1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Thunderbolt driver - capabilities lookup
4 *
5 * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
6 * Copyright (C) 2018, Intel Corporation
7 */
8
9 #include <linux/slab.h>
10 #include <linux/errno.h>
11
12 #include "tb.h"
13
14 #define CAP_OFFSET_MAX 0xff
15 #define VSE_CAP_OFFSET_MAX 0xffff
16 #define TMU_ACCESS_EN BIT(20)
17
18 struct tb_cap_any {
19 union {
20 struct tb_cap_basic basic;
21 struct tb_cap_extended_short extended_short;
22 struct tb_cap_extended_long extended_long;
23 };
24 } __packed;
25
tb_port_enable_tmu(struct tb_port * port,bool enable)26 static int tb_port_enable_tmu(struct tb_port *port, bool enable)
27 {
28 struct tb_switch *sw = port->sw;
29 u32 value, offset;
30 int ret;
31
32 /*
33 * Legacy devices need to have TMU access enabled before port
34 * space can be fully accessed.
35 */
36 if (tb_switch_is_lr(sw))
37 offset = 0x26;
38 else if (tb_switch_is_er(sw))
39 offset = 0x2a;
40 else
41 return 0;
42
43 ret = tb_sw_read(sw, &value, TB_CFG_SWITCH, offset, 1);
44 if (ret)
45 return ret;
46
47 if (enable)
48 value |= TMU_ACCESS_EN;
49 else
50 value &= ~TMU_ACCESS_EN;
51
52 return tb_sw_write(sw, &value, TB_CFG_SWITCH, offset, 1);
53 }
54
tb_port_dummy_read(struct tb_port * port)55 static void tb_port_dummy_read(struct tb_port *port)
56 {
57 /*
58 * When reading from next capability pointer location in port
59 * config space the read data is not cleared on LR. To avoid
60 * reading stale data on next read perform one dummy read after
61 * port capabilities are walked.
62 */
63 if (tb_switch_is_lr(port->sw)) {
64 u32 dummy;
65
66 tb_port_read(port, &dummy, TB_CFG_PORT, 0, 1);
67 }
68 }
69
__tb_port_find_cap(struct tb_port * port,enum tb_port_cap cap)70 static int __tb_port_find_cap(struct tb_port *port, enum tb_port_cap cap)
71 {
72 u32 offset = 1;
73
74 do {
75 struct tb_cap_any header;
76 int ret;
77
78 ret = tb_port_read(port, &header, TB_CFG_PORT, offset, 1);
79 if (ret)
80 return ret;
81
82 if (header.basic.cap == cap)
83 return offset;
84
85 offset = header.basic.next;
86 } while (offset);
87
88 return -ENOENT;
89 }
90
91 /**
92 * tb_port_find_cap() - Find port capability
93 * @port: Port to find the capability for
94 * @cap: Capability to look
95 *
96 * Returns offset to start of capability or %-ENOENT if no such
97 * capability was found. Negative errno is returned if there was an
98 * error.
99 */
tb_port_find_cap(struct tb_port * port,enum tb_port_cap cap)100 int tb_port_find_cap(struct tb_port *port, enum tb_port_cap cap)
101 {
102 int ret;
103
104 ret = tb_port_enable_tmu(port, true);
105 if (ret)
106 return ret;
107
108 ret = __tb_port_find_cap(port, cap);
109
110 tb_port_dummy_read(port);
111 tb_port_enable_tmu(port, false);
112
113 return ret;
114 }
115
tb_switch_find_cap(struct tb_switch * sw,enum tb_switch_cap cap)116 static int tb_switch_find_cap(struct tb_switch *sw, enum tb_switch_cap cap)
117 {
118 int offset = sw->config.first_cap_offset;
119
120 while (offset > 0 && offset < CAP_OFFSET_MAX) {
121 struct tb_cap_any header;
122 int ret;
123
124 ret = tb_sw_read(sw, &header, TB_CFG_SWITCH, offset, 1);
125 if (ret)
126 return ret;
127
128 if (header.basic.cap == cap)
129 return offset;
130
131 offset = header.basic.next;
132 }
133
134 return -ENOENT;
135 }
136
137 /**
138 * tb_switch_find_vse_cap() - Find switch vendor specific capability
139 * @sw: Switch to find the capability for
140 * @vsec: Vendor specific capability to look
141 *
142 * Functions enumerates vendor specific capabilities (VSEC) of a switch
143 * and returns offset when capability matching @vsec is found. If no
144 * such capability is found returns %-ENOENT. In case of error returns
145 * negative errno.
146 */
tb_switch_find_vse_cap(struct tb_switch * sw,enum tb_switch_vse_cap vsec)147 int tb_switch_find_vse_cap(struct tb_switch *sw, enum tb_switch_vse_cap vsec)
148 {
149 struct tb_cap_any header;
150 int offset;
151
152 offset = tb_switch_find_cap(sw, TB_SWITCH_CAP_VSE);
153 if (offset < 0)
154 return offset;
155
156 while (offset > 0 && offset < VSE_CAP_OFFSET_MAX) {
157 int ret;
158
159 ret = tb_sw_read(sw, &header, TB_CFG_SWITCH, offset, 2);
160 if (ret)
161 return ret;
162
163 /*
164 * Extended vendor specific capabilities come in two
165 * flavors: short and long. The latter is used when
166 * offset is over 0xff.
167 */
168 if (offset >= CAP_OFFSET_MAX) {
169 if (header.extended_long.vsec_id == vsec)
170 return offset;
171 offset = header.extended_long.next;
172 } else {
173 if (header.extended_short.vsec_id == vsec)
174 return offset;
175 if (!header.extended_short.length)
176 return -ENOENT;
177 offset = header.extended_short.next;
178 }
179 }
180
181 return -ENOENT;
182 }
183