From: Bjorn Helgaas <helgaas@kernel.org>
To: Krishna chaitanya chundru <quic_krichai@quicinc.com>
Cc: "Bjorn Andersson" <andersson@kernel.org>,
"Konrad Dybcio" <konrad.dybcio@linaro.org>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
"Rob Herring" <robh@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
"Conor Dooley" <conor+dt@kernel.org>,
"Manivannan Sadhasivam" <manivannan.sadhasivam@linaro.org>,
"Rob Herring" <robh+dt@kernel.org>,
"Johan Hovold" <johan+linaro@kernel.org>,
"Brian Masney" <bmasney@redhat.com>,
"Georgi Djakov" <djakov@kernel.org>,
linux-arm-msm@vger.kernel.org, linux-pci@vger.kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
vireshk@kernel.org, quic_vbadigan@quicinc.com,
quic_skananth@quicinc.com, quic_nitegupt@quicinc.com,
quic_parass@quicinc.com
Subject: Re: [PATCH v7 7/7] PCI: qcom: Add OPP support to scale performance state of power domain
Date: Tue, 27 Feb 2024 17:36:36 -0600 [thread overview]
Message-ID: <20240227233636.GA250826@bhelgaas> (raw)
In-Reply-To: <20240223-opp_support-v7-7-10b4363d7e71@quicinc.com>
On Fri, Feb 23, 2024 at 08:18:04PM +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 up on the speed of the link. And this performance state varies
> from target to target.
s/up on/on/ (or "upon" if you prefer) (also below)
I understand changing the performance state based on the link speed,
but I don't understand the variation from target to target. Do you
mean just that the link speed may vary based on the rates supported by
the downstream device?
> 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.
It sounds like it's more power efficient, but not actually
*mandatory*. Maybe something like this?
The SoC can be more power efficient if we scale the performance
state based on the aggregate PCIe link speed.
> Add Operating Performance Points(OPP) support to vote for RPMh state based
> upon the speed link is operating.
Space before open paren, e.g., "Points (OPP)".
"... based on the link speed."
> OPP can handle ICC bw voting also, so move ICC bw voting through OPP
> framework if OPP entries are present.
>
> In PCIe certain speeds like GEN1x2 & GEN2x1 or GEN3x2 & GEN4x1 use
> same bw and frequency and thus the OPP entry, so use frequency based
> search to reduce number of entries in the OPP table.
GEN1x2, GEN2x1, etc are not "speeds". I would say:
Different link configurations may share the same aggregate speed,
e.g., a 2.5 GT/s x2 link and a 5.0 GT/s x1 link have the same speed
and share the same OPP entry.
> Don't initialize ICC if OPP is supported.
Because? Maybe this should say something about OPP including the ICC
voting?
> + ret = icc_set_bw(pcie->icc_mem, 0, width * QCOM_PCIE_LINK_SPEED_TO_BW(speed));
Wrap to fit in 80 columns.
> + * Use highest OPP here if the OPP table is present. At the end of the probe(),
> + * OPP will be updated using qcom_pcie_icc_opp_update().
Wrap to fit in 80 columns.
> + /* Skip ICC init if OPP is supported as ICC bw vote is handled by OPP framework */
Wrap to fit in 80 columns.
next prev parent reply other threads:[~2024-02-27 23:36 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-23 14:47 [PATCH v7 0/7] PCI: qcom: Add support for OPP Krishna chaitanya chundru
2024-02-23 14:47 ` [PATCH v7 1/7] dt-bindings: PCI: qcom: Add interconnects path as required property Krishna chaitanya chundru
2024-02-23 14:47 ` [PATCH v7 2/7] arm64: dts: qcom: sm8450: Add interconnect path to PCIe node Krishna chaitanya chundru
2024-02-23 14:48 ` [PATCH v7 3/7] PCI: qcom: Add ICC bandwidth vote for CPU to PCIe path Krishna chaitanya chundru
2024-02-24 0:02 ` Konrad Dybcio
2024-02-27 3:14 ` Krishna Chaitanya Chundru
2024-02-27 23:22 ` Bjorn Helgaas
2024-02-28 6:38 ` Krishna Chaitanya Chundru
2024-02-28 13:39 ` Johan Hovold
2024-02-28 15:13 ` Krishna Chaitanya Chundru
2024-02-28 15:33 ` Bjorn Helgaas
2024-02-28 14:50 ` Bjorn Helgaas
2024-02-28 15:11 ` Krishna Chaitanya Chundru
2024-02-23 14:48 ` [PATCH v7 4/7] dt-bindings: pci: qcom: Add opp table Krishna chaitanya chundru
2024-02-23 14:48 ` [PATCH v7 5/7] arm64: dts: qcom: sm8450: Add opp table support to PCIe Krishna chaitanya chundru
2024-02-23 14:48 ` [PATCH v7 6/7] PCI: Bring out the pcie link speed to MBps logic to new function Krishna chaitanya chundru
2024-02-28 0:25 ` Bjorn Helgaas
2024-02-28 6:47 ` Krishna Chaitanya Chundru
2024-02-23 14:48 ` [PATCH v7 7/7] PCI: qcom: Add OPP support to scale performance state of power domain Krishna chaitanya chundru
2024-02-27 23:36 ` Bjorn Helgaas [this message]
2024-02-27 23:45 ` Bjorn Helgaas
2024-02-28 6:48 ` Krishna Chaitanya Chundru
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