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drm/i915/ddi: Guard reg_val against a INVALID_TRANSCODER

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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: 6671c367a9 ("drm/i915/tgl: Select master transcoder for MST stream")
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://lore.kernel.org/r/20250908042208.1011144-1-suraj.kandpal@intel.com
(cherry picked from commit c8e8e9ab14a6ea926641d161768e1e3ef286a853)
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>
This commit is contained in:
Suraj Kandpal
2025-09-23 08:52:18 +01:00
committed by Tvrtko Ursulin
parent c1e7254935
commit 7f97a0a871
1 changed files with 3 additions and 2 deletions
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drivers/gpu/drm/i915/display/intel_ddi.c
+3 -2
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@@ -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 {