drm_self_refresh_helper.c

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