// SPDX-License-Identifier: GPL-2.0
#include <linux/irqchip/chained_irq.h>
#include <linux/irqdomain.h>
#include <linux/pci-ecam.h>
#include <linux/delay.h>
#include <linux/msi.h>
#include <linux/of_address.h>

#define MSI_MAX			256

#define SMP8759_MUX		0x48
#define SMP8759_TEST_OUT	0x74
#define SMP8759_DOORBELL	0x7c
#define SMP8759_STATUS		0x80
#define SMP8759_ENABLE		0xa0

struct tango_pcie {
	DECLARE_BITMAP(used_msi, MSI_MAX);
	u64			msi_doorbell;
	spinlock_t		used_msi_lock;
	void __iomem		*base;
	struct irq_domain	*dom;
};

static void tango_msi_isr(struct irq_desc *desc)
{
	struct irq_chip *chip = irq_desc_get_chip(desc);
	struct tango_pcie *pcie = irq_desc_get_handler_data(desc);
	unsigned long status, base, virq, idx, pos = 0;

	chained_irq_enter(chip, desc);
	spin_lock(&pcie->used_msi_lock);

	while ((pos = find_next_bit(pcie->used_msi, MSI_MAX, pos)) < MSI_MAX) {
		base = round_down(pos, 32);
		status = readl_relaxed(pcie->base + SMP8759_STATUS + base / 8);
		for_each_set_bit(idx, &status, 32) {
			virq = irq_find_mapping(pcie->dom, base + idx);
			generic_handle_irq(virq);
		}
		pos = base + 32;
	}

	spin_unlock(&pcie->used_msi_lock);
	chained_irq_exit(chip, desc);
}

static void tango_ack(struct irq_data *d)
{
	struct tango_pcie *pcie = d->chip_data;
	u32 offset = (d->hwirq / 32) * 4;
	u32 bit = BIT(d->hwirq % 32);

	writel_relaxed(bit, pcie->base + SMP8759_STATUS + offset);
}

static void update_msi_enable(struct irq_data *d, bool unmask)
{
	unsigned long flags;
	struct tango_pcie *pcie = d->chip_data;
	u32 offset = (d->hwirq / 32) * 4;
	u32 bit = BIT(d->hwirq % 32);
	u32 val;

	spin_lock_irqsave(&pcie->used_msi_lock, flags);
	val = readl_relaxed(pcie->base + SMP8759_ENABLE + offset);
	val = unmask ? val | bit : val & ~bit;
	writel_relaxed(val, pcie->base + SMP8759_ENABLE + offset);
	spin_unlock_irqrestore(&pcie->used_msi_lock, flags);
}

static void tango_mask(struct irq_data *d)
{
	update_msi_enable(d, false);
}

static void tango_unmask(struct irq_data *d)
{
	update_msi_enable(d, true);
}

static int tango_set_affinity(struct irq_data *d, const struct cpumask *mask,
			      bool force)
{
	return -EINVAL;
}

static void tango_compose_msi_msg(struct irq_data *d, struct msi_msg *msg)
{
	struct tango_pcie *pcie = d->chip_data;
	msg->address_lo = lower_32_bits(pcie->msi_doorbell);
	msg->address_hi = upper_32_bits(pcie->msi_doorbell);
	msg->data = d->hwirq;
}

static struct irq_chip tango_chip = {
	.irq_ack		= tango_ack,
	.irq_mask		= tango_mask,
	.irq_unmask		= tango_unmask,
	.irq_set_affinity	= tango_set_affinity,
	.irq_compose_msi_msg	= tango_compose_msi_msg,
};

static void msi_ack(struct irq_data *d)
{
	irq_chip_ack_parent(d);
}

static void msi_mask(struct irq_data *d)
{
	pci_msi_mask_irq(d);
	irq_chip_mask_parent(d);
}

static void msi_unmask(struct irq_data *d)
{
	pci_msi_unmask_irq(d);
	irq_chip_unmask_parent(d);
}

static struct irq_chip msi_chip = {
	.name = "MSI",
	.irq_ack = msi_ack,
	.irq_mask = msi_mask,
	.irq_unmask = msi_unmask,
};

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

static int tango_irq_domain_alloc(struct irq_domain *dom, unsigned int virq,
				  unsigned int nr_irqs, void *args)
{
	struct tango_pcie *pcie = dom->host_data;
	unsigned long flags;
	int pos;

	spin_lock_irqsave(&pcie->used_msi_lock, flags);
	pos = find_first_zero_bit(pcie->used_msi, MSI_MAX);
	if (pos >= MSI_MAX) {
		spin_unlock_irqrestore(&pcie->used_msi_lock, flags);
		return -ENOSPC;
	}
	__set_bit(pos, pcie->used_msi);
	spin_unlock_irqrestore(&pcie->used_msi_lock, flags);
	irq_domain_set_info(dom, virq, pos, &tango_chip,
			pcie, handle_edge_irq, NULL, NULL);

	return 0;
}

static void tango_irq_domain_free(struct irq_domain *dom, unsigned int virq,
				  unsigned int nr_irqs)
{
	unsigned long flags;
	struct irq_data *d = irq_domain_get_irq_data(dom, virq);
	struct tango_pcie *pcie = d->chip_data;

	spin_lock_irqsave(&pcie->used_msi_lock, flags);
	__clear_bit(d->hwirq, pcie->used_msi);
	spin_unlock_irqrestore(&pcie->used_msi_lock, flags);
}

static const struct irq_domain_ops dom_ops = {
	.alloc	= tango_irq_domain_alloc,
	.free	= tango_irq_domain_free,
};

static int smp8759_config_read(struct pci_bus *bus, unsigned int devfn,
			       int where, int size, u32 *val)
{
	struct pci_config_window *cfg = bus->sysdata;
	struct tango_pcie *pcie = dev_get_drvdata(cfg->parent);
	int ret;

