Claude review: Re: [PATCH 3/6] drm/msm/dp: Limit voltage swing level to 2 for RA620 bridge

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**This patch has a serious problem: it changes a global constant.**

```c
-#define DP_TRAIN_LEVEL_MAX	3
+#define DP_TRAIN_LEVEL_MAX	2
```

`DP_TRAIN_LEVEL_MAX` is used throughout the MSM DP driver for *all* DP connections:

- `dp_ctrl.c`: Determines when `DP_TRAIN_MAX_SWING_REACHED` is signaled to the sink
- `dp_link.c`: Clamps voltage swing and pre-emphasis levels; calculates `max_p_level = DP_TRAIN_LEVEL_MAX - v_level`

The DP specification defines voltage swing levels 0-3. Level 3 (1200 mV) is a valid, in-spec operating point. Some monitors and bridges legitimately require level 3 to establish a link. Capping the global maximum at 2 will break those configurations on all Qualcomm DP platforms — not just the Radxa Dragon Q6A.

**Recommendation**: This needs to be a per-bridge or per-platform quirk, not a global constant change. Options include:
1. A device tree property on the DP node specifying the max voltage swing level
2. A quirk based on the connected bridge's identity (though the RA620 is passive and has no identity)
3. A platform-specific override in the board DTS that the DP driver reads

The commit message correctly identifies the problem (RA620 doesn't complete link training at level 3) but the fix has too broad a blast radius.

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