Re: [Intel-gfx] [PATCH 2/2] drm/i915/display/debug: Expose Dither status via debugfs

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

On Wed, 26 May 2021, Bhanuprakash Modem <bhanuprakash.modem@intel.com> wrote:
> It's useful to know the dithering state & pipe bpc for IGT testing.
> This patch will expose the dithering state for the crtc via a debugfs
> file "dither".
>
> Example usage: cat /sys/kernel/debug/dri/0/crtc-0/dither
>
> Cc: Uma Shankar <uma.shankar@intel.com>
> Cc: Nischal Varide <nischal.varide@intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Signed-off-by: Bhanuprakash Modem <bhanuprakash.modem@intel.com>
> ---
>  .../drm/i915/display/intel_display_debugfs.c  | 32 +++++++++++++++++++
>  1 file changed, 32 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> index 94e5cbd86e77..a6fefc7d5ab9 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> @@ -2158,11 +2158,43 @@ static const struct {
>  	{"i915_edp_psr_debug", &i915_edp_psr_debug_fops},
>  };
>  
> +static int dither_state_show(struct seq_file *m, void *data)
> +{
> +	struct intel_crtc *crtc = to_intel_crtc(m->private);
> +	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> +	struct intel_crtc_state *crtc_state;
> +	int ret;
> +
> +	if (!HAS_DISPLAY(dev_priv))
> +		return -ENODEV;

Unneeded.

> +
> +	ret = drm_modeset_lock_single_interruptible(&crtc->base.mutex);
> +	if (ret)
> +		return ret;
> +
> +	crtc_state = to_intel_crtc_state(crtc->base.state);
> +	seq_printf(m, "bpc: %u\n", crtc_state->pipe_bpp / 3);
> +	seq_printf(m, "Dither: %u\n", (crtc_state->dither) ? 1 : 0);
> +	seq_printf(m, "Dither_CC1: %u\n",
> +		(crtc_state->gamma_mode & GAMMA_MODE_DITHER_AFTER_CC1) ? 1 : 0);

Are you looking to duplicate the conditions for enabling this CC1 mode
in IGT, and then checking if the driver set the bit as well?

I thought the direction has been that we don't do this type of
validation in IGT. There is no end to it.

Ville?

> +
> +	drm_modeset_unlock(&crtc->base.mutex);
> +
> +	return 0;
> +}
> +DEFINE_SHOW_ATTRIBUTE(dither_state);
> +
>  void intel_display_debugfs_register(struct drm_i915_private *i915)
>  {
>  	struct drm_minor *minor = i915->drm.primary;
> +	struct drm_device *dev = &i915->drm;
> +	struct drm_crtc *crtc;
>  	int i;
>  
> +	drm_for_each_crtc(crtc, dev)
> +		debugfs_create_file("dither", 0444, crtc->debugfs_entry, crtc,
> +				    &dither_state_fops);
> +

See intel_crtc_debugfs_add(), called from intel_crtc_late_register().

>  	for (i = 0; i < ARRAY_SIZE(intel_display_debugfs_files); i++) {
>  		debugfs_create_file(intel_display_debugfs_files[i].name,
>  				    S_IRUGO | S_IWUSR,

-- 
Jani Nikula, Intel Open Source Graphics Center
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