Passing 0 as the step only works when there are other reasons to break
out of the BPP loop in intel_dp_mtp_tu_compute_config(). Otherwise, an
infinite loop might occur. Fix it by explicitly checking for 0 step.

Fixes: ef0a0757bbea ("drm/i915/dp: compute config for 128b/132b SST w/o DSC")
Reported-by: Imre Deak <[email protected]>
Closes: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jani Nikula <[email protected]>

---

Note: This needs a backport with (!step) for -rc1.
---
 drivers/gpu/drm/i915/display/intel_dp_mst.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c 
b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 95abc6ea85eb..1587be5cd0a7 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -353,6 +353,10 @@ int intel_dp_mtp_tu_compute_config(struct intel_dp 
*intel_dp,
 
                        break;
                }
+
+               /* Allow using zero step to indicate one try */
+               if (!bpp_step_x16)
+                       break;
        }
 
        if (slots < 0) {
-- 
2.39.5

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