/*
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* Thunderbolt Cactus Ridge driver - capabilities lookup
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*
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* Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
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*/
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#include <linux/slab.h>
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#include <linux/errno.h>
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#include "tb.h"
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struct tb_cap_any {
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union {
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struct tb_cap_basic basic;
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struct tb_cap_extended_short extended_short;
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struct tb_cap_extended_long extended_long;
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};
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} __packed;
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static bool tb_cap_is_basic(struct tb_cap_any *cap)
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{
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/* basic.cap is u8. This checks only the lower 8 bit of cap. */
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return cap->basic.cap != 5;
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}
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static bool tb_cap_is_long(struct tb_cap_any *cap)
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{
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return !tb_cap_is_basic(cap)
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&& cap->extended_short.next == 0
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&& cap->extended_short.length == 0;
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}
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static enum tb_cap tb_cap(struct tb_cap_any *cap)
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{
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if (tb_cap_is_basic(cap))
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return cap->basic.cap;
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else
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/* extended_short/long have cap at the same offset. */
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return cap->extended_short.cap;
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}
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static u32 tb_cap_next(struct tb_cap_any *cap, u32 offset)
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{
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int next;
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if (offset == 1) {
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/*
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* The first pointer is part of the switch header and always
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* a simple pointer.
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*/
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next = cap->basic.next;
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} else {
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/*
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* Somehow Intel decided to use 3 different types of capability
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* headers. It is not like anyone could have predicted that
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* single byte offsets are not enough...
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*/
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if (tb_cap_is_basic(cap))
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next = cap->basic.next;
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else if (!tb_cap_is_long(cap))
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next = cap->extended_short.next;
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else
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next = cap->extended_long.next;
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}
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/*
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* "Hey, we could terminate some capability lists with a null offset
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* and others with a pointer to the last element." - "Great idea!"
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*/
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if (next == offset)
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return 0;
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return next;
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}
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/**
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* tb_find_cap() - find a capability
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*
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* Return: Returns a positive offset if the capability was found and 0 if not.
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* Returns an error code on failure.
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*/
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int tb_find_cap(struct tb_port *port, enum tb_cfg_space space, enum tb_cap cap)
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{
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u32 offset = 1;
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struct tb_cap_any header;
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int res;
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int retries = 10;
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while (retries--) {
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res = tb_port_read(port, &header, space, offset, 1);
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if (res) {
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/* Intel needs some help with linked lists. */
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if (space == TB_CFG_PORT && offset == 0xa
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&& port->config.type == TB_TYPE_DP_HDMI_OUT) {
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offset = 0x39;
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continue;
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}
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return res;
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}
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if (offset != 1) {
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if (tb_cap(&header) == cap)
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return offset;
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if (tb_cap_is_long(&header)) {
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/* tb_cap_extended_long is 2 dwords */
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res = tb_port_read(port, &header, space,
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offset, 2);
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if (res)
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return res;
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}
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}
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offset = tb_cap_next(&header, offset);
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if (!offset)
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return 0;
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}
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tb_port_WARN(port,
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"run out of retries while looking for cap %#x in config space %d, last offset: %#x\n",
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cap, space, offset);
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return -EIO;
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}
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