linux-kernel - Re: [PATCH v5 5/5] PCI: qcom: Use frequency and level based OPP lookup

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Message-ID: <ozlhnzkzwwifwhqn54ja5xqndtyjf35nbjnsidl5nn6xe3eijf@ptzzqchq2kwq>
Date: Fri, 31 Oct 2025 11:58:56 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>, 
	Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Lorenzo Pieralisi <lpieralisi@...nel.org>, 
	Krzysztof Wilczyński <kwilczynski@...nel.org>, Rob Herring <robh@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v5 5/5] PCI: qcom: Use frequency and level based OPP
 lookup

On Wed, Oct 29, 2025 at 03:39:48PM -0500, Bjorn Helgaas wrote:
> On Mon, Oct 13, 2025 at 04:23:32PM +0530, Krishna Chaitanya Chundru wrote:
> > PCIe link configurations such as 8GT/s x2 and 16GT/s x1 may operate at
> > the same frequency but differ in other characteristics like RPMh votes.
> > The existing OPP selection based solely on frequency cannot distinguish
> > between such cases.
> > 
> > In such cases, frequency alone is insufficient to identify the correct OPP.
> > Use the newly introduced dev_pm_opp_find_key_exact() API to match both
> > frequency and level when selecting an OPP, here level indicates PCIe
> > data rate.
> > 
> > To support older device tree's where opp-level is not defined, check if
> > opp-level is present or not using dev_pm_opp_find_level_exact(). if
> > not present fallback to frequency only match.
> 
> What are the names of the DT properties here for the exact (frequency
> + level) and frequency-only values?  I'd like to mention them in the
> commit log so we can look at a DT and figure out what to expect from
> this change.

Frequency: opp-hz
Level: opp-level

- Mani

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