diff options
Diffstat (limited to 'drivers/gpu/drm/drm_self_refresh_helper.c')
| -rw-r--r-- | drivers/gpu/drm/drm_self_refresh_helper.c | 281 |
1 files changed, 281 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_self_refresh_helper.c b/drivers/gpu/drm/drm_self_refresh_helper.c new file mode 100644 index 000000000..dd33fec5a --- /dev/null +++ b/drivers/gpu/drm/drm_self_refresh_helper.c @@ -0,0 +1,281 @@ +// SPDX-License-Identifier: MIT +/* + * Copyright (C) 2019 Google, Inc. + * + * Authors: + * Sean Paul <seanpaul@chromium.org> + */ +#include <linux/average.h> +#include <linux/bitops.h> +#include <linux/slab.h> +#include <linux/workqueue.h> + +#include <drm/drm_atomic.h> +#include <drm/drm_atomic_helper.h> +#include <drm/drm_connector.h> +#include <drm/drm_crtc.h> +#include <drm/drm_device.h> +#include <drm/drm_mode_config.h> +#include <drm/drm_modeset_lock.h> +#include <drm/drm_print.h> +#include <drm/drm_self_refresh_helper.h> + +/** + * DOC: overview + * + * This helper library provides an easy way for drivers to leverage the atomic + * framework to implement panel self refresh (SR) support. Drivers are + * responsible for initializing and cleaning up the SR helpers on load/unload + * (see &drm_self_refresh_helper_init/&drm_self_refresh_helper_cleanup). + * The connector is responsible for setting + * &drm_connector_state.self_refresh_aware to true at runtime if it is SR-aware + * (meaning it knows how to initiate self refresh on the panel). + * + * Once a crtc has enabled SR using &drm_self_refresh_helper_init, the + * helpers will monitor activity and call back into the driver to enable/disable + * SR as appropriate. The best way to think about this is that it's a DPMS + * on/off request with &drm_crtc_state.self_refresh_active set in crtc state + * that tells you to disable/enable SR on the panel instead of power-cycling it. + * + * During SR, drivers may choose to fully disable their crtc/encoder/bridge + * hardware (in which case no driver changes are necessary), or they can inspect + * &drm_crtc_state.self_refresh_active if they want to enter low power mode + * without full disable (in case full disable/enable is too slow). + * + * SR will be deactivated if there are any atomic updates affecting the + * pipe that is in SR mode. If a crtc is driving multiple connectors, all + * connectors must be SR aware and all will enter/exit SR mode at the same time. + * + * If the crtc and connector are SR aware, but the panel connected does not + * support it (or is otherwise unable to enter SR), the driver should fail + * atomic_check when &drm_crtc_state.self_refresh_active is true. + */ + +#define SELF_REFRESH_AVG_SEED_MS 200 + +DECLARE_EWMA(psr_time, 4, 4) + +struct drm_self_refresh_data { + struct drm_crtc *crtc; + struct delayed_work entry_work; + + struct mutex avg_mutex; + struct ewma_psr_time entry_avg_ms; + struct ewma_psr_time exit_avg_ms; +}; + +static void drm_self_refresh_helper_entry_work(struct work_struct *work) +{ + struct drm_self_refresh_data *sr_data = container_of( + to_delayed_work(work), + struct drm_self_refresh_data, entry_work); + struct drm_crtc *crtc = sr_data->crtc; + struct drm_device *dev = crtc->dev; + struct drm_modeset_acquire_ctx ctx; + struct drm_atomic_state *state; + struct drm_connector *conn; + struct drm_connector_state *conn_state; + struct drm_crtc_state *crtc_state; + int i, ret = 0; + + drm_modeset_acquire_init(&ctx, 0); + + state = drm_atomic_state_alloc(dev); + if (!state) { + ret = -ENOMEM; + goto out_drop_locks; + } + +retry: + state->acquire_ctx = &ctx; + + crtc_state = drm_atomic_get_crtc_state(state, crtc); + if (IS_ERR(crtc_state)) { + ret = PTR_ERR(crtc_state); + goto out; + } + + if (!crtc_state->enable) + goto out; + + ret = drm_atomic_add_affected_connectors(state, crtc); + if (ret) + goto out; + + for_each_new_connector_in_state(state, conn, conn_state, i) { + if (!conn_state->self_refresh_aware) + goto out; + } + + crtc_state->active = false; + crtc_state->self_refresh_active = true; + + ret = drm_atomic_commit(state); + if (ret) + goto out; + +out: + if (ret == -EDEADLK) { + drm_atomic_state_clear(state); + ret = drm_modeset_backoff(&ctx); + if (!ret) + goto retry; + } + + drm_atomic_state_put(state); + +out_drop_locks: + drm_modeset_drop_locks(&ctx); + drm_modeset_acquire_fini(&ctx); +} + +/** + * drm_self_refresh_helper_update_avg_times - Updates a crtc's SR time averages + * @state: the state which has just been applied to hardware + * @commit_time_ms: the amount of