1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * pci.c -- basic PCI support code
4 *
5 * (C) Copyright 2011, Greg Ungerer <gerg@uclinux.org>
6 */
7
8 #include <linux/kernel.h>
9 #include <linux/types.h>
10 #include <linux/mm.h>
11 #include <linux/init.h>
12 #include <linux/pci.h>
13
14 /*
15 * From arch/i386/kernel/pci-i386.c:
16 *
17 * We need to avoid collisions with `mirrored' VGA ports
18 * and other strange ISA hardware, so we always want the
19 * addresses to be allocated in the 0x000-0x0ff region
20 * modulo 0x400.
21 *
22 * Why? Because some silly external IO cards only decode
23 * the low 10 bits of the IO address. The 0x00-0xff region
24 * is reserved for motherboard devices that decode all 16
25 * bits, so it's ok to allocate at, say, 0x2800-0x28ff,
26 * but we want to try to avoid allocating at 0x2900-0x2bff
27 * which might be mirrored at 0x0100-0x03ff..
28 */
29 resource_size_t pcibios_align_resource(void *data, const struct resource *res,
30 resource_size_t size, resource_size_t align)
31 {
32 resource_size_t start = res->start;
33
34 if ((res->flags & IORESOURCE_IO) && (start & 0x300))
35 start = (start + 0x3ff) & ~0x3ff;
36
37 start = (start + align - 1) & ~(align - 1);
38
39 return start;
40 }
41
42 /*
43 * This is taken from the ARM code for this.
44 */
45 int pcibios_enable_device(struct pci_dev *dev, int mask)
46 {
47 struct resource *r;
48 u16 cmd, newcmd;
49 int idx;
50
51 pci_read_config_word(dev, PCI_COMMAND, &cmd);
52 newcmd = cmd;
53
54 for (idx = 0; idx < 6; idx++) {
55 /* Only set up the requested stuff */
56 if (!(mask & (1 << idx)))
57 continue;
58
59 r = dev->resource + idx;
60 if (!r->start && r->end) {
61 pr_err("PCI: Device %s not available because of resource collisions\n",
62 pci_name(dev));
63 return -EINVAL;
64 }
65 if (r->flags & IORESOURCE_IO)
66 newcmd |= PCI_COMMAND_IO;
67 if (r->flags & IORESOURCE_MEM)
68 newcmd |= PCI_COMMAND_MEMORY;
69 }
70
71 /*
72 * Bridges (eg, cardbus bridges) need to be fully enabled
73 */
74 if ((dev->class >> 16) == PCI_BASE_CLASS_BRIDGE)
75 newcmd |= PCI_COMMAND_IO | PCI_COMMAND_MEMORY;
76
77
78 if (newcmd != cmd) {
79 pr_info("PCI: enabling device %s (0x%04x -> 0x%04x)\n",
80 pci_name(dev), cmd, newcmd);
81 pci_write_config_word(dev, PCI_COMMAND, newcmd);
82 }
83 return 0;
84 }
85
86 void pcibios_fixup_bus(struct pci_bus *bus)
87 {
88 struct pci_dev *dev;
89
90 list_for_each_entry(dev, &bus->devices, bus_list) {
91 pci_write_config_byte(dev, PCI_CACHE_LINE_SIZE, 8);
92 pci_write_config_byte(dev, PCI_LATENCY_TIMER, 32);
93 }
94 }
95
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