Re: [PATCH v4 3/5] memory: tegra186-emc: Support non-bpmp icc scaling

Krzysztof Kozlowski
2025-11-12T07:26:36Z

On 12/11/2025 07:18, Jon Hunter wrote:
>
> On 11/11/2025 23:17, Aaron Kling wrote:
>
> ...
>
>> Alright, I think I've got the picture of what's going on now. The
>> standard arm64 defconfig enables the t194 pcie driver as a module. And
>> my simple busybox ramdisk that I use for mainline regression testing
>> isn't loading any modules. If I set the pcie driver to built-in, I
>> replicate the issue. And I don't see the issue on my normal use case,
>> because I have the dt changes as well.
>>
>> So it appears that the pcie driver submits icc bandwidth. And without
>> cpufreq submitting bandwidth as well, the emc driver gets a very low
>> number and thus sets a very low emc freq. The question becomes... what
>> to do about it? If the related dt changes were submitted to
>> linux-next, everything should fall into place. And I'm not sure where
>> this falls on the severity scale since it doesn't full out break boot
>> or prevent operation.
>
> Where are the related DT changes? If we can get these into -next and
> lined up to be merged for v6.19, then that is fine. However, we should

It's still breaking all the users then.

> not merge this for v6.19 without the DT changes.
>
> I will also talk with Thierry to see if he has any concerns about users
> seeing slow performance if they don't have an up-to-date DTB.
>
> Is there any easy way to detect if the DTB has he necessary properties
> to enable ICC scaling?
>
> Jon
>

Best regards,
Krzysztof