| Andreas Noever | e2b8785 | 2014-06-03 22:04:03 +0200 | [diff] [blame] | 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 | } |