linux-kernel - Re: [PATCH v2 0/3] phy: qcom-qmp-pcie: Add support to keep refclk always on

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Date:   Thu, 9 Nov 2023 14:57:58 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Krishna Chaitanya Chundru <quic_krichai@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_vbadigan@...cinc.com, quic_ramkri@...cinc.com,
        quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
        quic_vpernami@...cinc.com, quic_parass@...cinc.com
Subject: Re: [PATCH v2 0/3] phy: qcom-qmp-pcie: Add support to keep refclk
 always on



On 11/9/23 10:32, Krishna Chaitanya Chundru wrote:
> 
> On 11/8/2023 3:27 AM, Konrad Dybcio wrote:
>>
>>
>> On 11/7/23 13:26, Krishna chaitanya chundru wrote:
>>> This series adds support to provide refclk to endpoint even in low
>>> power states.
>>>
>>> Due to some platform specific issues with CLKREQ signal, it is not being
>>> propagated to the host and as host doesn't know the clkreq signal host is
>>> not sending refclk. Due to this endpoint is seeing linkdown and going
>>> to bad state.
>>> To avoid those ref clk should be provided always to the endpoint. The
>>> issue is coming only when ep intiates the L1.1 or L1.2 exit and clkreq
>>> is not being propagated properly to the host.
>> I'm gonna sound like a broken record, but:
>>
>> How much power does this consume? Would it matter if we kept this
>> clock always-on for all platforms with this version of the phy?
>>
>> Konrad
> 
> We see about 22mw extra power consumption with refclk always on.
> 
> We can't keep this property always on as there is impact on power consumption.
Ooeheh, that's not far away from a low-clocked efficiency CPU core..

Thanks for checking!

Konrad