Re: [PATCH 2/2] drm/i915: Complain if we take too long under vblank evasion.

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 01-03-17 om 16:40 schreef Ville Syrjälä:
> On Tue, Feb 28, 2017 at 03:28:48PM +0100, Maarten Lankhorst wrote:
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_sprite.c | 12 ++++++++++--
>>  1 file changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
>> index 27e0752d1578..375ca91b308c 100644
>> --- a/drivers/gpu/drm/i915/intel_sprite.c
>> +++ b/drivers/gpu/drm/i915/intel_sprite.c
>> @@ -65,6 +65,8 @@ int intel_usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
>>  			    1000 * adjusted_mode->crtc_htotal);
>>  }
>>  
>> +#define VBLANK_EVASION_TIME_US 100
>> +
>>  /**
>>   * intel_pipe_update_start() - start update of a set of display registers
>>   * @crtc: the crtc of which the registers are going to be updated
>> @@ -92,7 +94,8 @@ void intel_pipe_update_start(struct intel_crtc *crtc)
>>  		vblank_start = DIV_ROUND_UP(vblank_start, 2);
>>  
>>  	/* FIXME needs to be calibrated sensibly */
>> -	min = vblank_start - intel_usecs_to_scanlines(adjusted_mode, 100);
>> +	min = vblank_start - intel_usecs_to_scanlines(adjusted_mode,
>> +						      VBLANK_EVASION_TIME_US);
>>  	max = vblank_start - 1;
>>  
>>  	local_irq_disable();
>> @@ -191,7 +194,12 @@ 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)
>> +		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);
> Hmm. Yeah this should make it very likely that we'll catch any
> potential fails even when they don't happen to hit the actual critical
> section. Hopefully it won't result in massive amounts of noise. One way
> to find out ;)
>
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Thanks, pushed. Also added a commit message to this commit.
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