1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
|
/*
* nextpnr -- Next Generation Place and Route
*
* Copyright (C) 2018 David Shah <david@symbioticeda.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
#include "timing.h"
#include <algorithm>
#include <unordered_map>
#include <utility>
#include "log.h"
#include "util.h"
NEXTPNR_NAMESPACE_BEGIN
static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t slack);
// Follow a path, returning budget to annotate
static delay_t follow_user_port(Context *ctx, PortRef &user, int path_length, delay_t slack)
{
delay_t value;
if (ctx->getPortClock(user.cell, user.port) != IdString()) {
// At the end of a timing path (arguably, should check setup time
// here too)
value = slack / path_length;
} else {
// Default to the path ending here, if no further paths found
value = slack / path_length;
// Follow outputs of the user
for (auto port : user.cell->ports) {
if (port.second.type == PORT_OUT) {
delay_t comb_delay;
// Look up delay through this path
bool is_path = ctx->getCellDelay(user.cell, user.port, port.first, comb_delay);
if (is_path) {
NetInfo *net = port.second.net;
if (net) {
delay_t path_budget = follow_net(ctx, net, path_length, slack - comb_delay);
value = std::min(value, path_budget);
}
}
}
}
}
if (value < user.budget) {
user.budget = value;
}
return value;
}
static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t slack)
{
delay_t net_budget = slack / (path_length + 1);
for (auto &usr : net->users) {
net_budget = std::min(net_budget, follow_user_port(ctx, usr, path_length + 1, slack));
}
return net_budget;
}
void assign_budget(Context *ctx)
{
log_break();
log_info("Annotating ports with timing budgets\n");
// Clear delays to a very high value first
delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
for (auto &net : ctx->nets) {
for (auto &usr : net.second->users) {
usr.budget = default_slack;
}
}
// Go through all clocked drivers and set up paths
for (auto &cell : ctx->cells) {
for (auto port : cell.second->ports) {
if (port.second.type == PORT_OUT) {
IdString clock_domain = ctx->getPortClock(cell.second.get(), port.first);
if (clock_domain != IdString()) {
delay_t slack = delay_t(1.0e12 / ctx->target_freq); // TODO: clock constraints
if (port.second.net)
follow_net(ctx, port.second.net, 0, slack);
}
}
}
}
// Post-allocation check
for (auto &net : ctx->nets) {
for (auto user : net.second->users) {
if (user.budget < 0)
log_warning("port %s.%s, connected to net '%s', has negative "
"timing budget of %fns\n",
user.cell->name.c_str(ctx), user.port.c_str(ctx), net.first.c_str(ctx),
ctx->getDelayNS(user.budget));
if (ctx->verbose)
log_info("port %s.%s, connected to net '%s', has "
"timing budget of %fns\n",
user.cell->name.c_str(ctx), user.port.c_str(ctx), net.first.c_str(ctx),
ctx->getDelayNS(user.budget));
}
}
log_info("Checksum: 0x%08x\n", ctx->checksum());
}
typedef std::unordered_map<const PortInfo*, delay_t> updates_t;
typedef std::unordered_map<const PortInfo*, delay_t> delays_t;
static delay_t follow_net_update(Context *ctx, NetInfo *net, int path_length, delay_t slack, const delays_t& delays, updates_t& updates);
// Follow a path, returning budget to annotate
static delay_t follow_user_port_update(Context *ctx, PortRef &user, int path_length, delay_t slack, const delays_t& delays, updates_t& updates)
{
delay_t value;
if (ctx->getPortClock(user.cell, user.port) != IdString()) {
// At the end of a timing path (arguably, should check setup time
// here too)
value = slack / path_length;
} else {
// Default to the path ending here, if no further paths found
value = slack / path_length;
// Follow outputs of the user
for (auto& port : user.cell->ports) {
if (port.second.type == PORT_OUT) {
delay_t comb_delay;
// Look up delay through this path
bool is_path = ctx->getCellDelay(user.cell, user.port, port.first, comb_delay);
if (is_path) {
NetInfo *net = port.second.net;
if (net) {
delay_t path_budget = follow_net_update(ctx, net, path_length, slack - comb_delay, delays, updates);
value = std::min(value, path_budget);
}
}
}
}
}
auto ret = updates.emplace(&user.cell->ports.at(user.port), value);
if (!ret.second && value < ret.first->second) {
ret.first->second = value;
}
return value;
}
static delay_t follow_net_update(Context *ctx, NetInfo *net, int path_length, delay_t slack, const delays_t& delays,updates_t& updates)
{
delay_t net_budget = slack / (path_length + 1);
for (auto& usr : net->users) {
net_budget = std::min(net_budget, follow_user_port_update(ctx, usr, path_length + 1, slack - get_or_default(delays, &usr.cell->ports.at(usr.port), 0.), delays, updates));
}
return net_budget;
}
void update_budget(Context *ctx)
{
delays_t delays;
updates_t updates;
// Compute the delay for every pin on every net
for (auto &n : ctx->nets) {
auto net = n.second.get();
int driver_x, driver_y;
bool driver_gb;
CellInfo *driver_cell = net->driver.cell;
if (!driver_cell)
continue;
if (driver_cell->bel == BelId())
continue;
ctx->estimatePosition(driver_cell->bel, driver_x, driver_y, driver_gb);
WireId drv_wire = ctx->getWireBelPin(driver_cell->bel, ctx->portPinFromId(net->driver.port));
if (driver_gb)
continue;
for (auto& load : net->users) {
if (load.cell == nullptr)
continue;
CellInfo *load_cell = load.cell;
if (load_cell->bel == BelId())
continue;
WireId user_wire = ctx->getWireBelPin(load_cell->bel, ctx->portPinFromId(load.port));
delay_t raw_wl = ctx->estimateDelay(drv_wire, user_wire);
delays.emplace(&load_cell->ports.at(load.port), raw_wl);
}
}
// Go through all clocked drivers and distribute the available path slack evenly into every budget
for (auto &cell : ctx->cells) {
for (auto& port : cell.second->ports) {
if (port.second.type == PORT_OUT) {
IdString clock_domain = ctx->getPortClock(cell.second.get(), port.first);
if (clock_domain != IdString()) {
if (port.second.net)
follow_net_update(ctx, port.second.net, 0, delay_t(1.0e12 / ctx->target_freq) - get_or_default(delays, &port.second, 0.), delays, updates);
}
}
}
}
// Update the budgets
for (auto &net : ctx->nets) {
for (auto& user : net.second->users) {
auto pi = &user.cell->ports.at(user.port);
auto it = updates.find(pi);
if (it == updates.end()) continue;
user.budget = delays.at(pi) + it->second;
// Post-update check
// if (user.budget < 0)
// log_warning("port %s.%s, connected to net '%s', has negative "
// "timing budget of %fns\n",
// user.cell->name.c_str(ctx), user.port.c_str(ctx), net.first.c_str(ctx),
// ctx->getDelayNS(user.budget));
// if (ctx->verbose)
// log_info("port %s.%s, connected to net '%s', has "
// "timing budget of %fns\n",
// user.cell->name.c_str(ctx), user.port.c_str(ctx), net.first.c_str(ctx),
// ctx->getDelayNS(user.budget));
}
}
}
NEXTPNR_NAMESPACE_END
|
