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committed 1e55a53a28d/* * drm_irq.c IRQ and vblank support * * \author Rickard E. (Rik) Faith <faith@valinux.com> * \author Gareth Hughes <gareth@valinux.com> * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. *//** * DOC: vblank handling * * 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 * synchronized to vertical blanking and wait for vertical blanking. * * The DRM core handles most of the vertical blanking management logic, which * involves filtering out spurious interrupts, keeping race-free blanking * counters, coping with counter wrap-around and resets and keeping use counts. * It relies on the driver to generate vertical blanking interrupts and * optionally provide a hardware vertical blanking counter. * * Drivers must initialize the vertical blanking handling core with a call to * drm_vblank_init(). Minimally, a driver needs to implement * &drm_crtc_funcs.enable_vblank and &drm_crtc_funcs.disable_vblank plus call * drm_crtc_handle_vblank() in its vblank interrupt handler for working vblank * support. * * Vertical blanking interrupts can be enabled by the DRM core or by drivers * themselves (for instance to handle page flipping operations). The DRM core * maintains a vertical blanking use count to ensure that the interrupts are not * disabled while a user still needs them. To increment the use count, drivers * call drm_crtc_vblank_get() and release the vblank reference again with * drm_crtc_vblank_put(). In between these two calls vblank interrupts are * guaranteed to be enabled. * * On many hardware disabling the vblank interrupt cannot be done in a race-free * manner, see &drm_driver.vblank_disable_immediate and * &drm_driver.max_vblank_count. In that case the vblank core only disables the * vblanks after a timer has expired, which can be configured through the * ``vblankoffdelay`` module parameter. *//* Retry timestamp calculation up to 3 times to satisfy * drm_timestamp_precision before giving up. *//* Threshold in nanoseconds for detection of redundant * vblank irq in drm_handle_vblank(). 1 msec should be ok. */static booldrm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe, ktime_t *tvblank, bool in_vblank_irq);static unsigned int drm_timestamp_precision = 20; /* Default to 20 usecs. */static int drm_vblank_offdelay = 5000; /* Default to 5000 msecs. */module_param_named(vblankoffdelay, drm_vblank_offdelay, int, 0600);module_param_named(timestamp_precision_usec, drm_timestamp_precision, int, 0600);MODULE_PARM_DESC(vblankoffdelay, "Delay until vblank irq auto-disable [msecs] (0: never disable, <0: disable immediately)");MODULE_PARM_DESC(timestamp_precision_usec, "Max. error on timestamps [usecs]");static void store_vblank(struct drm_device *dev, unsigned int pipe,