[PATCH] drm/i915/display: Add link rate and lane count to i915_display_info

[Jani Nikula]

On Tue, 18 Mar 2025, Khaled Almahallawy <khaled.almahallawy at intel.com> wrote:
> Adding link rate and lane count information to i915_display_info makes it
> easier and faster to access this data compared to checking kernel logs.
> This is particularly beneficial for individuals who are not familiar with
> i915 in the following scenarios:
>
> * Debugging DP tunnel bandwidth usage in the Thunderbolt driver.
> * During USB4 certification, it is necessary to know the link rate used by
>   the monitor to prove that the DP tunnel can handle required rates.
> * In PHY CTS, when the connector probes are not mounted correctly,
>   some display lanes may not appear in the DP Oscilloscope, leading to CTS
>   failures.
>
> This change provides validation teams with an easy way to identify and
> troubleshoot issues.
>
> Cc: Imre Deak <imre.deak at intel.com>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Signed-off-by: Khaled Almahallawy <khaled.almahallawy at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display_debugfs.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> index fdedf65bee53..bda7751472e2 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> @@ -551,9 +551,10 @@ static void intel_crtc_info(struct seq_file *m, struct intel_crtc *crtc)
>  	seq_printf(m, "\tpipe__mode=" DRM_MODE_FMT "\n",
>  		   DRM_MODE_ARG(&crtc_state->hw.pipe_mode));
>  
> -	seq_printf(m, "\tpipe src=" DRM_RECT_FMT ", dither=%s, bpp=%d\n",
> +	seq_printf(m, "\tpipe src=" DRM_RECT_FMT ", dither=%s, bpp=%d, port_clock=%d, lane_count=%d\n",
>  		   DRM_RECT_ARG(&crtc_state->pipe_src),
> -		   str_yes_no(crtc_state->dither), crtc_state->pipe_bpp);
> +		   str_yes_no(crtc_state->dither), crtc_state->pipe_bpp,
> +		   crtc_state->port_clock, crtc_state->lane_count);

Maybe deserves to be a separate line instead of bundling it with pipe
src etc?

Also, lane_count is bound to be 0 for a lot of outputs where it's
irrelevant.

BR,
Jani.

>  
>  	intel_scaler_info(m, crtc);

-- 
Jani Nikula, Intel