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Message-ID: <f3f3329b-0dc9-4652-9f23-d55852f046d8@quicinc.com>
Date: Mon, 19 Feb 2024 12:32:52 +0530
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Subject: Re: [PATCH v6 5/6] arm64: dts: qcom: sm8450: Add opp table support to
 PCIe
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To: Konrad Dybcio <konrad.dybcio@linaro.org>,
        Viresh Kumar
	<viresh.kumar@linaro.org>
CC: Manivannan Sadhasivam <mani@kernel.org>,
        Bjorn Andersson
	<andersson@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        "Lorenzo
 Pieralisi" <lpieralisi@kernel.org>,
        =?UTF-8?Q?Krzysztof_Wilczy=c5=84ski?=
	<kw@linux.com>,
        Rob Herring <robh@kernel.org>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.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>,
        <vireshk@kernel.org>, <quic_vbadigan@quicinc.com>,
        <quic_skananth@quicinc.com>, <quic_nitegupt@quicinc.com>,
        <linux-pci@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <20240112-opp_support-v6-5-77bbf7d0cc37@quicinc.com>
 <20240129160420.GA27739@thinkpad>
 <20240130061111.eeo2fzaltpbh35sj@vireshk-i7>
 <20240130071449.GG32821@thinkpad>
 <20240130083619.lqbj47fl7aa5j3k5@vireshk-i7>
 <20240130094804.GD83288@thinkpad>
 <20240130095508.zgufudflizrpxqhy@vireshk-i7> <20240130131625.GA2554@thinkpad>
 <20240131052335.6nqpmccgr64voque@vireshk-i7>
 <610d5d7c-ec8d-42f1-81a2-1376b8a1a43f@linaro.org>
 <20240202073334.mkabgezwxn3qe7iy@vireshk-i7>
 <8a7b63a8-0583-43cf-9876-8a964c8b77ee@linaro.org>
From: Krishna Chaitanya Chundru <quic_krichai@quicinc.com>
In-Reply-To: <8a7b63a8-0583-43cf-9876-8a964c8b77ee@linaro.org>
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On 2/10/2024 2:44 AM, Konrad Dybcio wrote:
> On 2.02.2024 08:33, Viresh Kumar wrote:
>> On 01-02-24, 15:45, Konrad Dybcio wrote:
>>> I'm lukewarm on this.
>>>
>>> A *lot* of hardware has more complex requirements than "x MBps at y MHz",
>>> especially when performance counters come into the picture for dynamic
>>> bw management.
>>>
>>> OPP tables can't really handle this properly.
>>
>> There was a similar concern for voltages earlier on and we added the capability
>> of adjusting the voltage for OPPs in the OPP core. Maybe something similar can
>> be done here ?
>>
> I really don't think it's fitting.. At any moment the device may require any
> bandwidth value between 0 and MAX_BW_PER_LINK_GEN * LINK_WIDTH..
> 
> Konrad
Viresh & konrad can you both come to conclusion on this.

- Krishna Chaitanya.