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

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Message-ID: <20251029203948.GA1585122@bhelgaas>
Date: Wed, 29 Oct 2025 15:39:48 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Cc: Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
	Stephen Boyd <sboyd@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Manivannan Sadhasivam <mani@...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 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.