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

[Emanuele Ghidoli]

On 19/11/2025 08:49, Ye Li wrote:
> Hi Michael, Emanuele,
> 
> On 11/12/2025 6:07 PM, Michael Nazzareno Trimarchi wrote:
>> Hi all
>>
>> On Wed, Nov 12, 2025 at 10:57 AM Emanuele Ghidoli
>> <ghidoliemanuele at gmail.com> wrote:
>>>
>>>
>>>
>>> On 12/11/2025 09:16, Ye Li wrote:
>>>>
>>>>
>>>> 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.
>>> It could take a little to answer to the first two question. I can say that the
>>> SoM I'm using to validate the patch was assembled in September 2021. Let me
>>> know if this information are needed giving that I can report the marking on
>>> the chip:
>>> MCIMX6Y2CVM08AB CTDQ2107 1N70S CHINA QGDQCTA
>>>
>>>
>>>>
>>>>>
>>>>>> 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".
>>> Colibri iMX6ULL # fuse read 0 0 1
>>> Reading bank 0:
>>>
>>> Word 0x00000000: 00320003
>>> Colibri iMX6ULL # fuse read 1 0 1
>>> Reading bank 1:
>>>
>>> Word 0x00000000: 00000080
>>>
>>
>> As is clear this problem was the same we had some months ago, so we
>> are on the same page
>> with Emanuele
>>
>> Michael
>>
> 
> 
> Can you help to measure the VDD_ARM_CAP and VDD_SOC_CAP on your devices with
> high temperature read issue, when REFTOP_VBGADJ is set to 3'b000 and 3'b110
> respectively. Provide the measured voltage and target voltage.
> And please read the Unique ID fuse of this device by "fuse read 0 1 2".
Running u-boot, VDD_ARM_CAP and VDD_SOC_CAP respectively:
- With REFTOP_VBGADJ set to b000: 1.08 V and 1.11 V
- With REFTOP_VBGADJ set to b110: 1.06 V and 1.08 V

Best regards,
Emanuele>
> 
> Best regards,
> Ye Li
> 
>>> Kind regards,
>>> Emanuele
>>>
>>>>
>>>> Best regards,
>>>> Ye Li
>>>>> Please advise, thanks.
>>>>
>>>
>>
>>
>