diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst index 5139705089f2..781129f78b06 100644 --- a/Documentation/gpu/drm-kms-helpers.rst +++ b/Documentation/gpu/drm-kms-helpers.rst @@ -92,6 +92,18 @@ GEM Atomic Helper Reference .. kernel-doc:: drivers/gpu/drm/drm_gem_atomic_helper.c :export: +VBLANK Helper Reference +----------------------- + +.. kernel-doc:: drivers/gpu/drm/drm_vblank_helper.c + :doc: overview + +.. kernel-doc:: include/drm/drm_vblank_helper.h + :internal: + +.. kernel-doc:: drivers/gpu/drm/drm_vblank_helper.c + :export: + Simple KMS Helper Reference =========================== diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile index 4dafbdc8f86a..5ba4ffdb8055 100644 --- a/drivers/gpu/drm/Makefile +++ b/drivers/gpu/drm/Makefile @@ -150,7 +150,8 @@ drm_kms_helper-y := \ drm_plane_helper.o \ drm_probe_helper.o \ drm_self_refresh_helper.o \ - drm_simple_kms_helper.o + drm_simple_kms_helper.o \ + drm_vblank_helper.o drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 46f59883183d..61e211fd3c9c 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -136,8 +136,17 @@ * vblanks after a timer has expired, which can be configured through the * ``vblankoffdelay`` module parameter. * - * Drivers for hardware without support for vertical-blanking interrupts - * must not call drm_vblank_init(). For such drivers, atomic helpers will + * Drivers for hardware without support for vertical-blanking interrupts can + * use DRM vblank timers to send vblank events at the rate of the current + * display mode's refresh. While not synchronized to the hardware's + * vertical-blanking regions, the timer helps DRM clients and compositors to + * adapt their update cycle to the display output. Drivers should set up + * vblanking as usual, but call drm_crtc_vblank_start_timer() and + * drm_crtc_vblank_cancel_timer() as part of their atomic mode setting. + * See also DRM vblank helpers for more information. + * + * Drivers without support for vertical-blanking interrupts nor timers must + * not call drm_vblank_init(). For these drivers, atomic helpers will * automatically generate fake vblank events as part of the display update. * This functionality also can be controlled by the driver by enabling and * disabling struct drm_crtc_state.no_vblank. @@ -508,6 +517,9 @@ static void drm_vblank_init_release(struct drm_device *dev, void *ptr) drm_WARN_ON(dev, READ_ONCE(vblank->enabled) && drm_core_check_feature(dev, DRIVER_MODESET)); + if (vblank->vblank_timer.crtc) + hrtimer_cancel(&vblank->vblank_timer.timer); + drm_vblank_destroy_worker(vblank); timer_delete_sync(&vblank->disable_timer); } @@ -2162,3 +2174,159 @@ err_free: return ret; } +/* + * VBLANK timer + */ + +static enum hrtimer_restart drm_vblank_timer_function(struct hrtimer *timer) +{ + struct drm_vblank_crtc_timer *vtimer = + container_of(timer, struct drm_vblank_crtc_timer, timer); + struct drm_crtc *crtc = vtimer->crtc; + const struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private; + struct drm_device *dev = crtc->dev; + unsigned long flags; + ktime_t interval; + u64 ret_overrun; + bool succ; + + spin_lock_irqsave(&vtimer->interval_lock, flags); + interval = vtimer->interval; + spin_unlock_irqrestore(&vtimer->interval_lock, flags); + + if (!interval) + return HRTIMER_NORESTART; + + ret_overrun = hrtimer_forward_now(&vtimer->timer, interval); + if (ret_overrun != 1) + drm_dbg_vbl(dev, "vblank timer overrun\n"); + + if (crtc_funcs->handle_vblank_timeout) + succ = crtc_funcs->handle_vblank_timeout(crtc); + else + succ = drm_crtc_handle_vblank(crtc); + if (!succ) + return HRTIMER_NORESTART; + + return