Re: [PATCH v3 4/6] drm/i915/lobf: Add debug interface for lobf

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

On Wed, 08 Jan 2025, "Hogander, Jouni" <jouni.hogander@intel.com> wrote:
> On Mon, 2025-01-06 at 09:45 +0530, Animesh Manna wrote:
>> Add an interface in debugfs which will help in debugging LOBF
>> feature.
>>
>> 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    |  6 +++
>>  2 files changed, 57 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c
>> b/drivers/gpu/drm/i915/display/intel_alpm.c
>> index 197c67363f0e..1cc0e5ed3f74 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 &
>> I915_LOBF_DEBUG_DISABLE)
>> +             return;
>> +
>>       if (!intel_dp_is_edp(intel_dp))
>>               return;
>>
>> @@ -448,6 +451,51 @@ 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;
>> +     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.
>> +             *val = READ_ONCE(intel_dp-
>> >alpm_parameters.lobf_debug);
>> +             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;
>> +}
>> +
>> +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);
>> @@ -457,6 +505,9 @@ 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 f230163226d1..37f061acb204 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
>> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
>> @@ -1800,6 +1800,12 @@ struct intel_dp {
>>               u8 aux_less_wake_lines;
>>               u8 silence_period_sym_clocks;
>>               u8 lfps_half_cycle_num_of_syms;
>> +
>> +#define I915_LOBF_DEBUG_MODE_MASK            0x0f
>> +#define I915_LOBF_DEBUG_DEFAULT                      0x00
>> +#define I915_LOBF_DEBUG_DISABLE                      0x01
>> +#define I915_LOBF_DEBUG_FORCE_EN             0x02
>
> FORCE_EN is not needed. You can achieve LOBF (if it's possible) by
> disabling PSR/PR.

To be honest, I don't like adding these debug mode masks at all. Don't
make it so complicated. Moreover, the only user of any of these is

	intel_dp->alpm_parameters.lobf_debug & I915_LOBF_DEBUG_DISABLE

but lobf_debug is *boolean*!

Keep it simple.

And "i915" naming in display code is discouraged, unless it's in
reference to i915 as the platform.

BR,
Jani.


>
> BR,
>
> Jouni Högander
>
>> +             bool lobf_debug;
>>       } alpm_parameters;
>>
>>       u8 alpm_dpcd;
>

-- 
Jani Nikula, Intel