drm/i915/alpm: Check for alpm support before accessing alpm register

Currently, only EDP supports alpm.  So, check for alpm support and prevent
the DP connector from accessing the alpm register if doing so is unsupported.

Fixes: acff6d6bded3 ("drm/i915/lobf: Add mutex for alpm update")
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://lore.kernel.org/r/20250425132107.2926759-1-animesh.manna@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c b/drivers/gpu/drm/i915/display/intel_alpm.c
index 482dd192d47dd3260e7acaee7d6f3de56f3aedc6..1bf08b80c23f9a99318cec4dcdd2eeffaad9426d 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_alpm.c
+++ b/drivers/gpu/drm/i915/display/intel_alpm.c
@@ -556,7 +556,7 @@ void intel_alpm_disable(struct intel_dp *intel_dp)
        struct intel_display *display = to_intel_display(intel_dp);
        enum transcoder cpu_transcoder = intel_dp->alpm_parameters.transcoder;
 
-       if (DISPLAY_VER(display) < 20)
+       if (DISPLAY_VER(display) < 20 || !intel_dp->alpm_dpcd)
                return;
 
        mutex_lock(&intel_dp->alpm_parameters.lock);