI_INTR_EN | IPROC_MSI_INT_N_EVENT |
			 IPROC_MSI_EQ_EN);
		iproc_msi_write_reg(msi, IPROC_MSI_CTRL, eq, val);
	}
}

static int iproc_msi_alloc_domains(struct device_node *node,
				   struct iproc_msi *msi)
{
	msi->inner_domain = irq_domain_add_linear(NULL, msi->nr_msi_vecs,
						  &msi_domain_ops, msi);
	if (!msi->inner_domain)
		return -ENOMEM;

	msi->msi_domain = pci_msi_create_irq_domain(of_node_to_fwnode(node),
						    &iproc_msi_domain_info,
						    msi->inner_domain);
	if (!msi->msi_domain) {
		irq_domain_remove(msi->inner_domain);
		return -ENOMEM;
	}

	return 0;
}

static void iproc_msi_free_domains(struct iproc_msi *msi)
{
	if (msi->msi_domain)
		irq_domain_remove(msi->msi_domain);

	if (msi->inner_domain)
		irq_domain_remove(msi->inner_domain);
}

static void iproc_msi_irq_free(struct iproc_msi *msi, unsigned int cpu)
{
	int i;

	for (i = cpu; i < msi->nr_irqs; i += msi->nr_cpus) {
		irq_set_chained_handler_and_data(msi->grps[i].gic_irq,
						 NULL, NULL);
	}
}

static int iproc_msi_irq_setup(struct iproc_msi *msi, unsigned int cpu)
{
	int i, ret;
	cpumask_var_t mask;
	struct iproc_pcie *pcie = msi->pcie;

	for (i = cpu; i < msi->nr_irqs; i += msi->nr_cpus) {
		irq_set_chained_handler_and_data(msi->grps[i].gic_irq,
						 iproc_msi_handler,
						 &msi->grps[i]);
		/* Dedicate GIC interrupt to each CPU core */
		if (alloc_cpumask_var(&mask, GFP_KERNEL)) {
			cpumask_clear(mask);
			cpumask_set_cpu(cpu, mask);
			ret = irq_set_affinity(msi->grps[i].gic_irq, mask);
			if (ret)
				dev_err(pcie->dev,
					"failed to set affinity for IRQ%d\n",
					msi->grps[i].gic_irq);
			free_cpumask_var(mask);
		} else {
			dev_err(pcie->dev, "failed to alloc CPU mask\n");
			ret = -EINVAL;
		}

		if (ret) {
			/* Free all configured/unconfigured IRQs */
			iproc_msi_irq_free(msi, cpu);
			return ret;
		}
	}

	return 0;
}

int iproc_msi_init(struct iproc_pcie *pcie, struct device_node *node)
{
	struct iproc_msi *msi;
	int i, ret;
	unsigned int cpu;

	if (!of_device_is_compatible(node, "brcm,iproc-msi"))
		return -ENODEV;

	if (!of_find_property(node, "msi-controller", NULL))
		return -ENODEV;

	if (pcie->msi)
		return -EBUSY;

	msi = devm_kzalloc(pcie->dev, sizeof(*msi), GFP_KERNEL);
	if (!msi)
		return -ENOMEM;

	msi->pcie = pcie;
	pcie->msi = msi;
	msi->msi_addr = pcie->base_addr;
	mutex_init(&msi->bitmap_lock);
	msi->nr_cpus = num_possible_cpus();

	msi->nr_irqs = of_irq_count(node);
	if (!msi->nr_irqs) {
		dev_err(pcie->dev, "found no MSI GIC interrupt\n");
		return -ENODEV;
	}

	if (msi->nr_irqs > NR_HW_IRQS) {
		dev_warn(pcie->dev, "too many MSI GIC interrupts defined %d\n",
			 msi->nr_irqs);
		msi->nr_irqs = NR_HW_IRQS;
	}

	if (msi->nr_irqs < msi->nr_cpus) {
		dev_err(pcie->dev,
			"not enough GIC interrupts for MSI affinity\n");
		return -EINVAL;
	}

