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

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Message-ID: <83142b0c-0743-4a23-8846-e9f5e72a7677@kernel.org>
Date: Tue, 9 Dec 2025 06:53:45 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Aaron Kling <webgeek1234@...il.com>
Cc: Jon Hunter <jonathanh@...dia.com>, Rob Herring <robh@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Thierry Reding
 <thierry.reding@...il.com>, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH v4 3/5] memory: tegra186-emc: Support non-bpmp icc scaling

On 09/12/2025 05:26, Aaron Kling wrote:
> On Sat, Nov 22, 2025 at 6:01 AM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>>
>> On 21/11/2025 12:21, Jon Hunter wrote:
>>>
>>> On 12/11/2025 07:21, Aaron Kling wrote:
>>>> On Wed, Nov 12, 2025 at 12:18 AM Jon Hunter <jonathanh@...dia.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 ..
> 
> With this patch dropped from -next, what needs to happen to get it
> requeued? I gave an analysis over two weeks ago and have seen no
> response since.

Hm, I did not see the root cause identified, so maybe I missed something.

Anyway, I am waiting for the patchset to be retested and resent. And
testing MUST include kernel development process rules, including how
patches are taken - see maintainer soc profile. Any dependencies must be
clearly marked.

Best regards,
Krzysztof