PCI: dwc: Fix MSI msi_msg DMA mapping

As of 07940c36 ("PCI: dwc: Fix MSI page leakage in suspend/resume"),
the PCIe designware host driver has been using the driver data allocation
for the msi_msg DMA mapping which can result in a DMA_MAPPING_ERROR due to
the DMA overflow check in dma_direct_map_page() when the address is greater
than 32 bits (reported in [1]). The commit was trying to address a memory
leak on suspend/resume by moving the MSI mapping to dw_pcie_host_init(),
but subsequently dropped the page allocation thinking it wasn't needed.

To fix the DMA mapping issue as well as make msi_msg DMA'able, switch back
to allocating a 32-bit page for the msi_msg. To avoid the suspend/resume
leak, allocate the page in dw_pcie_host_init() since that shouldn't be
called during suspend/resume.

[1] https://lore.kernel.org/all/Yo0soniFborDl7+C@google.com/Signed-off-by: Will McVicker <willmcvicker@google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rob Herring <robh@kernel.org>

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

@@ -267,8 +267,9 @@ static void dw_pcie_free_msi(struct dw_pcie_rp *pp)
 		struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 		struct device *dev = pci->dev;
 
-		dma_unmap_single_attrs(dev, pp->msi_data, sizeof(pp->msi_msg),
-				       DMA_FROM_DEVICE, DMA_ATTR_SKIP_CPU_SYNC);
+		dma_unmap_page(dev, pp->msi_data, PAGE_SIZE, DMA_FROM_DEVICE);
+		if (pp->msi_page)
+			__free_page(pp->msi_page);
 	}
 }
 
@@ -395,13 +396,14 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
 			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");
 
-			pp->msi_data = dma_map_single_attrs(dev, &pp->msi_msg,
-						      sizeof(pp->msi_msg),
-						      DMA_FROM_DEVICE,
-						      DMA_ATTR_SKIP_CPU_SYNC);
+			pp->msi_page = alloc_page(GFP_DMA32);
+			pp->msi_data = dma_map_page(dev, pp->msi_page, 0,
+						    PAGE_SIZE, DMA_FROM_DEVICE);
 			ret = dma_mapping_error(dev, pp->msi_data);
 			if (ret) {
 				dev_err(pci->dev, "Failed to map MSI data\n");
+				__free_page(pp->msi_page);
+				pp->msi_page = NULL;
 				pp->msi_data = 0;
 				goto err_free_msi;
 			}

drivers/pci/controller/dwc/pcie-designware.h

@@ -203,8 +203,8 @@ struct dw_pcie_rp {
 	int			msi_irq;
 	struct irq_domain	*irq_domain;
 	struct irq_domain	*msi_domain;
-	u16			msi_msg;
 	dma_addr_t		msi_data;
+	struct page		*msi_page;
 	struct irq_chip		*msi_irq_chip;
 	u32			num_vectors;
 	u32			irq_mask[MAX_MSI_CTRLS];