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
 18struct 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
 26static 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
 55static 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
 70static 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 */
100int 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
116static 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 */
147int 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}