	if (msi->nr_irqs % msi->nr_cpus != 0) {
		msi->nr_irqs -= msi->nr_irqs % msi->nr_cpus;
		dev_warn(pcie->dev, "Reducing number of interrupts to %d\n",
			 msi->nr_irqs);
	}

	switch (pcie->type) {
	case IPROC_PCIE_PAXB:
		msi->reg_offsets = iproc_msi_reg_paxb;
		msi->nr_eq_region = 1;
		msi->nr_msi_region = 1;
		break;
	case IPROC_PCIE_PAXC:
		msi->reg_offsets = iproc_msi_reg_paxc;
		msi->nr_eq_region = msi->nr_irqs;
		msi->nr_msi_region = msi->nr_irqs;
		break;
	default:
		dev_err(pcie->dev, "incompatible iProc PCIe interface\n");
		return -EINVAL;
	}

	if (of_find_property(node, "brcm,pcie-msi-inten", NULL))
		msi->has_inten_reg = true;

	msi->nr_msi_vecs = msi->nr_irqs * EQ_LEN;
	msi->bitmap = devm_kcalloc(pcie->dev, BITS_TO_LONGS(msi->nr_msi_vecs),
				   sizeof(*msi->bitmap), GFP_KERNEL);
	if (!msi->bitmap)
		return -ENOMEM;

	msi->grps = devm_kcalloc(pcie->dev, msi->nr_irqs, sizeof(*msi->grps),
				 GFP_KERNEL);
	if (!msi->grps)
		return -ENOMEM;

	for (i = 0; i < msi->nr_irqs; i++) {
		unsigned int irq = irq_of_parse_and_map(node, i);

		if (!irq) {
			dev_err(pcie->dev, "unable to parse/map interrupt\n");
			ret = -ENODEV;
			goto free_irqs;
		}
		msi->grps[i].gic_irq = irq;
		msi->grps[i].msi = msi;
		msi->grps[i].eq = i;
	}

	/* Reserve memory for event queue and make sure memories are zeroed */
	msi->eq_cpu = dma_zalloc_coherent(pcie->dev,
					  msi->nr_eq_region * EQ_MEM_REGION_SIZE,
					  &msi->eq_dma, GFP_KERNEL);
	if (!msi->eq_cpu) {
		ret = -ENOMEM;
		goto free_irqs;
	}

	ret = iproc_msi_alloc_domains(node, msi);
	if (ret) {
		dev_err(pcie->dev, "failed to create MSI domains\n");
		goto free_eq_dma;
	}

	for_each_online_cpu(cpu) {
		ret = iproc_msi_irq_setup(msi, cpu);
		if (ret)
			goto free_msi_irq;
	}

	iproc_msi_enable(msi);

	return 0;

free_msi_irq:
	for_each_online_cpu(cpu)
		iproc_msi_irq_free(msi, cpu);
	iproc_msi_free_domains(msi);

free_eq_dma:
	dma_free_coherent(pcie->dev, msi->nr_eq_region * EQ_MEM_REGION_SIZE,
			  msi->eq_cpu, msi->eq_dma);

free_irqs:
	for (i = 0; i < msi->nr_irqs; i++) {
		if (msi->grps[i].gic_irq)
			irq_dispose_mapping(msi->grps[i].gic_irq);
	}
	pcie->msi = NULL;
	return ret;
}
EXPORT_SYMBOL(iproc_msi_init);

void iproc_msi_exit(struct iproc_pcie *pcie)
{
	struct iproc_msi *msi = pcie->msi;
	unsigned int i, cpu;

	if (!msi)
		return;

	iproc_msi_disable(msi);

	for_each_online_cpu(cpu)
		iproc_msi_irq_free(msi, cpu);

	iproc_msi_free_domains(msi);

	dma_free_coherent(pcie->dev, msi->nr_eq_region * EQ_MEM_REGION_SIZE,
			  msi->eq_cpu, msi->eq_dma);

	for (i = 0; i < msi->nr_irqs; i++) {
		if (msi->grps[i].gic_irq)
			irq_dispose_mapping(msi->grps[i].gic_irq);
	}
}
EXPORT_SYMBOL(iproc_msi_exit);