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

Jon Hunter
2025-11-21T11:21:28Z

On 12/11/2025 07:21, Aaron Kling wrote:
> On Wed, Nov 12, 2025 at 12:18 AM Jon Hunter <jonathanh@nvidia.com> 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
>> not merge this for v6.19 without the DT changes.
>
> The dt changes are here [0].

To confirm, applying the DT changes do not fix this for me. Thierry is
having a look at this to see if there is a way to fix this.

BTW, I have also noticed that Thierry's memory frequency test [0] is
also failing on Tegra186. The test simply tries to set the frequency via
the sysfs and this is now failing. I am seeing ...

memory: emc: - available rates: (* = current)
memory: emc: - 40800000
memory: emc: - 68000000
memory: emc: - 102000000
memory: emc: - 204000000
memory: emc: - 408000000
memory: emc: - 665600000
memory: emc: - 800000000
memory: emc: - 1062400000
memory: emc: - 1331200000
memory: emc: - 1600000000
memory: emc: - 1866000000 *
memory: emc: - testing:
memory: emc: - 40800000...OSError: [Errno 34] Numerical result out
of range

Jon

[0] https://github.com/thierryreding/tegra-tests

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