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

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Message-ID: <f0cf2f70-f2b4-47b2-b6d8-358e36c750e7@nvidia.com>
Date: Wed, 12 Nov 2025 10:59:31 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, Aaron Kling <webgeek1234@...il.com>
Cc: 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 12/11/2025 07:26, Krzysztof Kozlowski wrote:
> 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.

Yes indeed.

Jon

-- 
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