Re: [PATCH] drm/panel-edp: Change BOE NV153WUM-N42 enable timings

[Doug Anderson]

Hi,

On Wed, Apr 1, 2026 at 2:03 AM Alvin1 Chen
<alvin1.chen@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> BOE: NV153WUM-N42
> 00 ff ff ff ff ff ff 00 09 e5 b3 0d 00 00 00 00
> 11 23 01 04 a5 21 15 78 03 af e5 97 5e 58 92 28
> 1f 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01
> 01 01 01 01 01 01 9c 3e 80 c8 70 b0 3c 40 30 20
> 36 00 49 ce 10 00 00 1a 00 00 00 fd 00 28 3c 4c
> 4c 10 01 0a 20 20 20 20 20 20 00 00 00 fe 00 42
> 4f 45 20 43 51 0a 20 20 20 20 20 20 00 00 00 fc
> 00 4e 56 31 35 33 57 55 4d 2d 4e 34 32 0a 01 92
>
> 70 20 79 02 00 81 00 15 74 1a 00 00 03 01 28 3c
> 00 00 60 49 60 49 3c 00 00 00 00 80 00 00 00 00
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 cb 90

NOTE: EDID is only needed here if it's different from the EDID that
was provided when the panel was first added.


> The default 80ms enable delay (T8) for the BOE NV153WUM-N42 panel
> has been found to be insufficient for certain hardware units,
> leading to intermittent display initialization failures and
> "drmSetMaster failed with -1" errors during VT2 switching.
>
> Through extensive stress testing, increasing the '.enable' delay
> to 200ms provides a **significant improvement** in synchronization
> reliability. While this adjustment may not completely eliminate
> failures on marginal hardware units, it substantially reduces the
> failure rate and provides a more robust timing margin for the
> DRM driver to complete initialization.
>
> Validation:
> On a previously failing unit, the 200ms delay demonstrated a
> marked improvement in stability, successfully passing over 1,200
> cold boot cycles before a failure was observed. This is a
> significant leap in reliability compared to the original 80ms
> generic setting.

I'm really not a fan. Is there a way to determine the deeper root
cause here? Have you asked BOE about what's going on here? Do they
understand why the panel needs this extra delay, and why even with the
extra delay it still doesn't always work? Is the problem truly related
to the panel, or somehow about how it's hooked up to the board? I'm
just worried that this is papering over the real bug by pushing around
timings and the bug will come back again at some random time in the
future.


-Doug