[PATCH] imx: Revert "imx: mx6ull: fix REFTOP_VBGADJ setting" and fix comments

[Fabio Estevam]

Hi Emanuele,

On Thu, Nov 6, 2025 at 7:22 AM Emanuele Ghidoli
<ghidoliemanuele at gmail.com> wrote:

> Hi Fabio, Ye,
>
> At Toradex we have been struggling since quite some time (back to 2018) with

Does this problem only affect early i.MX6ULL silicon samples?

> the temperature readings and the thermal shutdown behavior on i.MX6ULL. The
> issue we observed is that the thermal shutdown seems to trigger too early.
>
> I have investigated the history around this topic and verified some internal
> notes in our bug tracker. With this revert applied, and on the devices we have
> (all trimmed with value 0), the reported temperature increases by about 10 °C
> compared to before the revert. The absolute accuracy of the readout is
> questionable: for example, on a device kept at around 20 °C, the temperature
> readout was ~19 °C before the revert, and ~31 °C after the revert.
>
> Consider that for devices with fuse value of 6, there is a -10 degrees offset
> after this revert (so, the other way around).
>
> I understand that for Sven this revert improves stability during large XZ
> decompression in userspace for few devices, but for us it means that the
> thermal shutdown happens roughly 10 °C earlier, which is a serious issue in
> our case.
>
> I would kindly ask NXP to double-check how these devices were trimmed. My gut
> feeling is that there might be an inconsistency, either the trimming scheme is
> not backward-compatible (e.g. old and new devices behave differently, and the
> code should cope, I don't know how, with this), or this patch must be reverted
> (because introduces a regression).

Peng/Ye Li,

How does NXP suggest we handle this? Were the early i.MX6ULL parts
incorrectly fused?

Can the fuse be read and dynamically adjusted?

Please advise, thanks.