PCI: dwc: Handle MSIs routed to multiple GIC interrupts

On some Qualcomm platforms each group of 32 MSI vectors is routed to a
separate GIC interrupt. Implement support for such configurations by
parsing "msi0" ... "msiX" interrupts and attaching them to the chained
handler.

Note that if DT doesn't list an array of MSI interrupts and uses a single
"msi" IRQ, the driver will limit the number of supported MSI vectors to 32.

Link: https://lore.kernel.org/r/20220707134733.2436629-5-dmitry.baryshkov@linaro.orgSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Johan Hovold <johan+linaro@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

drivers/pci/controller/dwc/pcie-designware-host.c

@@ -291,6 +291,46 @@ static void dw_pcie_msi_init(struct dw_pcie_rp *pp)
 	dw_pcie_writel_dbi(pci, PCIE_MSI_ADDR_HI, upper_32_bits(msi_target));
 }
 
+static int dw_pcie_parse_split_msi_irq(struct dw_pcie_rp *pp)
+{
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+	struct device *dev = pci->dev;
+	struct platform_device *pdev = to_platform_device(dev);
+	u32 ctrl, max_vectors;
+	int irq;
+
+	/* Parse any "msiX" IRQs described in the devicetree */
+	for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++) {
+		char msi_name[] = "msiX";
+
+		msi_name[3] = '0' + ctrl;
+		irq = platform_get_irq_byname_optional(pdev, msi_name);
+		if (irq == -ENXIO)
+			break;
+		if (irq < 0)
+			return dev_err_probe(dev, irq,
+					     "Failed to parse MSI IRQ '%s'\n",
+					     msi_name);
+
+		pp->msi_irq[ctrl] = irq;
+	}
+
+	/* If no "msiX" IRQs, caller should fallback to "msi" IRQ */
+	if (ctrl == 0)
+		return -ENXIO;
+
+	max_vectors = ctrl * MAX_MSI_IRQS_PER_CTRL;
+	if (pp->num_vectors > max_vectors) {
+		dev_warn(dev, "Exceeding number of MSI vectors, limiting to %u\n",
+			 max_vectors);
+		pp->num_vectors = max_vectors;
+	}
+	if (!pp->num_vectors)
+		pp->num_vectors = max_vectors;
+
+	return 0;
+}
+
 static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
@@ -299,10 +339,19 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
 	int ret;
 	u32 ctrl, num_ctrls;
 
-	num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
-	for (ctrl = 0; ctrl < num_ctrls; ctrl++)
+	for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++)
 		pp->irq_mask[ctrl] = ~0;
 
+	if (!pp->msi_irq[0]) {
+		ret = dw_pcie_parse_split_msi_irq(pp);
+		if (ret < 0 && ret != -ENXIO)
+			return ret;
+	}
+
+	if (!pp->num_vectors)
+		pp->num_vectors = MSI_DEF_NUM_VECTORS;
+	num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
+
 	if (!pp->msi_irq[0]) {
 		pp->msi_irq[0] = platform_get_irq_byname_optional(pdev, "msi");
 		if (pp->msi_irq[0] < 0) {
@@ -312,6 +361,8 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
 		}
 	}
 
+	dev_dbg(dev, "Using %d MSI vectors\n", pp->num_vectors);
+
 	pp->msi_irq_chip = &dw_pci_msi_bottom_irq_chip;
 
 	ret = dw_pcie_allocate_domains(pp);
@@ -410,7 +461,11 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
 				     of_property_read_bool(np, "msi-parent") ||
 				     of_property_read_bool(np, "msi-map"));
 
-		if (!pp->num_vectors) {
+		/*
+		 * For the has_msi_ctrl case the default assignment is handled
+		 * in the dw_pcie_msi_host_init().
+		 */
+		if (!pp->has_msi_ctrl && !pp->num_vectors) {
 			pp->num_vectors = MSI_DEF_NUM_VECTORS;
 		} else if (pp->num_vectors > MAX_MSI_IRQS) {
 			dev_err(dev, "Invalid number of vectors\n");