1 // SPDX-License-Identifier: MIT
2 /*
3 * Copyright (C) 2019 Google, Inc.
4 *
5 * Authors:
6 * Sean Paul <seanpaul@chromium.org>
7 */
8 #include <linux/average.h>
9 #include <linux/bitops.h>
10 #include <linux/slab.h>
11 #include <linux/workqueue.h>
12
13 #include <drm/drm_atomic.h>
14 #include <drm/drm_atomic_helper.h>
15 #include <drm/drm_connector.h>
16 #include <drm/drm_crtc.h>
17 #include <drm/drm_device.h>
18 #include <drm/drm_mode_config.h>
19 #include <drm/drm_modeset_lock.h>
20 #include <drm/drm_print.h>
21 #include <drm/drm_self_refresh_helper.h>
22
23 /**
24 * DOC: overview
25 *
26 * This helper library provides an easy way for drivers to leverage the atomic
27 * framework to implement panel self refresh (SR) support. Drivers are
28 * responsible for initializing and cleaning up the SR helpers on load/unload
29 * (see &drm_self_refresh_helper_init/&drm_self_refresh_helper_cleanup).
30 * The connector is responsible for setting
31 * &drm_connector_state.self_refresh_aware to true at runtime if it is SR-aware
32 * (meaning it knows how to initiate self refresh on the panel).
33 *
34 * Once a crtc has enabled SR using &drm_self_refresh_helper_init, the
35 * helpers will monitor activity and call back into the driver to enable/disable
36 * SR as appropriate. The best way to think about this is that it's a DPMS
37 * on/off request with &drm_crtc_state.self_refresh_active set in crtc state
38 * that tells you to disable/enable SR on the panel instead of power-cycling it.
39 *
40 * During SR, drivers may choose to fully disable their crtc/encoder/bridge
41 * hardware (in which case no driver changes are necessary), or they can inspect
42 * &drm_crtc_state.self_refresh_active if they want to enter low power mode
43 * without full disable (in case full disable/enable is too slow).
44 *
45 * SR will be deactivated if there are any atomic updates affecting the
46 * pipe that is in SR mode. If a crtc is driving multiple connectors, all
47 * connectors must be SR aware and all will enter/exit SR mode at the same time.
48 *
49 * If the crtc and connector are SR aware, but the panel connected does not
50 * support it (or is otherwise unable to enter SR), the driver should fail
51 * atomic_check when &drm_crtc_state.self_refresh_active is true.
52 */
53
54 #define SELF_REFRESH_AVG_SEED_MS 200
55
56 DECLARE_EWMA(psr_time, 4, 4)
57
58 struct drm_self_refresh_data {
59 struct drm_crtc *crtc;
60 struct delayed_work entry_work;
61
62 struct mutex avg_mutex;
63 struct ewma_psr_time entry_avg_ms;
64 struct ewma_psr_time exit_avg_ms;
65 };
66
drm_self_refresh_helper_entry_work(struct work_struct * work)67 static void drm_self_refresh_helper_entry_work(struct work_struct *work)
68 {
69 struct drm_self_refresh_data *sr_data = container_of(
70 to_delayed_work(work),
71 struct drm_self_refresh_data, entry_work);
72 struct drm_crtc *crtc = sr_data->crtc;
73 struct drm_device *dev = crtc->dev;
74 struct drm_modeset_acquire_ctx ctx;
75 struct drm_atomic_state *state;
76 struct drm_connector *conn;
77 struct drm_connector_state *conn_state;
78 struct drm_crtc_state *crtc_state;
79 int i, ret = 0;
80
81 drm_modeset_acquire_init(&ctx, 0);
82
83 state = drm_atomic_state_alloc(dev);
84 if (!state) {
85 ret = -ENOMEM;
86 goto out_drop_locks;
87 }
88
89 retry:
90 state->acquire_ctx = &ctx;
91
92 crtc_state = drm_atomic_get_crtc_state(state, crtc);
93 if (IS_ERR(crtc_state)) {
94 ret = PTR_ERR(crtc_state);
95 goto out;
96 }
97
98 if (!crtc_state->enable)
99 goto out;
100
101 ret = drm_atomic_add_affected_connectors(state, crtc);
102 if (ret)
103 goto out;
104
105 for_each_new_connector_in_state(state, conn, conn_state, i) {
106 if (!conn_state->self_refresh_aware)
107 goto out;
108 }
109
110 crtc_state->active = false;
111 crtc_state->self_refresh_active = true;
112
113 ret = drm_atomic_commit(state);
114 if (ret)
115 goto out;
116
117 out:
118 if (ret == -EDEADLK) {
119 drm_atomic_state_clear(state);
120 ret = drm_modeset_backoff(&ctx);
121 if (!ret)
122 goto retry;
123 }
124
125 drm_atomic_state_put(state);
126
127 out_drop_locks:
128 drm_modeset_drop_locks(&ctx);
129 drm_modeset_acquire_fini(&ctx);
130 }
131
132 /**
133 * drm_self_refresh_helper_update_avg_times - Updates a crtc's SR time averages
134 * @state: the state which has just been applied to hardware
135 * @commit_time_ms: the amount of time in ms that this commit took to complete
136 * @new_self_refresh_mask: bitmask of crtc's that have self_refresh_active in
137 * new state
138 *
139 * Called after &drm_mode_config_funcs.atomic_commit_tail, this function will
140 * update the average entry/exit self refresh times on self refresh transitions.
141 * These averages will be used when calculating how long to delay before
142 * entering self refresh mode after activity.
