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

Jon Hunter
2025-11-12T06:18:19Z

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
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

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nvpublic