Re: [PATCH] drm/i915: Make vblank evade warnings optional

On Sun, May 07, 2017 at 08:12:52PM +0300, ville.syrjala@linux.intel.com wrote:

From: Ville Syrjälä ville.syrjala@linux.intel.com

Add a new Kconfig option to enable/disable the extra warnings from the vblank evade code. For now we'll keep the warning about an actually missed vblank always enabled as that can have an actual user visible impact. But if we miss the deadline othrwise there's no real need to bother the user with that. We'll want these warnings enabled during development however so that we can catch regressions.

Based on the reports it looks like this is still very easy to hit on SKL, so we have more work ahead of us to optimize the crtiical section further.

Cc: Daniel Vetter daniel@ffwll.ch Cc: Jani Nikula jani.nikula@linux.intel.com Cc: Dave Airlie airlied@redhat.com Cc: Jens Axboe axboe@kernel.dk Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Maarten Lankhorst maarten.lankhorst@linux.intel.com Reported-by: Jens Axboe axboe@kernel.dk Reported-by: Linus Torvalds torvalds@linux-foundation.org Fixes: e1edbd44e23b ("drm/i915: Complain if we take too long under vblank evasion.") Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com

Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

---

drivers/gpu/drm/i915/Kconfig.debug | 13 +++++++++++++ drivers/gpu/drm/i915/intel_sprite.c | 7 +++++-- 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig.debug b/drivers/gpu/drm/i915/Kconfig.debug index e091809a9a9e..49db32fa6524 100644 --- a/drivers/gpu/drm/i915/Kconfig.debug +++ b/drivers/gpu/drm/i915/Kconfig.debug @@ -87,3 +87,16 @@ config DRM_I915_LOW_LEVEL_TRACEPOINTS and also analyze the request dependency resolving timeline.

       If in doubt, say "N".

+config DRM_I915_DEBUG_VBLANK_EVADE

• bool "Enable extra debug warnings for vblank evasion"
• depends on DRM_I915
• default n
• help

•  Choose this option to turn on extra debug warnings for the
  

•  vblank evade mechanism. This gives a warning every time the
  

•  the deadline allotted for the vblank evade critical section
  

•  is exceeded, even if there isn't an actual risk of missing
  

•  the vblank.
  

•  If in doubt, say "N".
  

diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c index f7d431427115..8c87c717c7cd 100644 --- a/drivers/gpu/drm/i915/intel_sprite.c +++ b/drivers/gpu/drm/i915/intel_sprite.c @@ -198,12 +198,15 @@ void intel_pipe_update_end(struct intel_crtc *crtc, struct intel_flip_work *work ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time), crtc->debug.min_vbl, crtc->debug.max_vbl, crtc->debug.scanline_start, scanline_end);

• } else if (ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time) >

•    VBLANK_EVASION_TIME_US)
  

• }

+#ifdef CONFIG_DRM_I915_DEBUG_VBLANK_EVADE

• else if (ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time) >

•  VBLANK_EVASION_TIME_US)
  

  DRM_WARN("Atomic update on pipe (%c) took %lld us, max time under evasion is %u us\n", pipe_name(pipe), ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time), VBLANK_EVASION_TIME_US);

+#endif }

static void

2.10.2