143 */
144 void
drm_self_refresh_helper_update_avg_times(struct drm_atomic_state * state,unsigned int commit_time_ms,unsigned int new_self_refresh_mask)145 drm_self_refresh_helper_update_avg_times(struct drm_atomic_state *state,
146 unsigned int commit_time_ms,
147 unsigned int new_self_refresh_mask)
148 {
149 struct drm_crtc *crtc;
150 struct drm_crtc_state *old_crtc_state;
151 int i;
152
153 for_each_old_crtc_in_state(state, crtc, old_crtc_state, i) {
154 bool new_self_refresh_active = new_self_refresh_mask & BIT(i);
155 struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
156 struct ewma_psr_time *time;
157
158 if (old_crtc_state->self_refresh_active ==
159 new_self_refresh_active)
160 continue;
161
162 if (new_self_refresh_active)
163 time = &sr_data->entry_avg_ms;
164 else
165 time = &sr_data->exit_avg_ms;
166
167 mutex_lock(&sr_data->avg_mutex);
168 ewma_psr_time_add(time, commit_time_ms);
169 mutex_unlock(&sr_data->avg_mutex);
170 }
171 }
172 EXPORT_SYMBOL(drm_self_refresh_helper_update_avg_times);
173
174 /**
175 * drm_self_refresh_helper_alter_state - Alters the atomic state for SR exit
176 * @state: the state currently being checked
177 *
178 * Called at the end of atomic check. This function checks the state for flags
179 * incompatible with self refresh exit and changes them. This is a bit
180 * disingenuous since userspace is expecting one thing and we're giving it
181 * another. However in order to keep self refresh entirely hidden from
182 * userspace, this is required.
183 *
184 * At the end, we queue up the self refresh entry work so we can enter PSR after
185 * the desired delay.
186 */
drm_self_refresh_helper_alter_state(struct drm_atomic_state * state)187 void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state)
188 {
189 struct drm_crtc *crtc;
190 struct drm_crtc_state *crtc_state;
191 int i;
192
193 if (state->async_update || !state->allow_modeset) {
194 for_each_old_crtc_in_state(state, crtc, crtc_state, i) {
195 if (crtc_state->self_refresh_active) {
196 state->async_update = false;
197 state->allow_modeset = true;
198 break;
199 }
200 }
201 }
202
203 for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
204 struct drm_self_refresh_data *sr_data;
205 unsigned int delay;
206
207 /* Don't trigger the entry timer when we're already in SR */
208 if (crtc_state->self_refresh_active)
209 continue;
210
211 sr_data = crtc->self_refresh_data;
212 if (!sr_data)
213 continue;
214
215 mutex_lock(&sr_data->avg_mutex);
216 delay = (ewma_psr_time_read(&sr_data->entry_avg_ms) +
217 ewma_psr_time_read(&sr_data->exit_avg_ms)) * 2;
218 mutex_unlock(&sr_data->avg_mutex);
219
220 mod_delayed_work(system_wq, &sr_data->entry_work,
221 msecs_to_jiffies(delay));
222 }
223 }
224 EXPORT_SYMBOL(drm_self_refresh_helper_alter_state);
225
226 /**
227 * drm_self_refresh_helper_init - Initializes self refresh helpers for a crtc
228 * @crtc: the crtc which supports self refresh supported displays
229 *
230 * Returns zero if successful or -errno on failure
231 */
drm_self_refresh_helper_init(struct drm_crtc * crtc)232 int drm_self_refresh_helper_init(struct drm_crtc *crtc)
233 {
234 struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
235
236 /* Helper is already initialized */
237 if (WARN_ON(sr_data))
238 return -EINVAL;
239
240 sr_data = kzalloc(sizeof(*sr_data), GFP_KERNEL);
241 if (!sr_data)
242 return -ENOMEM;
243
244 INIT_DELAYED_WORK(&sr_data->entry_work,
245 drm_self_refresh_helper_entry_work);
246 sr_data->crtc = crtc;
247 mutex_init(&sr_data->avg_mutex);
248 ewma_psr_time_init(&sr_data->entry_avg_ms);
249 ewma_psr_time_init(&sr_data->exit_avg_ms);
250
251 /*
252 * Seed the averages so they're non-zero (and sufficiently large
253 * for even poorly performing panels). As time goes on, this will be
254 * averaged out and the values will trend to their true value.
255 */
256 ewma_psr_time_add(&sr_data->entry_avg_ms, SELF_REFRESH_AVG_SEED_MS);
257 ewma_psr_time_add(&sr_data->exit_avg_ms, SELF_REFRESH_AVG_SEED_MS);
258
259 crtc->self_refresh_data = sr_data;
260 return 0;
261 }
262 EXPORT_SYMBOL(drm_self_refresh_helper_init);
263
264 /**
265 * drm_self_refresh_helper_cleanup - Cleans up self refresh helpers for a crtc
266 * @crtc: the crtc to cleanup
267 */
drm_self_refresh_helper_cleanup(struct drm_crtc * crtc)268 void drm_self_refresh_helper_cleanup(struct drm_crtc *crtc)
269 {
270 struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
271
272 /* Helper is already uninitialized */
273 if (!sr_data)
274 return;
275
276 crtc->self_refresh_data = NULL;
277
278 cancel_delayed_work_sync(&sr_data->entry_work);
279 kfree(sr_data);
280 }
281 EXPORT_SYMBOL(drm_self_refresh_helper_cleanup);
282