[PATCH i-g-t v4] tests/kms_tiled_display: Skip if connectors are not of same type

[Nautiyal, Ankit K]

On 6/3/2025 10:47 AM, Pranay Samala wrote:
> Tiled display setups require all involved DP connectors to be of the
> same type. This patch adds a check to skip the test when
> connector types differ, preventing invalid configurations and reducing
> confusing test failures.

If I understand correctly, the real problem is that when working with 
tiled monitors in IGT tests, each tile of a monitor appears as a 
separate DRM connector.

To perform a coordinated modeset on a tiled display, it's necessary to 
group connectors that belong to the same physical monitor.

However, a challenge arises when:

Multiple identical monitors (same make and model) are connected.

Each monitor reports the same tile_group_id, num_h_tile, and num_v_tile. 
The tile positions (e.g., (0,0) and (1,0)) are identical across monitors.

This leads to ambiguity: it's impossible to determine which (0,0) tile 
belongs with which (1,0) tile.

In one of the test platform there are two dummy HDMI and DP dummy plugs 
are connected which advertise as a tiled displays :

https://intel-gfx-ci.01.org/tree/intel-xe/xe-3043-842c3c276c106040f9b96d72b9df35ed6aed9ae9/shard-dg2-464/igt@kms_tiled_display@basic-test-pattern.html

The test seems to be getting one tile from DP and other from HDMI. In 
this particular case, atleast the connector type check can help.

So I agree to the change to alteast get tiles from connectors of same 
type, but the real problems still persists, and I am not very sure how 
to deal with this.

Another possible solution would be to restrict the test to DisplayPort 
connectors, since tiled display is supported only over DisplayPort.

With that said, it would be good to mention the problem clearly that the 
patch is trying to fix.


Regards,

Ankit

>
> v2: Replace igt_assert with igt_skip_on_f to skip the test.
> v3: Edit port sync supported in commit message (Ankit)
>      Check if connector type is DRM_MODE_CONNECTOR_Unknown (Ankit)
> v4: Remove connector_type check
>
> Signed-off-by: Pranay Samala <pranay.samala at intel.com>
> ---
>   tests/kms_tiled_display.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/tests/kms_tiled_display.c b/tests/kms_tiled_display.c
> index 1f5331408..a1b7f90d1 100644
> --- a/tests/kms_tiled_display.c
> +++ b/tests/kms_tiled_display.c
> @@ -165,10 +165,17 @@ static void get_connectors(data_t *data)
>   		}
>   
>   		/* Check if the connectors belong to the same tile group */
> -		if (count > 0)
> +		if (count > 0) {
>   			igt_assert(conns[count].tile.tile_group_id ==
>   				   conns[count-1].tile.tile_group_id);
>   
> +			igt_skip_on_f(conns[count - 1].connector->connector_type !=
> +				      conns[count].connector->connector_type,
> +				      "Connector type mismatch: Expected %d, but got %d\n",
> +				      conns[count - 1].connector->connector_type,
> +				      conns[count].connector->connector_type);
> +		}
> +
>   		count++;
>   	}
>   	igt_require_f(count == data->num_h_tiles,