time in ms that this commit took to complete + * @new_self_refresh_mask: bitmask of crtc's that have self_refresh_active in + * new state + * + * Called after &drm_mode_config_funcs.atomic_commit_tail, this function will + * update the average entry/exit self refresh times on self refresh transitions. + * These averages will be used when calculating how long to delay before + * entering self refresh mode after activity. + */ +void +drm_self_refresh_helper_update_avg_times(struct drm_atomic_state *state, + unsigned int commit_time_ms, + unsigned int new_self_refresh_mask) +{ + struct drm_crtc *crtc; + struct drm_crtc_state *old_crtc_state; + int i; + + for_each_old_crtc_in_state(state, crtc, old_crtc_state, i) { + bool new_self_refresh_active = new_self_refresh_mask & BIT(i); + struct drm_self_refresh_data *sr_data = crtc->self_refresh_data; + struct ewma_psr_time *time; + + if (old_crtc_state->self_refresh_active == + new_self_refresh_active) + continue; + + if (new_self_refresh_active) + time = &sr_data->entry_avg_ms; + else + time = &sr_data->exit_avg_ms; + + mutex_lock(&sr_data->avg_mutex); + ewma_psr_time_add(time, commit_time_ms); + mutex_unlock(&sr_data->avg_mutex); + } +} +EXPORT_SYMBOL(drm_self_refresh_helper_update_avg_times); + +/** + * drm_self_refresh_helper_alter_state - Alters the atomic state for SR exit + * @state: the state currently being checked + * + * Called at the end of atomic check. This function checks the state for flags + * incompatible with self refresh exit and changes them. This is a bit + * disingenuous since userspace is expecting one thing and we're giving it + * another. However in order to keep self refresh entirely hidden from + * userspace, this is required. + * + * At the end, we queue up the self refresh entry work so we can enter PSR after + * the desired delay. + */ +void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state) +{ + struct drm_crtc *crtc; + struct drm_crtc_state *crtc_state; + int i; + + if (state->async_update || !state->allow_modeset) { + for_each_old_crtc_in_state(state, crtc, crtc_state, i) { + if (crtc_state->self_refresh_active) { + state->async_update = false; + state->allow_modeset = true; + break; + } + } + } + + for_each_new_crtc_in_state(state, crtc, crtc_state, i) { + struct drm_self_refresh_data *sr_data; + unsigned int delay; + + /* Don't trigger the entry timer when we're already in SR */ + if (crtc_state->self_refresh_active) + continue; + + sr_data = crtc->self_refresh_data; + if (!sr_data) + continue; + + mutex_lock(&sr_data->avg_mutex); + delay = (ewma_psr_time_read(&sr_data->entry_avg_ms) + + ewma_psr_time_read(&sr_data->exit_avg_ms)) * 2; + mutex_unlock(&sr_data->avg_mutex); + + mod_delayed_work(system_wq, &sr_data->entry_work, + msecs_to_jiffies(delay)); + } +} +EXPORT_SYMBOL(drm_self_refresh_helper_alter_state); + +/** + * drm_self_refresh_helper_init - Initializes self refresh helpers for a crtc + * @crtc: the crtc which supports self refresh supported displays + * + * Returns zero if successful or -errno on failure + */ +int drm_self_refresh_helper_init(struct drm_crtc *crtc) +{ + struct drm_self_refresh_data *sr_data = crtc->self_refresh_data; + + /* Helper is already initialized */ + if (WARN_ON(sr_data)) + return -EINVAL; + + sr_data = kzalloc(sizeof(*sr_data), GFP_KERNEL); + if (!sr_data) + return -ENOMEM; + + INIT_DELAYED_WORK(&sr_data->entry_work, + drm_self_refresh_helper_entry_work); + sr_data->crtc = crtc; + mutex_init(&sr_data->avg_mutex); + ewma_psr_time_init(&sr_data->entry_avg_ms); + ewma_psr_time_init(&sr_data->exit_avg_ms); + + /* + * Seed the averages so they're non-zero (and sufficiently large + * for even poorly performing panels). As time goes on, this will be + * averaged out and the values will trend to their true value. + */ + ewma_psr_time_add(&sr_data->entry_avg_ms, SELF_REFRESH_AVG_SEED_MS); + ewma_psr_time_add(&sr_data->exit_avg_ms, SELF_REFRESH_AVG_SEED_MS); + + crtc->self_refresh_data = sr_data; + return 0; +} +EXPORT_SYMBOL(drm_self_refresh_helper_init); + +/** + * drm_self_refresh_helper_cleanup - Cleans up self refresh helpers for a crtc + * @crtc: the crtc to cleanup + */ +void drm_self_refresh_helper_cleanup(struct drm_crtc *crtc) +{ + struct drm_self_refresh_data *sr_data = crtc->self_refresh_data; + + /* Helper is already uninitialized */ + if (!sr_data) + return; + + crtc->self_refresh_data = NULL; + + cancel_delayed_work_sync(&sr_data->entry_work); + kfree(sr_data); +} +EXPORT_SYMBOL(drm_self_refresh_helper_cleanup); |