	/* Reads in configuration space outside devfn 0 return garbage */
	if (devfn != 0)
		return PCIBIOS_FUNC_NOT_SUPPORTED;

	/*
	 * PCI config and MMIO accesses are muxed.  Linux doesn't have a
	 * mutual exclusion mechanism for config vs. MMIO accesses, so
	 * concurrent accesses may cause corruption.
	 */
	writel_relaxed(1, pcie->base + SMP8759_MUX);
	ret = pci_generic_config_read(bus, devfn, where, size, val);
	writel_relaxed(0, pcie->base + SMP8759_MUX);

	return ret;
}

static int smp8759_config_write(struct pci_bus *bus, unsigned int devfn,
				int where, int size, u32 val)
{
	struct pci_config_window *cfg = bus->sysdata;
	struct tango_pcie *pcie = dev_get_drvdata(cfg->parent);
	int ret;

	writel_relaxed(1, pcie->base + SMP8759_MUX);
	ret = pci_generic_config_write(bus, devfn, where, size, val);
	writel_relaxed(0, pcie->base + SMP8759_MUX);

	return ret;
}

static const struct pci_ecam_ops smp8759_ecam_ops = {
	.bus_shift	= 20,
	.pci_ops	= {
		.map_bus	= pci_ecam_map_bus,
		.read		= smp8759_config_read,
		.write		= smp8759_config_write,
	}
};

static int tango_pcie_link_up(struct tango_pcie *pcie)
{
	void __iomem *test_out = pcie->base + SMP8759_TEST_OUT;
	int i;

	writel_relaxed(16, test_out);
	for (i = 0; i < 10; ++i) {
		u32 ltssm_state = readl_relaxed(test_out) >> 8;
		if ((ltssm_state & 0x1f) == 0xf) /* L0 */
			return 1;
		usleep_range(3000, 4000);
	}

	return 0;
}

static int tango_pcie_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct tango_pcie *pcie;
	struct resource *res;
	struct fwnode_handle *fwnode = of_node_to_fwnode(dev->of_node);
	struct irq_domain *msi_dom, *irq_dom;
	struct of_pci_range_parser parser;
	struct of_pci_range range;
	int virq, offset;

	dev_warn(dev, "simultaneous PCI config and MMIO accesses may cause data corruption\n");
	add_taint(TAINT_CRAP, LOCKDEP_STILL_OK);

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

	res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
	pcie->base = devm_ioremap_resource(dev, res);
	if (IS_ERR(pcie->base))
		return PTR_ERR(pcie->base);

	platform_set_drvdata(pdev, pcie);

	if (!tango_pcie_link_up(pcie))
		return -ENODEV;

	if (of_pci_dma_range_parser_init(&parser, dev->of_node) < 0)
		return -ENOENT;

	if (of_pci_range_parser_one(&parser, &range) == NULL)
		return -ENOENT;

	range.pci_addr += range.size;
	pcie->msi_doorbell = range.pci_addr + res->start + SMP8759_DOORBELL;

	for (offset = 0; offset < MSI_MAX / 8; offset += 4)
		writel_relaxed(0, pcie->base + SMP8759_ENABLE + offset);

	virq = platform_get_irq(pdev, 1);
	if (virq < 0) {
		dev_err(dev, "Failed to map IRQ\n");
		return virq;
	}

	irq_dom = irq_domain_create_linear(fwnode, MSI_MAX, &dom_ops, pcie);
	if (!irq_dom) {
		dev_err(dev, "Failed to create IRQ domain\n");
		return -ENOMEM;
	}

	msi_dom = pci_msi_create_irq_domain(fwnode, &msi_dom_info, irq_dom);
	if (!msi_dom) {
		dev_err(dev, "Failed to create MSI domain\n");
		irq_domain_remove(irq_dom);
		return -ENOMEM;
	}

	pcie->dom = irq_dom;
	spin_lock_init(&pcie->used_msi_lock);
	irq_set_chained_handler_and_data(virq, tango_msi_isr, pcie);

	return pci_host_common_probe(pdev);
}

static const struct of_device_id tango_pcie_ids[] = {
	{
		.compatible = "sigma,smp8759-pcie",
		.data = &smp8759_ecam_ops,
	},
	{ },
};

static struct platform_driver tango_pcie_driver = {
	.probe	= tango_pcie_probe,
	.driver	= {
		.name = KBUILD_MODNAME,
		.of_match_table = tango_pcie_ids,
		.suppress_bind_attrs = true,
	},
};
builtin_platform_driver(tango_pcie_driver);

/*
 * The root complex advertises the wrong device class.
 * Header Type 1 is for PCI-to-PCI bridges.
 */
static void tango_fixup_class(struct pci_dev *dev)
{
	dev->class = PCI_CLASS_BRIDGE_PCI << 8;
}
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SIGMA, 0x0024, tango_fixup_class);
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SIGMA, 0x0028, tango_fixup_class);

/*
 * The root complex exposes a "fake" BAR, which is used to filter
 * bus-to-system accesses.  Only accesses within the range defined by this
 * BAR are forwarded to the host, others are ignored.
 *
 * By default, the DMA framework expects an identity mapping, and DRAM0 is
 * mapped at 0x80000000.
 */
static void tango_fixup_bar(struct pci_dev *dev)
{
	dev->non_compliant_bars = true;
	pci_write_config_dword(dev, PCI_BASE_ADDRESS_0, 0x80000000);
}
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SIGMA, 0x0024, tango_fixup_bar);
DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SIGMA, 0x0028, tango_fixup_bar);