linux-kernel - Re: [PATCH v6 6/6] PCI: qcom: Add OPP support to scale performance state of power domain

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Message-ID: <20240112165010.GA2271863@bhelgaas>
Date: Fri, 12 Jan 2024 10:50:10 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Johan Hovold <johan+linaro@...nel.org>,
	Brian Masney <bmasney@...hat.com>,
	Georgi Djakov <djakov@...nel.org>, linux-arm-msm@...r.kernel.org,
	vireshk@...nel.org, quic_vbadigan@...cinc.com,
	quic_skananth@...cinc.com, quic_nitegupt@...cinc.com,
	linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 6/6] PCI: qcom: Add OPP support to scale performance
 state of power domain

On Fri, Jan 12, 2024 at 07:52:05PM +0530, Krishna chaitanya chundru wrote:
> QCOM Resource Power Manager-hardened (RPMh) is a hardware block which
> maintains hardware state of a regulator by performing max aggregation of
> the requests made by all of the processors.
> 
> PCIe controller can operate on different RPMh performance state of power
> domain based up on the speed of the link. And this performance state varies
> from target to target.
> 
> It is manadate to scale the performance state based up on the PCIe speed
> link operates so that SoC can run under optimum power conditions.
> 
> Add Operating Performance Points(OPP) support to vote for RPMh state based
> upon GEN speed link is operating.

Thanks for this "OPP" expansion!  Maybe "GEN" is unnecessary in this
sentence?  And below, could be replaced with actual speeds?

> OPP can handle ICC bw voting also, so move icc bw voting through opp
> framework if opp entries are present.

s/opp/OPP/ to match
s/icc/ICC/ similarly (and perhaps expand once)
Also below in comments, etc.

> In PCIe certain gen speeds like GEN1x2 & GEN2X1 or GEN3x2 & GEN4x1 use
> same icc bw and has frequency, so use frequency based search to reduce
> number of entries in the opp table.
> 
> Don't initialize icc if opp is supported.

Bjorn