Re: [PATCH v4 5/8] drm/i915/lobf: Add debug interface for lobf

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

On Mon, 24 Feb 2025, Animesh Manna <animesh.manna@intel.com> wrote:
> Add an interface in debugfs which will help in debugging LOBF
> feature.
>
> v1: Initial version.
> v2:
> - Remove FORCE_EN flag. [Jouni]
> - Change prefix from I915 to INTEL. [Jani]
> - Use u8 instead of bool for lobf-debug flag. [Jani]
>
> Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_alpm.c     | 51 +++++++++++++++++++
>  .../drm/i915/display/intel_display_types.h    |  5 ++
>  2 files changed, 56 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c b/drivers/gpu/drm/i915/display/intel_alpm.c
> index 83719ee1721c..5c70677ac3c0 100644
> --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> +++ b/drivers/gpu/drm/i915/display/intel_alpm.c
> @@ -276,6 +276,9 @@ void intel_alpm_lobf_compute_config(struct intel_dp *intel_dp,
>  	int waketime_in_lines, first_sdp_position;
>  	int context_latency, guardband;
>  
> +	if (intel_dp->alpm_parameters.lobf_debug & INTEL_LOBF_DEBUG_DISABLE)
> +		return;
> +
>  	if (!intel_dp_is_edp(intel_dp))
>  		return;
>  
> @@ -449,6 +452,51 @@ static int i915_edp_lobf_info_show(struct seq_file *m, void *data)
>  
>  DEFINE_SHOW_ATTRIBUTE(i915_edp_lobf_info);
>  
> +static int
> +i915_edp_lobf_debug_get(void *data, u64 *val)
> +{
> +	struct intel_display *display = data;

Where do you pass display as data? It's connector?

> +	struct intel_encoder *encoder;
> +	int ret = -ENODEV;
> +
> +	for_each_intel_dp(display->drm, encoder) {
> +		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> +
> +		if (!intel_dp_is_edp(intel_dp))
> +			return ret;

What is this supposed to do?

> +
> +		// TODO: split to each edp transcoder.

What does this mean?

> +		*val = READ_ONCE(intel_dp->alpm_parameters.lobf_debug);

You read this from all intel_dp and combine into one? What?

> +		ret = 0;
> +	}
> +
> +	return ret;
> +}
> +
> +static int
> +i915_edp_lobf_debug_set(void *data, u64 val)
> +{
> +	struct intel_display *display = data;
> +	struct intel_encoder *encoder;
> +	int ret = -ENODEV;
> +
> +	for_each_intel_dp(display->drm, encoder) {
> +		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> +
> +		if (!intel_dp_is_edp(intel_dp))
> +			return ret;
> +
> +		// TODO: split to each edp transcoder.
> +		intel_dp->alpm_parameters.lobf_debug = val;
> +	}
> +
> +	return ret;

So this always returns failure?

> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(i915_edp_lobf_debug_fops,
> +			i915_edp_lobf_debug_get, i915_edp_lobf_debug_set,
> +			"%llu\n");
> +
>  void intel_alpm_lobf_debugfs_add(struct intel_connector *connector)
>  {
>  	struct intel_display *display = to_intel_display(connector);
> @@ -458,6 +506,9 @@ void intel_alpm_lobf_debugfs_add(struct intel_connector *connector)
>  	    connector->base.connector_type != DRM_MODE_CONNECTOR_eDP)
>  		return;
>  
> +	debugfs_create_file("i915_edp_lobf_debug", 0644, root,
> +			    connector, &i915_edp_lobf_debug_fops);
> +
>  	debugfs_create_file("i915_edp_lobf_info", 0444, root,
>  			    connector, &i915_edp_lobf_info_fops);
>  }
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index b78721c451b8..b6ec9a8fadd9 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1808,6 +1808,11 @@ struct intel_dp {
>  		u8 aux_less_wake_lines;
>  		u8 silence_period_sym_clocks;
>  		u8 lfps_half_cycle_num_of_syms;
> +
> +#define INTEL_LOBF_DEBUG_MODE_MASK		0x0f
> +#define INTEL_LOBF_DEBUG_DEFAULT		0x00
> +#define INTEL_LOBF_DEBUG_DISABLE		0x01
> +		u8 lobf_debug;

Just overly complex still.

>  	} alpm_parameters;
>  
>  	u8 alpm_dpcd;

-- 
Jani Nikula, Intel