forked from Minki/linux
8f6fce03dd
A change in locking of some kms drivers (currently intel-kms) make the old approach too inaccurate and also incompatible with the PREEMPT_RT realtime kernel patchset. The driver->get_scanout_position() method of intel-kms now needs to aquire a spinlock, which clashes badly with the former preempt_disable() calls in the drm, and it also introduces larger delays and timing uncertainty on a contended lock than acceptable. This patch changes the prototype of driver->get_scanout_position() to require/allow kms drivers to perform the ktime_get() system time queries which go along with actual scanout position readout in a way that provides maximum precision and to return those timestamps to the drm. kms drivers implementations of get_scanout_position() are asked to implement timestamping and scanoutpos readout in a way that is as precise as possible and compatible with preempt_disable() on a PREMPT_RT kernel. A driver should follow this pattern in get_scanout_position() for precision and compatibility: spin_lock...(...); preempt_disable_rt(); // On a PREEMPT_RT kernel, otherwise omit. if (stime) *stime = ktime_get(); ... Minimum amount of MMIO register reads to get scanout position ... ... no taking of locks allowed here! ... if (etime) *etime = ktime_get(); preempt_enable_rt(); // On PREEMPT_RT kernel, otherwise omit. spin_unlock...(...); v2: Fix formatting of new multi-line code comments. Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Alex Deucher <alexander.deucher@amd.com> Signed-off-by: Dave Airlie <airlied@redhat.com> |
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.. | ||
i2c | ||
ttm | ||
drm_agpsupport.h | ||
drm_buffer.h | ||
drm_cache.h | ||
drm_core.h | ||
drm_crtc_helper.h | ||
drm_crtc.h | ||
drm_dp_helper.h | ||
drm_edid.h | ||
drm_encoder_slave.h | ||
drm_fb_cma_helper.h | ||
drm_fb_helper.h | ||
drm_fixed.h | ||
drm_flip_work.h | ||
drm_gem_cma_helper.h | ||
drm_global.h | ||
drm_hashtab.h | ||
drm_mem_util.h | ||
drm_memory.h | ||
drm_mm.h | ||
drm_os_linux.h | ||
drm_pciids.h | ||
drm_rect.h | ||
drm_sysfs.h | ||
drm_usb.h | ||
drm_vma_manager.h | ||
drmP.h | ||
exynos_drm.h | ||
gma_drm.h | ||
i915_drm.h | ||
i915_pciids.h | ||
i915_powerwell.h | ||
intel-gtt.h |