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
16void 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
112free_handle:
113	efi_bs_call(free_pool, pci_handle);
114}
115