1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include <linux/pci.h>
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>
10 
11 #include <asm/iommu.h>
12 #include <asm/swiotlb.h>
13 #include <asm/dma.h>
14 #include <asm/xen/swiotlb-xen.h>
15 #include <asm/iommu_table.h>
16 
17 int swiotlb __read_mostly;
18 
19 /*
20  * pci_swiotlb_detect_override - set swiotlb to 1 if necessary
21  *
22  * This returns non-zero if we are forced to use swiotlb (by the boot
23  * option).
24  */
pci_swiotlb_detect_override(void)25 int __init pci_swiotlb_detect_override(void)
26 {
27 	if (swiotlb_force == SWIOTLB_FORCE)
28 		swiotlb = 1;
29 
30 	return swiotlb;
31 }
32 IOMMU_INIT_FINISH(pci_swiotlb_detect_override,
33 		  pci_xen_swiotlb_detect,
34 		  pci_swiotlb_init,
35 		  pci_swiotlb_late_init);
36 
37 /*
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.
40  */
pci_swiotlb_detect_4gb(void)41 int __init pci_swiotlb_detect_4gb(void)
42 {
43 	/* don't initialize swiotlb if iommu=off (no_iommu=1) */
44 	if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN)
45 		swiotlb = 1;
46 
47 	/*
48 	 * Set swiotlb to 1 so that bounce buffers are allocated and used for
49 	 * devices that can't support DMA to encrypted memory.
50 	 */
51 	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
52 		swiotlb = 1;
53 
54 	return swiotlb;
55 }
56 IOMMU_INIT(pci_swiotlb_detect_4gb,
57 	   pci_swiotlb_detect_override,
58 	   pci_swiotlb_init,
59 	   pci_swiotlb_late_init);
60 
pci_swiotlb_init(void)61 void __init pci_swiotlb_init(void)
62 {
63 	if (swiotlb)
64 		swiotlb_init(0);
65 }
66 
pci_swiotlb_late_init(void)67 void __init pci_swiotlb_late_init(void)
68 {
69 	/* An IOMMU turned us off. */
70 	if (!swiotlb)
71 		swiotlb_exit();
72 	else {
73 		printk(KERN_INFO "PCI-DMA: "
74 		       "Using software bounce buffering for IO (SWIOTLB)\n");
75 		swiotlb_print_info();
76 	}
77 }
78