PCI: dwc: Strengthen the MSI address allocation logic

There can be platforms that do not use/have 32-bit DMA addresses.
The current implementation of 32-bit IOVA allocation can fail for
such platforms, eventually leading to the probe failure.

Try to allocate a 32-bit msi_data. If this allocation fails,
attempt a 64-bit address allocation. Please note that if the
64-bit MSI address is allocated, then the EPs supporting 32-bit
MSI address only will not work.

Link: https://lore.kernel.org/linux-pci/[e-mail]
Tested-by: Will McVicker <[e-mail]>
Signed-off-by: Ajay Agarwal <[e-mail]>
Signed-off-by: Krzysztof Wilczyński <[e-mail]>
Reviewed-by: Manivannan Sadhasivam <[e-mail]>
Reviewed-by: Serge Semin <[e-mail]>
Reviewed-by: Will McVicker <[e-mail]>

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

···
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct device *dev = pci->dev;
 	struct platform_device *pdev = to_platform_device(dev);
-	u64 *msi_vaddr;
+	u64 *msi_vaddr = NULL;
 	int ret;
 	u32 ctrl, num_ctrls;
 
···
 	 * memory.
 	 */
 	ret = dma_set_coherent_mask(dev, DMA_BIT_MASK(32));
-	if (ret)
-		dev_warn(dev, "Failed to set DMA mask to 32-bit. Devices with only 32-bit MSI support may not work properly\n");
+	if (!ret)
+		msi_vaddr = dmam_alloc_coherent(dev, sizeof(u64), &pp->msi_data,
+						GFP_KERNEL);
 
-	msi_vaddr = dmam_alloc_coherent(dev, sizeof(u64), &pp->msi_data,
-					GFP_KERNEL);
 	if (!msi_vaddr) {
-		dev_err(dev, "Failed to alloc and map MSI data\n");
-		dw_pcie_free_msi(pp);
-		return -ENOMEM;
+		dev_warn(dev, "Failed to allocate 32-bit MSI address\n");
+		dma_set_coherent_mask(dev, DMA_BIT_MASK(64));
+		msi_vaddr = dmam_alloc_coherent(dev, sizeof(u64), &pp->msi_data,
+						GFP_KERNEL);
+		if (!msi_vaddr) {
+			dev_err(dev, "Failed to allocate MSI address\n");
+			dw_pcie_free_msi(pp);
+			return -ENOMEM;
+		}
 	}
 
 	return 0;