drivers/gpu/drm/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/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
  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  *
 137  * Called after &drm_mode_config_funcs.atomic_commit_tail, this function will
 138  * update the average entry/exit self refresh times on self refresh transitions.
 139  * These averages will be used when calculating how long to delay before
 140  * entering self refresh mode after activity.
 141  */
 142 void drm_self_refresh_helper_update_avg_times(struct drm_atomic_state *state,
 143                                               unsigned int commit_time_ms)
 144 {
 145         struct drm_crtc *crtc;
 146         struct drm_crtc_state *old_crtc_state, *new_crtc_state;
 147         int i;
 148
 149         for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,
 150                                       new_crtc_state, i) {
 151                 struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
 152                 struct ewma_psr_time *time;
 153
 154                 if (old_crtc_state->self_refresh_active ==
 155                     new_crtc_state->self_refresh_active)
 156                         continue;
 157
 158                 if (new_crtc_state->self_refresh_active)
 159                         time = &sr_data->entry_avg_ms;
 160                 else
 161                         time = &sr_data->exit_avg_ms;
 162
 163                 mutex_lock(&sr_data->avg_mutex);
 164                 ewma_psr_time_add(time, commit_time_ms);
 165                 mutex_unlock(&sr_data->avg_mutex);
 166         }
 167 }
 168 EXPORT_SYMBOL(drm_self_refresh_helper_update_avg_times);
 169
 170 /**
 171  * drm_self_refresh_helper_alter_state - Alters the atomic state for SR exit
 172  * @state: the state currently being checked
 173  *
 174  * Called at the end of atomic check. This function checks the state for flags
 175  * incompatible with self refresh exit and changes them. This is a bit
 176  * disingenuous since userspace is expecting one thing and we're giving it
 177  * another. However in order to keep self refresh entirely hidden from
 178  * userspace, this is required.
 179  *
 180  * At the end, we queue up the self refresh entry work so we can enter PSR after
 181  * the desired delay.
 182  */
 183 void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state)
 184 {
 185         struct drm_crtc *crtc;
 186         struct drm_crtc_state *crtc_state;
 187         int i;
 188
 189         if (state->async_update || !state->allow_modeset) {
 190                 for_each_old_crtc_in_state(state, crtc, crtc_state, i) {
 191                         if (crtc_state->self_refresh_active) {
 192                                 state->async_update = false;
 193                                 state->allow_modeset = true;
 194                                 break;
 195                         }
 196                 }
 197         }
 198
 199         for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
 200                 struct drm_self_refresh_data *sr_data;
 201                 unsigned int delay;
 202
 203                 /* Don't trigger the entry timer when we're already in SR */
 204                 if (crtc_state->self_refresh_active)
 205                         continue;
 206
 207                 sr_data = crtc->self_refresh_data;
 208                 if (!sr_data)
 209                         continue;
 210
 211                 mutex_lock(&sr_data->avg_mutex);
 212                 delay = (ewma_psr_time_read(&sr_data->entry_avg_ms) +
 213                          ewma_psr_time_read(&sr_data->exit_avg_ms)) * 2;
 214                 mutex_unlock(&sr_data->avg_mutex);
 215
 216                 mod_delayed_work(system_wq, &sr_data->entry_work,
 217                                  msecs_to_jiffies(delay));
 218         }
 219 }
 220 EXPORT_SYMBOL(drm_self_refresh_helper_alter_state);
 221
 222 /**
 223  * drm_self_refresh_helper_init - Initializes self refresh helpers for a crtc
 224  * @crtc: the crtc which supports self refresh supported displays
 225  *
 226  * Returns zero if successful or -errno on failure
 227  */
 228 int drm_self_refresh_helper_init(struct drm_crtc *crtc)
 229 {
 230         struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
 231
 232         /* Helper is already initialized */
 233         if (WARN_ON(sr_data))
 234                 return -EINVAL;
 235
 236         sr_data = kzalloc(sizeof(*sr_data), GFP_KERNEL);
 237         if (!sr_data)
 238                 return -ENOMEM;
 239
 240         INIT_DELAYED_WORK(&sr_data->entry_work,
 241                           drm_self_refresh_helper_entry_work);
 242         sr_data->crtc = crtc;
 243         mutex_init(&sr_data->avg_mutex);
 244         ewma_psr_time_init(&sr_data->entry_avg_ms);
 245         ewma_psr_time_init(&sr_data->exit_avg_ms);
 246
 247         /*
 248          * Seed the averages so they're non-zero (and sufficiently large
 249          * for even poorly performing panels). As time goes on, this will be
 250          * averaged out and the values will trend to their true value.
 251          */
 252         ewma_psr_time_add(&sr_data->entry_avg_ms, SELF_REFRESH_AVG_SEED_MS);
 253         ewma_psr_time_add(&sr_data->exit_avg_ms, SELF_REFRESH_AVG_SEED_MS);
 254
 255         crtc->self_refresh_data = sr_data;
 256         return 0;
 257 }
 258 EXPORT_SYMBOL(drm_self_refresh_helper_init);
 259
 260 /**
 261  * drm_self_refresh_helper_cleanup - Cleans up self refresh helpers for a crtc
 262  * @crtc: the crtc to cleanup
 263  */
 264 void drm_self_refresh_helper_cleanup(struct drm_crtc *crtc)
 265 {
 266         struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
 267
 268         /* Helper is already uninitialized */
 269         if (!sr_data)
 270                 return;
 271
 272         crtc->self_refresh_data = NULL;
 273
 274         cancel_delayed_work_sync(&sr_data->entry_work);
 275         kfree(sr_data);
 276 }
 277 EXPORT_SYMBOL(drm_self_refresh_helper_cleanup);