Re: [PATCH v2 1/2] drm/i915/mso: using joiner is not possible with eDP MSO

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

On Fri, 14 Jun 2024, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Fri, Jun 14, 2024 at 01:16:03PM +0300, Jani Nikula wrote:
>> It's not possible to use the joiner at the same time with eDP MSO. When
>> a panel needs MSO, it's not optional, so MSO trumps joiner.
>> 
>> While just reporting false for intel_dp_has_joiner() should be
>> sufficient, also skip creation of the joiner force enable debugfs to
>> better handle this in testing.
>> 
>> Cc: stable@vger.kernel.org
>> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
>> Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/1668
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_display_debugfs.c | 8 ++++++--
>>  drivers/gpu/drm/i915/display/intel_dp.c              | 4 ++++
>>  2 files changed, 10 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 91757fed9c6d..5eb31404436c 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
>> +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
>> @@ -1546,8 +1546,12 @@ void intel_connector_debugfs_add(struct intel_connector *connector)
>>  	if (DISPLAY_VER(i915) >= 11 &&
>>  	    (connector_type == DRM_MODE_CONNECTOR_DisplayPort ||
>>  	     connector_type == DRM_MODE_CONNECTOR_eDP)) {
>> -		debugfs_create_bool("i915_bigjoiner_force_enable", 0644, root,
>> -				    &connector->force_bigjoiner_enable);
>> +		struct intel_dp *intel_dp = intel_attached_dp(connector);
>
> That won't give you anything on MST.

Gah!

> Dunno if there's any point in
> trying to do anything here anyway. We don't account for the other
> intel_dp_has_joiner() restrictions here either.

The only point would be skipping a bunch of IGT tests. With the debugfs
in place, kms_big_joiner thinks it enables joiner, and runs extra joiner
tests for nothing.

Thoughts? I guess the simplest fix for stable could be just the last
hunk here.

BR,
Jani.


>
>> +
>> +		/* eDP MSO is not compatible with joiner */
>> +		if (!intel_dp->mso_link_count)
>> +			debugfs_create_bool("i915_bigjoiner_force_enable", 0644, root,
>> +					    &connector->force_bigjoiner_enable);
>>  	}
>>  
>>  	if (connector_type == DRM_MODE_CONNECTOR_DSI ||
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index 9a9bb0f5b7fe..ab33c9de393a 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -465,6 +465,10 @@ bool intel_dp_has_joiner(struct intel_dp *intel_dp)
>>  	struct intel_encoder *encoder = &intel_dig_port->base;
>>  	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
>>  
>> +	/* eDP MSO is not compatible with joiner */
>> +	if (intel_dp->mso_link_count)
>> +		return false;
>> +
>
> This part looks fine.
>
>>  	return DISPLAY_VER(dev_priv) >= 12 ||
>>  		(DISPLAY_VER(dev_priv) == 11 &&
>>  		 encoder->port != PORT_A);
>> -- 
>> 2.39.2

-- 
Jani Nikula, Intel