1 // SPDX-License-Identifier: GPL-2.0
4 #include <linux/cache.h>
5 #include <linux/init.h>
6 #include <linux/swiotlb.h>
7 #include <linux/memblock.h>
8 #include <linux/dma-direct.h>
9 #include <linux/cc_platform.h>
11 #include <asm/iommu.h>
12 #include <asm/swiotlb.h>
14 #include <asm/xen/swiotlb-xen.h>
15 #include <asm/iommu_table.h>
17 int swiotlb __read_mostly;
20 * pci_swiotlb_detect_override - set swiotlb to 1 if necessary
22 * This returns non-zero if we are forced to use swiotlb (by the boot
25 int __init pci_swiotlb_detect_override(void)
27 if (swiotlb_force == SWIOTLB_FORCE)
32 IOMMU_INIT_FINISH(pci_swiotlb_detect_override,
33 pci_xen_swiotlb_detect,
35 pci_swiotlb_late_init);
38 * If 4GB or more detected (and iommu=off not set) or if SME is active
39 * then set swiotlb to 1 and return 1.
41 int __init pci_swiotlb_detect_4gb(void)
43 /* don't initialize swiotlb if iommu=off (no_iommu=1) */
44 if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN)
48 * Set swiotlb to 1 so that bounce buffers are allocated and used for
49 * devices that can't support DMA to encrypted memory.
51 if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
56 IOMMU_INIT(pci_swiotlb_detect_4gb,
57 pci_swiotlb_detect_override,
59 pci_swiotlb_late_init);
61 void __init pci_swiotlb_init(void)
67 void __init pci_swiotlb_late_init(void)
69 /* An IOMMU turned us off. */
73 printk(KERN_INFO "PCI-DMA: "
74 "Using software bounce buffering for IO (SWIOTLB)\n");