On Mon, Aug 21, 2017 at 08:29:06PM +0100, Ard Biesheuvel wrote:

Most drivers that currently exist for the Synopsys Designware PCIe
controller in RC mode hardcode the relation with the embedded MSI
controller. This makes it more difficult than necessary to use a
generic driver to drive the RC, which is especially unfortunate
in cases where the firmware already configures the RC to the extent
that it can be driven by the generic ECAM driver. It also makes it
impossible to use an existing driver but use another IP block for
MSI support, i.e., a GICv2m or GICv3-ITS.

So add a separate driver for the MSI part, which can be referenced
from the DT node describing the RC via its msi-parent property.

Signed-off-by: Ard Biesheuvel <redacted>

+static int dw_pcie_msi_probe(struct platform_device *pdev)
+{
+	struct fwnode_handle *fwnode = of_node_to_fwnode(pdev->dev.of_node);
+	struct device *dev = &pdev->dev;
+	struct dw_pcie_msi *dw_msi;
+	struct resource *res;
+
+	dw_msi = devm_kzalloc(dev, sizeof(*dw_msi), GFP_KERNEL);
+	if (!dw_msi)
+		return -ENOMEM;
+
+	/* get the control register and map it */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	dw_msi->regbase = devm_ioremap_resource(dev, res);
+	if (IS_ERR(dw_msi->regbase))
+		return PTR_ERR(dw_msi->regbase);
+
+	/* get the wired interrupt that gets raised when we receive an MSI */
+	dw_msi->irq = platform_get_irq(pdev, 0);
+	if (dw_msi->irq <= 0) {
+		pr_err("Failed to map IRQ\n");

dev_err()

I'm not sure "failed to *map* IRQ" is the most informative text.
Other callers often use some variant of "failed to get IRQ" or "no IRQ
resource found".

+		return -ENXIO;
+	}
+
+	dw_msi->irqd = irq_domain_create_linear(fwnode, MAX_MSI_IRQS,
+						&irq_dom_ops, dw_msi);
+	if (!dw_msi->irqd) {
+		dev_err(dev, "Failed to create IRQ domain\n");
+		return -ENOMEM;