HRTIMER_RESTART; +} + +/** + * drm_crtc_vblank_start_timer - Starts the vblank timer on the given CRTC + * @crtc: the CRTC + * + * Drivers should call this function from their CRTC's enable_vblank + * function to start a vblank timer. The timer will fire after the duration + * of a full frame. drm_crtc_vblank_cancel_timer() disables a running timer. + * + * Returns: + * 0 on success, or a negative errno code otherwise. + */ +int drm_crtc_vblank_start_timer(struct drm_crtc *crtc) +{ + struct drm_vblank_crtc *vblank = drm_crtc_vblank_crtc(crtc); + struct drm_vblank_crtc_timer *vtimer = &vblank->vblank_timer; + unsigned long flags; + + if (!vtimer->crtc) { + /* + * Set up the data structures on the first invocation. + */ + vtimer->crtc = crtc; + spin_lock_init(&vtimer->interval_lock); + hrtimer_setup(&vtimer->timer, drm_vblank_timer_function, + CLOCK_MONOTONIC, HRTIMER_MODE_REL); + } else { + /* + * Timer should not be active. If it is, wait for the + * previous cancel operations to finish. + */ + while (hrtimer_active(&vtimer->timer)) + hrtimer_try_to_cancel(&vtimer->timer); + } + + drm_calc_timestamping_constants(crtc, &crtc->mode); + + spin_lock_irqsave(&vtimer->interval_lock, flags); + vtimer->interval = ns_to_ktime(vblank->framedur_ns); + spin_unlock_irqrestore(&vtimer->interval_lock, flags); + + hrtimer_start(&vtimer->timer, vtimer->interval, HRTIMER_MODE_REL); + + return 0; +} +EXPORT_SYMBOL(drm_crtc_vblank_start_timer); + +/** + * drm_crtc_vblank_start_timer - Cancels the given CRTC's vblank timer + * @crtc: the CRTC + * + * Drivers should call this function from their CRTC's disable_vblank + * function to stop a vblank timer. + */ +void drm_crtc_vblank_cancel_timer(struct drm_crtc *crtc) +{ + struct drm_vblank_crtc *vblank = drm_crtc_vblank_crtc(crtc); + struct drm_vblank_crtc_timer *vtimer = &vblank->vblank_timer; + unsigned long flags; + + /* + * Calling hrtimer_cancel() can result in a deadlock with DRM's + * vblank_time_lime_lock and hrtimers' softirq_expiry_lock. So + * clear interval and indicate cancellation. The timer function + * will cancel itself on the next invocation. + */ + + spin_lock_irqsave(&vtimer->interval_lock, flags); + vtimer->interval = 0; + spin_unlock_irqrestore(&vtimer->interval_lock, flags); + + hrtimer_try_to_cancel(&vtimer->timer); +} +EXPORT_SYMBOL(drm_crtc_vblank_cancel_timer); + +/** + * drm_crtc_vblank_get_vblank_timeout - Returns the vblank timeout + * @crtc: The CRTC + * @vblank_time: Returns the next vblank timestamp + * + * The helper drm_crtc_vblank_get_vblank_timeout() returns the next vblank + * timestamp of the CRTC's vblank timer according to the timer's expiry + * time. + */ +void drm_crtc_vblank_get_vblank_timeout(struct drm_crtc *crtc, ktime_t *vblank_time) +{ + struct drm_vblank_crtc *vblank = drm_crtc_vblank_crtc(crtc); + struct drm_vblank_crtc_timer *vtimer = &vblank->vblank_timer; + u64 cur_count; + ktime_t cur_time; + + if (!READ_ONCE(vblank->enabled)) { + *vblank_time = ktime_get(); + return; + } + + /* + * A concurrent vblank timeout could update the expires field before + * we compare it with the vblank time. Hence we'd compare the old + * expiry time to the new vblank time; deducing the timer had already + * expired. Reread until we get consistent values from both fields. + */ + do { + cur_count = drm_crtc_vblank_count_and_time(crtc, &cur_time); + *vblank_time = READ_ONCE(vtimer->timer.node.expires); + } while (cur_count != drm_crtc_vblank_count_and_time(crtc, &cur_time)); + + if (drm_WARN_ON(crtc->dev, !ktime_compare(*vblank_time, cur_time))) + return; /* Already expired */ + + /* + * To