1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * PCI-related functions used by the EFI stub on multiple
4 * architectures.
5 *
6 * Copyright 2019 Google, LLC
7 */
8
9 #include <linux/efi.h>
10 #include <linux/pci.h>
11
12 #include <asm/efi.h>
13
14 #include "efistub.h"
15
efi_pci_disable_bridge_busmaster(void)16 void efi_pci_disable_bridge_busmaster(void)
17 {
18 efi_guid_t pci_proto = EFI_PCI_IO_PROTOCOL_GUID;
19 unsigned long pci_handle_size = 0;
20 efi_handle_t *pci_handle = NULL;
21 efi_handle_t handle;
22 efi_status_t status;
23 u16 class, command;
24 int i;
25
26 status = efi_bs_call(locate_handle, EFI_LOCATE_BY_PROTOCOL, &pci_proto,
27 NULL, &pci_handle_size, NULL);
28
29 if (status != EFI_BUFFER_TOO_SMALL) {
30 if (status != EFI_SUCCESS && status != EFI_NOT_FOUND)
31 efi_err("Failed to locate PCI I/O handles'\n");
32 return;
33 }
34
35 status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, pci_handle_size,
36 (void **)&pci_handle);
37 if (status != EFI_SUCCESS) {
38 efi_err("Failed to allocate memory for 'pci_handle'\n");
39 return;
40 }
41
42 status = efi_bs_call(locate_handle, EFI_LOCATE_BY_PROTOCOL, &pci_proto,
43 NULL, &pci_handle_size, pci_handle);
44 if (status != EFI_SUCCESS) {
45 efi_err("Failed to locate PCI I/O handles'\n");
46 goto free_handle;
47 }
48
49 for_each_efi_handle(handle, pci_handle, pci_handle_size, i) {
50 efi_pci_io_protocol_t *pci;
51 unsigned long segment_nr, bus_nr, device_nr, func_nr;
52
53 status = efi_bs_call(handle_protocol, handle, &pci_proto,
54 (void **)&pci);
55 if (status != EFI_SUCCESS)
56 continue;
57
58 /*
59 * Disregard devices living on bus 0 - these are not behind a
60 * bridge so no point in disconnecting them from their drivers.
61 */
62 status = efi_call_proto(pci, get_location, &segment_nr, &bus_nr,
63 &device_nr, &func_nr);
64 if (status != EFI_SUCCESS || bus_nr == 0)
65 continue;
66
67 /*
68 * Don't disconnect VGA controllers so we don't risk losing
69 * access to the framebuffer. Drivers for true PCIe graphics
70 * controllers that are behind a PCIe root port do not use
71 * DMA to implement the GOP framebuffer anyway [although they
72 * may use it in their implementation of Gop->Blt()], and so
73 * disabling DMA in the PCI bridge should not interfere with
74 * normal operation of the device.
75 */
76 status = efi_call_proto(pci, pci.read, EfiPciIoWidthUint16,
77 PCI_CLASS_DEVICE, 1, &class);
78 if (status != EFI_SUCCESS || class == PCI_CLASS_DISPLAY_VGA)
79 continue;
80
81 /* Disconnect this handle from all its drivers */
82 efi_bs_call(disconnect_controller, handle, NULL, NULL);
83 }
84
85 for_each_efi_handle(handle, pci_handle, pci_handle_size, i) {
86 efi_pci_io_protocol_t *pci;
87
88 status = efi_bs_call(handle_protocol, handle, &pci_proto,
89 (void **)&pci);
90 if (status != EFI_SUCCESS || !pci)
91 continue;
92
93 status = efi_call_proto(pci, pci.read, EfiPciIoWidthUint16,
94 PCI_CLASS_DEVICE, 1, &class);
95
96 if (status != EFI_SUCCESS || class != PCI_CLASS_BRIDGE_PCI)
97 continue;
98
99 /* Disable busmastering */
100 status = efi_call_proto(pci, pci.read, EfiPciIoWidthUint16,
101 PCI_COMMAND, 1, &command);
102 if (status != EFI_SUCCESS || !(command & PCI_COMMAND_MASTER))
103 continue;
104
105 command &= ~PCI_COMMAND_MASTER;
106 status = efi_call_proto(pci, pci.write, EfiPciIoWidthUint16,
107 PCI_COMMAND, 1, &command);
108 if (status != EFI_SUCCESS)
109 efi_err("Failed to disable PCI busmastering\n");
110 }
111
112 free_handle:
113 efi_bs_call(free_pool, pci_handle);
114 }
115