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

[Ye Li]

On 11/11/2025 9:47 PM, Fabio Estevam wrote:
> 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?
Hi Emanuele,

     I have same question as Fabio. Are these samples are early? Do you 
know the time of receiving these sample? And could you show the part 
number printed on the chip.

> 
>> 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?
I need to discuss it internally, will feedback you later.

> 
> Can the fuse be read and dynamically adjusted?
>
The fuse is locked by MEM_TRIM_LOCK. Emanuele, can you help to read it 
by "fuse read 0 0 1".

Best regards,
Ye Li
> Please advise, thanks.