prevent races we roll the hrtimer forward before we do any + * interrupt processing - this is how real hw works (the interrupt + * is only generated after all the vblank registers are updated) + * and what the vblank core expects. Therefore we need to always + * correct the timestamp by one frame. + */ + *vblank_time = ktime_sub(*vblank_time, vtimer->interval); +} +EXPORT_SYMBOL(drm_crtc_vblank_get_vblank_timeout); diff --git a/drivers/gpu/drm/drm_vblank_helper.c b/drivers/gpu/drm/drm_vblank_helper.c new file mode 100644 index 000000000000..f94d1e706191 --- /dev/null +++ b/drivers/gpu/drm/drm_vblank_helper.c @@ -0,0 +1,96 @@ +// SPDX-License-Identifier: MIT + +#include +#include +#include +#include +#include +#include + +/** + * DOC: overview + * + * The vblank helper library provides functions for supporting vertical + * blanking in DRM drivers. + * + * For vblank timers, several callback implementations are available. + * Drivers enable support for vblank timers by setting the vblank callbacks + * in struct &drm_crtc_funcs to the helpers provided by this library. The + * initializer macro DRM_CRTC_VBLANK_TIMER_FUNCS does this conveniently. + * + * Once the driver enables vblank support with drm_vblank_init(), each + * CRTC's vblank timer fires according to the programmed display mode. By + * default, the vblank timer invokes drm_crtc_handle_vblank(). Drivers with + * more specific requirements can set their own handler function in + * struct &drm_crtc_helper_funcs.handle_vblank_timeout. + */ + +/* + * VBLANK timer + */ + +/** + * drm_crtc_vblank_helper_enable_vblank_timer - Implements struct &drm_crtc_funcs.enable_vblank + * @crtc: The CRTC + * + * The helper drm_crtc_vblank_helper_enable_vblank_timer() implements + * enable_vblank of struct drm_crtc_helper_funcs for CRTCs that require + * a VBLANK timer. It sets up the timer on the first invocation. The + * started timer expires after the current frame duration. See struct + * &drm_vblank_crtc.framedur_ns. + * + * See also struct &drm_crtc_helper_funcs.enable_vblank. + * + * Returns: + * 0 on success, or a negative errno code otherwise. + */ +int drm_crtc_vblank_helper_enable_vblank_timer(struct drm_crtc *crtc) +{ + return drm_crtc_vblank_start_timer(crtc); +} +EXPORT_SYMBOL(drm_crtc_vblank_helper_enable_vblank_timer); + +/** + * drm_crtc_vblank_helper_disable_vblank_timer - Implements struct &drm_crtc_funcs.disable_vblank + * @crtc: The CRTC + * + * The helper drm_crtc_vblank_helper_disable_vblank_timer() implements + * disable_vblank of struct drm_crtc_funcs for CRTCs that require a + * VBLANK timer. + * + * See also struct &drm_crtc_helper_funcs.disable_vblank. + */ +void drm_crtc_vblank_helper_disable_vblank_timer(struct drm_crtc *crtc) +{ + drm_crtc_vblank_cancel_timer(crtc); +} +EXPORT_SYMBOL(drm_crtc_vblank_helper_disable_vblank_timer); + +/** + * drm_crtc_vblank_helper_get_vblank_timestamp_from_timer - + * Implements struct &drm_crtc_funcs.get_vblank_timestamp + * @crtc: The CRTC + * @max_error: Maximum acceptable error + * @vblank_time: Returns the next vblank timestamp + * @in_vblank_irq: True is called from drm_crtc_handle_vblank() + * + * The helper drm_crtc_helper_get_vblank_timestamp_from_timer() implements + * get_vblank_timestamp of struct drm_crtc_funcs for CRTCs that require a + * VBLANK timer. It returns the timestamp according to the timer's expiry + * time. + * + * See also struct &drm_crtc_funcs.get_vblank_timestamp. + * + * Returns: + * True on success, or false otherwise. + */ +bool drm_crtc_vblank_helper_get_vblank_timestamp_from_timer(struct drm_crtc *crtc, + int *max_error, + ktime_t *vblank_time, + bool in_vblank_irq) +{ + drm_crtc_vblank_get_vblank_timeout(crtc, vblank_time); + + return true; +} +EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp_from_timer); diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h index ce7c7aeac887..fe32854b7ffe 100644 --- a/include/drm/drm_modeset_helper_vtables.h +++ b/include/drm/drm_modeset_helper_vtables.h @@ -490,6 +490,18 @@ struct drm_crtc_helper_funcs { bool in_vblank_irq, int *vpos, int *hpos, ktime_t *stime, ktime_t *etime, const struct drm_display_mode *mode); + + /** + * @handle_vblank_timeout: Handles timeouts of the vblank timer. + * + * Called by CRTC's the vblank timer on each timeout. Semantics is + * equivalient to drm_crtc_handle_vblank(). Implementations should + * invoke drm_crtc_handle_vblank() as part of processing the timeout. + * + * This callback is optional. If unset, the vblank timer invokes + * drm_crtc_handle_vblank() directly. + */ + bool (*handle_vblank_timeout)(struct drm_crtc *crtc); }; /** diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h index 151ab1e85b1b..ffa564d79638 100644 --- a/include/drm/drm_vblank.h +++ b/include/drm/drm_vblank.h @@ -25,6 +25,7 @@ #define _DRM_VBLANK_H_ #include +#include #include #include #include @@ -103,6 +104,28 @@ struct drm_vblank_crtc_config { bool disable_immediate; }; +/** + * struct drm_vblank_crtc_timer - vblank timer for a CRTC + */ +struct drm_vblank_crtc_timer { + /** + * @timer: The vblank's high-resolution timer + */ + struct hrtimer timer; + /** + * @interval_lock: Protects @interval + */ + spinlock_t interval_lock; + /** + * @interval: Duration between two vblanks + */ + ktime_t interval; + /** + * @crtc: The timer's CRTC + */ + struct drm_crtc *crtc; +}; + /** * struct drm_vblank_crtc - vblank tracking for a CRTC * @@ -254,6 +277,11 @@ struct drm_vblank_crtc { * cancelled. */ wait_queue_head_t work_wait_queue; + + /** + * @vblank_timer: Holds the state of the vblank timer + */ + struct drm_vblank_crtc_timer vblank_timer; }; struct drm_vblank_crtc *drm_crtc_vblank_crtc(struct drm_crtc *crtc); @@ -290,6 +318,10 @@ wait_queue_head_t *drm_crtc_vblank_waitqueue(struct drm_crtc *crtc); void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc, u32 max_vblank_count); +int drm_crtc_vblank_start_timer(struct drm_crtc *crtc); +void drm_crtc_vblank_cancel_timer(struct drm_crtc *crtc); +void drm_crtc_vblank_get_vblank_timeout(struct drm_crtc *crtc, ktime_t *vblank_time); + /* * Helpers for struct drm_crtc_funcs */ diff --git a/include/drm/drm_vblank_helper.h b/include/drm/drm_vblank_helper.h new file mode 100644 index 000000000000..74a971d0cfba --- /dev/null +++ b/include/drm/drm_vblank_helper.h @@ -0,0 +1,33 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ + +#ifndef _DRM_VBLANK_HELPER_H_ +#define _DRM_VBLANK_HELPER_H_ + +#include +#include + +struct drm_crtc; + +/* + * VBLANK timer + */ + +int drm_crtc_vblank_helper_enable_vblank_timer(struct drm_crtc *crtc); +void drm_crtc_vblank_helper_disable_vblank_timer(struct drm_crtc *crtc); +bool drm_crtc_vblank_helper_get_vblank_timestamp_from_timer(struct drm_crtc *crtc, + int *max_error, + ktime_t *vblank_time, + bool in_vblank_irq); + +/** + * DRM_CRTC_VBLANK_TIMER_FUNCS - Default implementation for VBLANK timers + * + * This macro initializes struct &drm_crtc_funcs to default helpers for + * VBLANK timers. + */ +#define DRM_CRTC_VBLANK_TIMER_FUNCS \ + .enable_vblank = drm_crtc_vblank_helper_enable_vblank_timer, \ + .disable_vblank = drm_crtc_vblank_helper_disable_vblank_timer, \ + .get_vblank_timestamp = drm_crtc_vblank_helper_get_vblank_timestamp_from_timer + +#endif