diff options
Diffstat (limited to 'drivers/gpu/drm/drm_vblank.c')
| -rw-r--r-- | drivers/gpu/drm/drm_vblank.c | 98 |
1 files changed, 77 insertions, 21 deletions
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index da7b0b0c1090..2d5ce690d214 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -30,6 +30,7 @@ #include <drm/drm_crtc.h> #include <drm/drm_drv.h> #include <drm/drm_framebuffer.h> +#include <drm/drm_managed.h> #include <drm/drm_modeset_helper_vtables.h> #include <drm/drm_print.h> #include <drm/drm_vblank.h> @@ -40,6 +41,69 @@ /** * DOC: vblank handling * + * From the computer's perspective, every time the monitor displays + * a new frame the scanout engine has "scanned out" the display image + * from top to bottom, one row of pixels at a time. The current row + * of pixels is referred to as the current scanline. + * + * In addition to the display's visible area, there's usually a couple of + * extra scanlines which aren't actually displayed on the screen. + * These extra scanlines don't contain image data and are occasionally used + * for features like audio and infoframes. The region made up of these + * scanlines is referred to as the vertical blanking region, or vblank for + * short. + * + * For historical reference, the vertical blanking period was designed to + * give the electron gun (on CRTs) enough time to move back to the top of + * the screen to start scanning out the next frame. Similar for horizontal + * blanking periods. They were designed to give the electron gun enough + * time to move back to the other side of the screen to start scanning the + * next scanline. + * + * :: + * + * + * physical → ⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽ + * top of | | + * display | | + * | New frame | + * | | + * |↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓| + * |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| ← Scanline, + * |↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓| updates the + * | | frame as it + * | | travels down + * | | ("sacn out") + * | Old frame | + * | | + * | | + * | | + * | | physical + * | | bottom of + * vertical |⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽| ← display + * blanking ┆xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx┆ + * region → ┆xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx┆ + * ┆xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx┆ + * start of → ⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽ + * new frame + * + * "Physical top of display" is the reference point for the high-precision/ + * corrected timestamp. + * + * On a lot of display hardware, programming needs to take effect during the + * vertical blanking period so that settings like gamma, the image buffer + * buffer to be scanned out, etc. can safely be changed without showing + * any visual artifacts on the screen. In some unforgiving hardware, some of + * this programming has to both start and end in the same vblank. To help + * with the timing of the hardware programming, an interrupt is usually + * available to notify the driver when it can start the updating of registers. + * The interrupt is in this context named the vblank interrupt. + * + * The vblank interrupt may be fired at different points depending on the + * hardware. Some hardware implementations will fire the interrupt when the + * new frame start, other implementations will fire the interrupt at different + * points in time. + * * Vertical blanking plays a major role in graphics rendering. To achieve * tear-free display, users must synchronize page flips and/or rendering to * vertical blanking. The DRM API offers ioctls to perform page flips @@ -278,8 +342,8 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe, DRM_DEBUG_VBL("updating vblank count on crtc %u:" " current=%llu, diff=%u, hw=%u hw_last=%u\n", - pipe, atomic64_read(&vblank->count), diff, - cur_vblank, vblank->last); + pipe, (unsigned long long)atomic64_read(&vblank->count), + diff, cur_vblank, vblank->last); if (diff == 0) { WARN_ON_ONCE(cur_vblank != vblank->last); @@ -425,14 +489,10 @@ static void vblank_disable_fn(struct timer_list *t) spin_unlock_irqrestore(&dev->vbl_lock, irqflags); } -void drm_vblank_cleanup(struct drm_device *dev) +static void drm_vblank_init_release(struct drm_device *dev, void *ptr) { unsigned int pipe; - /* Bail if the driver didn't call drm_vblank_init() */ - if (dev->num_crtcs == 0) - return; - for (pipe = 0; pipe < dev->num_crtcs; pipe++) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; @@ -441,10 +501,6 @@ void drm_vblank_cleanup(struct drm_device *dev) del_timer_sync(&vblank->disable_timer); } - - kfree(dev->vblank); - - dev->num_crtcs = 0; } /** @@ -453,25 +509,29 @@ void drm_vblank_cleanup(struct drm_device *dev) * @num_crtcs: number of CRTCs supported by @dev * * This function initializes vblank support for @num_crtcs display pipelines. - * Cleanup is handled by the DRM core, or through calling drm_dev_fini() for - * drivers with a &drm_driver.release callback. + * Cleanup is handled automatically through a cleanup function added with + * drmm_add_action(). * * Returns: * Zero on success or a negative error code on failure. */ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs) { - int ret = -ENOMEM; + int ret; unsigned int i; spin_lock_init(&dev->vbl_lock); spin_lock_init(&dev->vblank_time_lock); + dev->vblank = drmm_kcalloc(dev, num_crtcs, sizeof(*dev->vblank), GFP_KERNEL); + if (!dev->vblank) + return -ENOMEM; + dev->num_crtcs = num_crtcs; - dev->vblank = kcalloc(num_crtcs, sizeof(*dev->vblank), GFP_KERNEL); - if (!dev->vblank) - goto err; + ret = drmm_add_action(dev, drm_vblank_init_release, NULL); + if (ret) + return ret; for (i = 0; i < num_crtcs; i++) { struct drm_vblank_crtc *vblank = &dev->vblank[i]; @@ -486,10 +546,6 @@ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs) DRM_INFO("Supports vblank timestamp caching Rev 2 (21.10.2013).\n"); return 0; - -err: - dev->num_crtcs = 0; - return ret; } EXPORT_SYMBOL(drm_vblank_init); |