Re: [Intel-gfx] [PATCH] drm/i915/display: Add a debugfs entry for fifo underruns

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 08 Feb 2023, Andi Shyti <andi.shyti@linux.intel.com> wrote:
> Hi Swati,
>
> [...]
>
>> +static void intel_fifo_underrun_inc_count(struct intel_crtc *crtc,
>> +					  bool is_cpu_fifo)
>
> I'm not a big fan of the true/false parameters in functions. I
> actually hate them because it's never clear from the caller what
> the true/false means.
>
> Isn't it clear to just have some wrappers
>
> #define intel_fifo_underrun_inc_cpu_count(...)
> #define intel_fifo_underrun_inc_cph_count(...)
>
> or similar?
>
>> +{
>> +#ifdef CONFIG_DEBUG_FS
>> +	if (is_cpu_fifo)
>> +		crtc->cpu_fifo_underrun_count++;
>> +	else
>> +		crtc->pch_fifo_underrun_count++;
>> +#endif
>> +}
>> +
>>  static void i9xx_check_fifo_underruns(struct intel_crtc *crtc)
>>  {
>>  	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
>> @@ -103,6 +114,7 @@ static void i9xx_check_fifo_underruns(struct intel_crtc *crtc)
>>  	intel_de_write(dev_priv, reg, enable_mask | PIPE_FIFO_UNDERRUN_STATUS);
>>  	intel_de_posting_read(dev_priv, reg);
>>  
>> +	intel_fifo_underrun_inc_count(crtc, true);
>>  	trace_intel_cpu_fifo_underrun(dev_priv, crtc->pipe);
>>  	drm_err(&dev_priv->drm, "pipe %c underrun\n", pipe_name(crtc->pipe));
>>  }
>> @@ -156,6 +168,7 @@ static void ivb_check_fifo_underruns(struct intel_crtc *crtc)
>>  	intel_de_write(dev_priv, GEN7_ERR_INT, ERR_INT_FIFO_UNDERRUN(pipe));
>>  	intel_de_posting_read(dev_priv, GEN7_ERR_INT);
>>  
>> +	intel_fifo_underrun_inc_count(crtc, true);
>>  	trace_intel_cpu_fifo_underrun(dev_priv, pipe);
>>  	drm_err(&dev_priv->drm, "fifo underrun on pipe %c\n", pipe_name(pipe));
>>  }
>> @@ -244,6 +257,7 @@ static void cpt_check_pch_fifo_underruns(struct intel_crtc *crtc)
>>  		       SERR_INT_TRANS_FIFO_UNDERRUN(pch_transcoder));
>>  	intel_de_posting_read(dev_priv, SERR_INT);
>>  
>> +	intel_fifo_underrun_inc_count(crtc, false);
>>  	trace_intel_pch_fifo_underrun(dev_priv, pch_transcoder);
>>  	drm_err(&dev_priv->drm, "pch fifo underrun on pch transcoder %c\n",
>>  		pipe_name(pch_transcoder));
>> @@ -286,6 +300,11 @@ static bool __intel_set_cpu_fifo_underrun_reporting(struct drm_device *dev,
>>  
>>  	old = !crtc->cpu_fifo_underrun_disabled;
>>  	crtc->cpu_fifo_underrun_disabled = !enable;
>> +#ifdef CONFIG_DEBUG_FS
>> +	/* don't reset count in fifo underrun irq path */
>> +	if (!in_irq() && !enable)
>> +		crtc->cpu_fifo_underrun_count = 0;
>> +#endif
>>  
>>  	if (HAS_GMCH(dev_priv))
>>  		i9xx_set_fifo_underrun_reporting(dev, pipe, enable, old);
>> @@ -365,6 +384,11 @@ bool intel_set_pch_fifo_underrun_reporting(struct drm_i915_private *dev_priv,
>>  
>>  	old = !crtc->pch_fifo_underrun_disabled;
>>  	crtc->pch_fifo_underrun_disabled = !enable;
>> +#ifdef CONFIG_DEBUG_FS
>> +	/* don't reset count in fifo underrun irq path */
>> +	if (!in_irq() && !enable)
>> +		crtc->pch_fifo_underrun_count = 0;
>> +#endif
>
> All these ifdefs are a bit ugly. Can we put all these stuff
> inside the debugfs.c file that is compiled only if DEBUG_FS is
> configured?

The opposite, the debugfs should be added in this file instead. :)

See my reply.

BR,
Jani.




>
> Andi
>
>>  
>>  	if (HAS_PCH_IBX(dev_priv))
>>  		ibx_set_fifo_underrun_reporting(&dev_priv->drm,
>> @@ -434,6 +458,7 @@ void intel_cpu_fifo_underrun_irq_handler(struct drm_i915_private *dev_priv,
>>  			drm_err(&dev_priv->drm, "CPU pipe %c FIFO underrun\n", pipe_name(pipe));
>>  	}
>>  
>> +	intel_fifo_underrun_inc_count(crtc, true);
>>  	intel_fbc_handle_fifo_underrun_irq(dev_priv);
>>  }

-- 
Jani Nikula, Intel Open Source Graphics Center