[PATCH v3 1/2] PCI: Add tango MSI controller support

[Marc Gonzalez]

The MSI controller in Tango supports 256 message-signaled interrupts,
and a single doorbell address.

Signed-off-by: Marc Gonzalez <marc_gonzalez at sigmadesigns.com>
---
Changes since v0.2
- Support 256 MSIs instead of only 32
- Use spinlock_t instead of struct mutex
- Add MSI_FLAG_PCI_MSIX flag

IRQs are acked in tango_msi_isr because handle_simple_irq leaves
ack, clear, mask and unmask up to the driver. For the same reason,
interrupt enable mask is updated from tango_irq_domain_alloc/free.
---
 drivers/pci/host/pcie-tango.c | 194 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 194 insertions(+)

diff --git a/drivers/pci/host/pcie-tango.c b/drivers/pci/host/pcie-tango.c
new file mode 100644
index 000000000000..e88850983a1d
--- /dev/null
+++ b/drivers/pci/host/pcie-tango.c
@@ -0,0 +1,194 @@
+#include <linux/module.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/irqdomain.h>
+#include <linux/pci-ecam.h>
+#include <linux/msi.h>
+
+#define MSI_MAX 256
+
+struct tango_pcie {
+	DECLARE_BITMAP(bitmap, MSI_MAX);
+	spinlock_t lock;
+	void __iomem *mux;
+	void __iomem *msi_status;
+	void __iomem *msi_mask;
+	phys_addr_t msi_doorbell;
+	struct irq_domain *irq_domain;
+	struct irq_domain *msi_domain;
+	int irq;
+};
+
+/*** MSI CONTROLLER SUPPORT ***/
+
+static void dispatch(struct tango_pcie *pcie, unsigned long status, int base)
+{
+	unsigned int pos, virq;
+
+	for_each_set_bit(pos, &status, 32) {
+		virq = irq_find_mapping(pcie->irq_domain, base + pos);
+		generic_handle_irq(virq);
+	}
+}
+
+static void tango_msi_isr(struct irq_desc *desc)
+{
+	u32 status;
+	struct irq_chip *chip = irq_desc_get_chip(desc);
+	struct tango_pcie *pcie = irq_desc_get_handler_data(desc);
+	unsigned int base, offset, pos = 0;
+
+	chained_irq_enter(chip, desc);
+
+	while ((pos = find_next_bit(pcie->bitmap, MSI_MAX, pos)) < MSI_MAX) {
+		base = round_down(pos, 32);
+		offset = (pos / 32) * 4;
+		status = readl_relaxed(pcie->msi_status + offset);
+		writel_relaxed(status, pcie->msi_status + offset);
+		dispatch(pcie, status, base);
+		pos = base + 32;
+	}
+
+	chained_irq_exit(chip, desc);
+}
+
+static struct irq_chip tango_msi_irq_chip = {
+	.name = "MSI",
+	.irq_mask = pci_msi_mask_irq,
+	.irq_unmask = pci_msi_unmask_irq,
+};
+
+#define USE_DEF_OPS (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS)
+
+static struct msi_domain_info msi_domain_info = {
+	.flags	= USE_DEF_OPS | MSI_FLAG_PCI_MSIX,
+	.chip	= &tango_msi_irq_chip,
+};
+
+static void tango_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
+{
+	struct tango_pcie *pcie = irq_data_get_irq_chip_data(data);
+
+	msg->address_lo = lower_32_bits(pcie->msi_doorbell);
+	msg->address_hi = upper_32_bits(pcie->msi_doorbell);
+	msg->data = data->hwirq;
+}
+
+static int tango_set_affinity(struct irq_data *irq_data,
+		const struct cpumask *mask, bool force)
+{
+	 return -EINVAL;
+}
