x86/PCI: Allow DMA ops specific to a PCI domain

The Intel Volume Management Device (VMD) is a PCIe endpoint that acts as a
host bridge to another PCI domain. When devices below the VMD perform DMA,
the VMD replaces their DMA source IDs with its own source ID. Therefore,
those devices require special DMA ops.

Add interfaces to allow the VMD driver to set up dma_ops for the devices
below it.

[bhelgaas: remove "extern", add "static", changelog]
Signed-off-by: Keith Busch <[e-mail]>
Signed-off-by: Bjorn Helgaas <[e-mail]>

arch/x86/include/asm/device.h

···
 #endif
 };
 
+#if defined(CONFIG_X86_DEV_DMA_OPS) && defined(CONFIG_PCI_DOMAINS)
+struct dma_domain {
+	struct list_head node;
+	struct dma_map_ops *dma_ops;
+	int domain_nr;
+};
+void add_dma_domain(struct dma_domain *domain);
+void del_dma_domain(struct dma_domain *domain);
+#endif
+
 struct pdev_archdata {
 };
 

arch/x86/pci/common.c

···
 	return (pci_probe & PCI_ASSIGN_ALL_BUSSES) ? 1 : 0;
 }
 
+#if defined(CONFIG_X86_DEV_DMA_OPS) && defined(CONFIG_PCI_DOMAINS)
+static LIST_HEAD(dma_domain_list);
+static DEFINE_SPINLOCK(dma_domain_list_lock);
+
+void add_dma_domain(struct dma_domain *domain)
+{
+	spin_lock(&dma_domain_list_lock);
+	list_add(&domain->node, &dma_domain_list);
+	spin_unlock(&dma_domain_list_lock);
+}
+EXPORT_SYMBOL_GPL(add_dma_domain);
+
+void del_dma_domain(struct dma_domain *domain)
+{
+	spin_lock(&dma_domain_list_lock);
+	list_del(&domain->node);
+	spin_unlock(&dma_domain_list_lock);
+}
+EXPORT_SYMBOL_GPL(del_dma_domain);
+
+static void set_dma_domain_ops(struct pci_dev *pdev)
+{
+	struct dma_domain *domain;
+
+	spin_lock(&dma_domain_list_lock);
+	list_for_each_entry(domain, &dma_domain_list, node) {
+		if (pci_domain_nr(pdev->bus) == domain->domain_nr) {
+			pdev->dev.archdata.dma_ops = domain->dma_ops;
+			break;
+		}
+	}
+	spin_unlock(&dma_domain_list_lock);
+}
+#else
+static void set_dma_domain_ops(struct pci_dev *pdev) {}
+#endif
+
 int pcibios_add_device(struct pci_dev *dev)
 {
 	struct setup_data *data;
···
 		pa_data = data->next;
 		iounmap(data);
 	}
+	set_dma_domain_ops(dev);
 	return 0;
 }