linux-kernel - Re: [PATCH v12 6/6] PCI: qcom: Add OPP support to scale performance

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Date: Tue, 14 May 2024 11:28:38 +0200
From: Manivannan Sadhasivam <mani@...nel.org>
To: Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, johan+linaro@...nel.org,
	bmasney@...hat.com, djakov@...nel.org,
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	vireshk@...nel.org, quic_vbadigan@...cinc.com,
	quic_skananth@...cinc.com, quic_nitegupt@...cinc.com,
	quic_parass@...cinc.com, krzysztof.kozlowski@...aro.org
Subject: Re: [PATCH v12 6/6] PCI: qcom: Add OPP support to scale performance

On Thu, May 09, 2024 at 09:21:55PM +0530, Krishna Chaitanya Chundru wrote:
> 
> 
> On 4/30/2024 10:56 AM, Manivannan Sadhasivam wrote:
> > On Sat, Apr 27, 2024 at 07:22:39AM +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 clients.
> > > 
> > > PCIe controller can operate on different RPMh performance state of power
> > > domain based on the speed of the link. And this performance state varies
> > > from target to target, like some controllers support GEN3 in NOM (Nominal)
> > > voltage corner, while some other supports GEN3 in low SVS (static voltage
> > > scaling).
> > > 
> > > The SoC can be more power efficient if we scale the performance state
> > > based on the aggregate PCIe link bandwidth.
> > > 
> > > Add Operating Performance Points (OPP) support to vote for RPMh state based
> > > on the aggregate link bandwidth.
> > > 
> > > OPP can handle ICC bw voting also, so move ICC bw voting through OPP
> > > framework if OPP entries are present.
> > > 
> > > As we are moving ICC voting as part of OPP, don't initialize ICC if OPP
> > > is supported.
> > > 
> > > Before PCIe link is initialized vote for highest OPP in the OPP table,
> > > so that we are voting for maximum voltage corner for the link to come up
> > > in maximum supported speed.
> > > 
> > > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> > > ---
> > >   drivers/pci/controller/dwc/pcie-qcom.c | 81 ++++++++++++++++++++++++++++------
> > >   1 file changed, 67 insertions(+), 14 deletions(-)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > > index 465d63b4be1c..40c875c518d8 100644
> > > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > 
> > [...]
> > 
> > > @@ -1661,6 +1711,9 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
> > >   		ret = icc_disable(pcie->icc_cpu);
> > >   		if (ret)
> > >   			dev_err(dev, "Failed to disable CPU-PCIe interconnect path: %d\n", ret);
> > > +
> > > +		if (!pcie->icc_mem)
> > > +			dev_pm_opp_set_opp(pcie->pci->dev, NULL);
> > 
> > At the start of the suspend, there is a call to icc_set_bw() for PCIe-MEM path.
> > Don't you want to update it too?
> > 
> > - Mani
> > 
> if opp is supported we just need to call dev_pm_opp_set_opp() only once
> which will take care for both PCIe-MEM & CPU-PCIe path.
> so we are not adding explicitly there.

No, I was asking you why you are not adding a check for the existing
icc_set_bw() at the start like you were doing elsewhere.

- Mani

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