From: Suraj Kandpal Date: Mon, 8 Sep 2025 04:22:08 +0000 (+0530) Subject: drm/i915/ddi: Guard reg_val against a INVALID_TRANSCODER X-Git-Tag: v6.17~18^2~2^2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7f97a0a871d9532f2e1a5ee7d16d0e364215bcac;p=thirdparty%2Fkernel%2Fstable.git drm/i915/ddi: Guard reg_val against a INVALID_TRANSCODER Currently we check if the encoder is INVALID or -1 and throw a WARN_ON but we still end up writing the temp value which will overflow and corrupt the whole programmed value. --v2 -Assign a bogus transcoder to master in case we get a INVALID TRANSCODER [Jani] Fixes: 6671c367a9bea ("drm/i915/tgl: Select master transcoder for MST stream") Signed-off-by: Suraj Kandpal Reviewed-by: Jani Nikula Link: https://lore.kernel.org/r/20250908042208.1011144-1-suraj.kandpal@intel.com (cherry picked from commit c8e8e9ab14a6ea926641d161768e1e3ef286a853) Signed-off-by: Tvrtko Ursulin --- diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c index 0405396c7750e..9ecbb4b99c378 100644 --- a/drivers/gpu/drm/i915/display/intel_ddi.c +++ b/drivers/gpu/drm/i915/display/intel_ddi.c @@ -596,8 +596,9 @@ intel_ddi_transcoder_func_reg_val_get(struct intel_encoder *encoder, enum transcoder master; master = crtc_state->mst_master_transcoder; - drm_WARN_ON(display->drm, - master == INVALID_TRANSCODER); + if (drm_WARN_ON(display->drm, + master == INVALID_TRANSCODER)) + master = TRANSCODER_A; temp |= TRANS_DDI_MST_TRANSPORT_SELECT(master); } } else {