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ad3543ede6
Move the ktime_get() clock readouts and potential preempt_disable()
calls from drm core into kms driver to make it compatible with the
api changes in the drm core.
The intel-kms driver needs to take the uncore.lock inside
i915_get_crtc_scanoutpos() and intel_pipe_in_vblank().
This is incompatible with the preempt_disable() on a
PREEMPT_RT patched kernel, as regular spin locks must not
be taken within a preempt_disable'd section. Lock contention
on the uncore.lock also introduced too much uncertainty in vblank
timestamps.
Push the ktime_get() timestamping for scanoutpos queries and
potential preempt_disable_rt() into i915_get_crtc_scanoutpos(),
so these problems can be avoided:
1. First lock the uncore.lock (might sleep on a PREEMPT_RT kernel).
2. preempt_disable_rt() (will be added by the rt-linux folks).
3. ktime_get() a timestamp before scanout pos query.
4. Do all mmio reads as fast as possible without grabbing any new locks!
5. ktime_get() a post-query timestamp.
6. preempt_enable_rt()
7. Unlock the uncore.lock.
This reduces timestamp uncertainty on a low-end HP Atom Mini netbook
with Intel GMA-950 nicely:
Before: 3-8 usecs with spikes > 20 usecs, triggering query retries.
After : Typically 1 usec (98% of all samples), occassionally 2 usecs
(2% of all samples), with maximum of 3 usecs (a handful).
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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| .. | ||
| dvo_ch7xxx.c | ||
| dvo_ch7017.c | ||
| dvo_ivch.c | ||
| dvo_ns2501.c | ||
| dvo_sil164.c | ||
| dvo_tfp410.c | ||
| dvo.h | ||
| i915_debugfs.c | ||
| i915_dma.c | ||
| i915_drv.c | ||
| i915_drv.h | ||
| i915_gem_context.c | ||
| i915_gem_debug.c | ||
| i915_gem_dmabuf.c | ||
| i915_gem_evict.c | ||
| i915_gem_execbuffer.c | ||
| i915_gem_gtt.c | ||
| i915_gem_stolen.c | ||
| i915_gem_tiling.c | ||
| i915_gem.c | ||
| i915_gpu_error.c | ||
| i915_ioc32.c | ||
| i915_irq.c | ||
| i915_reg.h | ||
| i915_suspend.c | ||
| i915_sysfs.c | ||
| i915_trace_points.c | ||
| i915_trace.h | ||
| i915_ums.c | ||
| intel_acpi.c | ||
| intel_bios.c | ||
| intel_bios.h | ||
| intel_crt.c | ||
| intel_ddi.c | ||
| intel_display.c | ||
| intel_dp.c | ||
| intel_drv.h | ||
| intel_dsi_cmd.c | ||
| intel_dsi_cmd.h | ||
| intel_dsi_pll.c | ||
| intel_dsi.c | ||
| intel_dsi.h | ||
| intel_dvo.c | ||
| intel_fbdev.c | ||
| intel_hdmi.c | ||
| intel_i2c.c | ||
| intel_lvds.c | ||
| intel_modes.c | ||
| intel_opregion.c | ||
| intel_overlay.c | ||
| intel_panel.c | ||
| intel_pm.c | ||
| intel_ringbuffer.c | ||
| intel_ringbuffer.h | ||
| intel_sdvo_regs.h | ||
| intel_sdvo.c | ||
| intel_sideband.c | ||
| intel_sprite.c | ||
| intel_tv.c | ||
| intel_uncore.c | ||
| Kconfig | ||
| Makefile | ||