Commit | Line | Data |
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e2b8785e AN |
1 | /* |
2 | * Thunderbolt Cactus Ridge driver - capabilities lookup | |
3 | * | |
4 | * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com> | |
5 | */ | |
6 | ||
7 | #include <linux/slab.h> | |
8 | #include <linux/errno.h> | |
9 | ||
10 | #include "tb.h" | |
11 | ||
12 | ||
13 | struct tb_cap_any { | |
14 | union { | |
15 | struct tb_cap_basic basic; | |
16 | struct tb_cap_extended_short extended_short; | |
17 | struct tb_cap_extended_long extended_long; | |
18 | }; | |
19 | } __packed; | |
20 | ||
21 | static bool tb_cap_is_basic(struct tb_cap_any *cap) | |
22 | { | |
23 | /* basic.cap is u8. This checks only the lower 8 bit of cap. */ | |
24 | return cap->basic.cap != 5; | |
25 | } | |
26 | ||
27 | static bool tb_cap_is_long(struct tb_cap_any *cap) | |
28 | { | |
29 | return !tb_cap_is_basic(cap) | |
30 | && cap->extended_short.next == 0 | |
31 | && cap->extended_short.length == 0; | |
32 | } | |
33 | ||
34 | static enum tb_cap tb_cap(struct tb_cap_any *cap) | |
35 | { | |
36 | if (tb_cap_is_basic(cap)) | |
37 | return cap->basic.cap; | |
38 | else | |
39 | /* extended_short/long have cap at the same offset. */ | |
40 | return cap->extended_short.cap; | |
41 | } | |
42 | ||
43 | static u32 tb_cap_next(struct tb_cap_any *cap, u32 offset) | |
44 | { | |
45 | int next; | |
46 | if (offset == 1) { | |
47 | /* | |
48 | * The first pointer is part of the switch header and always | |
49 | * a simple pointer. | |
50 | */ | |
51 | next = cap->basic.next; | |
52 | } else { | |
53 | /* | |
54 | * Somehow Intel decided to use 3 different types of capability | |
55 | * headers. It is not like anyone could have predicted that | |
56 | * single byte offsets are not enough... | |
57 | */ | |
58 | if (tb_cap_is_basic(cap)) | |
59 | next = cap->basic.next; | |
60 | else if (!tb_cap_is_long(cap)) | |
61 | next = cap->extended_short.next; | |
62 | else | |
63 | next = cap->extended_long.next; | |
64 | } | |
65 | /* | |
66 | * "Hey, we could terminate some capability lists with a null offset | |
67 | * and others with a pointer to the last element." - "Great idea!" | |
68 | */ | |
69 | if (next == offset) | |
70 | return 0; | |
71 | return next; | |
72 | } | |
73 | ||
74 | /** | |
75 | * tb_find_cap() - find a capability | |
76 | * | |
77 | * Return: Returns a positive offset if the capability was found and 0 if not. | |
78 | * Returns an error code on failure. | |
79 | */ | |
80 | int tb_find_cap(struct tb_port *port, enum tb_cfg_space space, enum tb_cap cap) | |
81 | { | |
82 | u32 offset = 1; | |
83 | struct tb_cap_any header; | |
84 | int res; | |
85 | int retries = 10; | |
86 | while (retries--) { | |
87 | res = tb_port_read(port, &header, space, offset, 1); | |
88 | if (res) { | |
89 | /* Intel needs some help with linked lists. */ | |
90 | if (space == TB_CFG_PORT && offset == 0xa | |
91 | && port->config.type == TB_TYPE_DP_HDMI_OUT) { | |
92 | offset = 0x39; | |
93 | continue; | |
94 | } | |
95 | return res; | |
96 | } | |
97 | if (offset != 1) { | |
98 | if (tb_cap(&header) == cap) | |
99 | return offset; | |
100 | if (tb_cap_is_long(&header)) { | |
101 | /* tb_cap_extended_long is 2 dwords */ | |
102 | res = tb_port_read(port, &header, space, | |
103 | offset, 2); | |
104 | if (res) | |
105 | return res; | |
106 | } | |
107 | } | |
108 | offset = tb_cap_next(&header, offset); | |
109 | if (!offset) | |
110 | return 0; | |
111 | } | |
112 | tb_port_WARN(port, | |
113 | "run out of retries while looking for cap %#x in config space %d, last offset: %#x\n", | |
114 | cap, space, offset); | |
115 | return -EIO; | |
116 | } |