PCI: dwc: Drop dependency on ZONE_DMA32

Re-work the msi_msg DMA allocation logic to use dmam_alloc_coherent() which
uses the coherent DMA mask to try to return an allocation within the DMA
mask limits. With that, we now can drop the msi_page parameter in struct
dw_pcie_rp. This allows kernel configurations that disable ZONE_DMA32 to
continue supporting a 32-bit DMA mask. Without this patch, the PCIe host
device will fail to probe when ZONE_DMA32 is disabled.

Link: https://lore.kernel.org/r/20220825235404.4132818-2-willmcvicker@google.com
Fixes: 35797e6 ("PCI: dwc: Fix MSI msi_msg DMA mapping")
Reported-by: Isaac J. Manjarres <isaacmanjarres@google.com>
Signed-off-by: Will McVicker <willmcvicker@google.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Jingoo Han <jingoohan1@gmail.com>

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

@@ -267,15 +267,6 @@ static void dw_pcie_free_msi(struct dw_pcie_rp *pp)
 
 	irq_domain_remove(pp->msi_domain);
 	irq_domain_remove(pp->irq_domain);
-
-	if (pp->msi_data) {
-		struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
-		struct device *dev = pci->dev;
-
-		dma_unmap_page(dev, pp->msi_data, PAGE_SIZE, DMA_FROM_DEVICE);
-		if (pp->msi_page)
-			__free_page(pp->msi_page);
-	}
 }
 
 static void dw_pcie_msi_init(struct dw_pcie_rp *pp)
@@ -336,6 +327,7 @@ static int dw_pcie_msi_host_init(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);
+	u64 *msi_vaddr;
 	int ret;
 	u32 ctrl, num_ctrls;
 
@@ -375,22 +367,16 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
 						    dw_chained_msi_isr, pp);
 	}
 
-	ret = dma_set_mask(dev, DMA_BIT_MASK(32));
+	ret = dma_set_mask_and_coherent(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");
 
-	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;
+	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 ret;
+		return -ENOMEM;
 	}
 
 	return 0;

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

@@ -243,7 +243,6 @@ struct dw_pcie_rp {
 	struct irq_domain	*irq_domain;
 	struct irq_domain	*msi_domain;
 	dma_addr_t		msi_data;
-	struct page		*msi_page;
 	struct irq_chip		*msi_irq_chip;
 	u32			num_vectors;
 	u32			irq_mask[MAX_MSI_CTRLS];