ci/lava: Use UART for non-Chromebooks

Some Chromebooks have unreliable UART, so we fall back to SSH for them.
However, SSH setup adds a 10-15s overhead, so we now restrict its usage
to devices with the "depthcharge" boot method (i.e., Chromebooks).

Signed-off-by: Valentine Burley <valentine.burley@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35936>

.gitlab-ci/image-tags.yml

@@ -30,7 +30,7 @@ variables:
 
   ALPINE_X86_64_BUILD_TAG: "20250709-libwayland"
   ALPINE_X86_64_LAVA_SSH_TAG: "20250423-rootfs"
-  ALPINE_X86_64_LAVA_TRIGGER_TAG: "20250619-cts-ovl"
+  ALPINE_X86_64_LAVA_TRIGGER_TAG: "20250701-uart"
 
   FEDORA_X86_64_BUILD_TAG: "20250709-libwayland"
 

.gitlab-ci/lava/utils/lava_farm.py

@@ -18,3 +18,16 @@ def get_lava_farm() -> str:
         logging.warning("FARM environment variable is not set, using unknown")
 
     return farm.lower()
+
+def get_lava_boot_method() -> str:
+    """
+    Returns the LAVA boot method based on the BOOT_METHOD environment variable.
+
+    :return: The LAVA boot method
+    """
+    boot_method: str = os.getenv("BOOT_METHOD", "unknown")
+
+    if boot_method == "unknown":
+        logging.warning("BOOT_METHOD environment variable is not set, using unknown")
+
+    return boot_method.lower()

.gitlab-ci/lava/utils/lava_job_definition.py

@@ -11,7 +11,7 @@ from ruamel.yaml import YAML
 
 from os import getenv
 
-from lava.utils.lava_farm import get_lava_farm
+from lava.utils.lava_farm import get_lava_farm, get_lava_boot_method
 from lava.utils.log_section import LAVA_DEPLOY_TIMEOUT
 from lava.utils.ssh_job_definition import (
     generate_docker_test,
@@ -60,11 +60,15 @@ class LAVAJobDefinition:
         if FORCE_UART:
             return False
 
-        # Only Collabora's farm supports to run docker container as a LAVA actions,
-        # which is required to follow the job in a SSH section
         current_farm = get_lava_farm()
+        boot_method = get_lava_boot_method()
 
-        return current_farm == "collabora"
+        # Some Chromebooks have unreliable serial connections, so SSH is preferred.
+        # Only Collabora's farm supports running docker container as a LAVA actions,
+        # which is required to follow the job in an SSH section
+        # Chromebooks use the "depthcharge" boot method, so use SSH in that case,
+        # and UART for everything else.
+        return current_farm == "collabora" and boot_method == "depthcharge"
 
     def generate_lava_yaml_payload(self) -> dict[str, Any]:
         """

.gitlab-ci/tests/utils/test_lava_job_definition.py

@@ -85,8 +85,9 @@ def clear_env_vars(autouse=True):
 
 @pytest.fixture
 def mock_collabora_farm(clear_env_vars, monkeypatch):
-    # Mock a Collabora farm-like device runner tag to enable SSH execution
+    # Mock a Chromebook in the Collabora farm
     monkeypatch.setenv("FARM", "collabora")
+    monkeypatch.setenv("BOOT_METHOD", "depthcharge")
 
 
 @pytest.mark.parametrize("force_uart", [True, False], ids=["SSH", "UART"])