+
+static struct irq_chip tango_msi_chip = {
+	.name			= "MSI",
+	.irq_compose_msi_msg	= tango_compose_msi_msg,
+	.irq_set_affinity	= tango_set_affinity,
+};
+
+static int find_free_msi(struct irq_domain *dom, unsigned int virq)
+{
+	u32 val;
+	struct tango_pcie *pcie = dom->host_data;
+	unsigned int offset, pos;
+
+	pos = find_first_zero_bit(pcie->bitmap, MSI_MAX);
+	if (pos >= MSI_MAX)
+		return -ENOSPC;
+
+	offset = (pos / 32) * 4;
+	val = readl_relaxed(pcie->msi_mask + offset);
+	writel_relaxed(val | BIT(pos % 32), pcie->msi_mask + offset);
+	__set_bit(pos, pcie->bitmap);
+
+	irq_domain_set_info(dom, virq, pos, &tango_msi_chip,
+			dom->host_data, handle_simple_irq, NULL, NULL);
+
+	return 0;
+}
+
+static int tango_irq_domain_alloc(struct irq_domain *dom,
+		unsigned int virq, unsigned int nr_irqs, void *args)
+{
+	int err;
+	struct tango_pcie *pcie = dom->host_data;
+
+	spin_lock(&pcie->lock);
+	err = find_free_msi(dom, virq);
+	spin_unlock(&pcie->lock);
+
+	return err;
+}
+
+static void tango_irq_domain_free(struct irq_domain *dom,
+		unsigned int virq, unsigned int nr_irqs)
+{
+	u32 val;
+	struct irq_data *d = irq_domain_get_irq_data(dom, virq);
+	struct tango_pcie *pcie = irq_data_get_irq_chip_data(d);
+	unsigned int offset, pos = d->hwirq;
+
+	spin_lock(&pcie->lock);
+
+	offset = (pos / 32) * 4;
+	val = readl_relaxed(pcie->msi_mask + offset);
+	writel_relaxed(val & ~BIT(pos % 32), pcie->msi_mask + offset);
+	__clear_bit(pos, pcie->bitmap);
+
+	spin_unlock(&pcie->lock);
+}
+
+static const struct irq_domain_ops msi_dom_ops = {
+	.alloc	= tango_irq_domain_alloc,
+	.free	= tango_irq_domain_free,
+};
+
+static int tango_msi_remove(struct platform_device *pdev)
+{
+	struct tango_pcie *msi = platform_get_drvdata(pdev);
+
+	irq_set_chained_handler_and_data(msi->irq, NULL, NULL);
+	irq_domain_remove(msi->msi_domain);
+	irq_domain_remove(msi->irq_domain);
+
+	return 0;
+}
+
+static int tango_msi_probe(struct platform_device *pdev, struct tango_pcie *pcie)
+{
+	int i, virq;
+	struct fwnode_handle *fwnode = of_node_to_fwnode(pdev->dev.of_node);
+	struct irq_domain *msi_dom, *irq_dom;
+
+	spin_lock_init(&pcie->lock);
+
+	for (i = 0; i < MSI_MAX / 32; ++i)
+		writel_relaxed(0, pcie->msi_mask + i * 4);
+
+	irq_dom = irq_domain_create_linear(fwnode, MSI_MAX, &msi_dom_ops, pcie);
+	if (!irq_dom) {
+		pr_err("Failed to create IRQ domain\n");
+		return -ENOMEM;
+	}
+
+	msi_dom = pci_msi_create_irq_domain(fwnode, &msi_domain_info, irq_dom);
+	if (!msi_dom) {
+		pr_err("Failed to create MSI domain\n");
+		irq_domain_remove(irq_dom);
+		return -ENOMEM;
+	}
+
+	virq = platform_get_irq(pdev, 1);
+	if (virq <= 0) {
+		pr_err("Failed to map IRQ\n");
+		irq_domain_remove(msi_dom);
+		irq_domain_remove(irq_dom);
+		return -ENXIO;
+	}
+
+	pcie->irq_domain = irq_dom;
+	pcie->msi_domain = msi_dom;
+	pcie->irq = virq;
+	irq_set_chained_handler_and_data(virq, tango_msi_isr, pcie);
+
+	return 0;
+}
-- 
2.11.0