linux-kernel - Re: [PATCH V2 1/3] ufs: core: Add CPU latency QoS support for ufs driver

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Message-ID: <5e7c5c75-cb5f-4afe-9d57-b0cab01a6f26@acm.org>
Date:   Tue, 5 Dec 2023 07:11:56 -1000
From:   Bart Van Assche <bvanassche@....org>
To:     Naresh Maramaina <quic_mnaresh@...cinc.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Peter Wang <peter.wang@...iatek.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>, chu.stanley@...il.com
Cc:     Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, quic_cang@...cinc.com,
        quic_nguyenb@...cinc.com, Nitin Rawat <quic_nitirawa@...cinc.com>
Subject: Re: [PATCH V2 1/3] ufs: core: Add CPU latency QoS support for ufs
 driver

On 12/4/23 21:58, Naresh Maramaina wrote:
> On 12/5/2023 12:30 AM, Bart Van Assche wrote:
>> On 12/4/23 06:30, Maramaina Naresh wrote:
>>> +    /* This capability allows the host controller driver to use the 
>>> PM QoS
>>> +     * feature.
>>> +     */
>>> +    UFSHCD_CAP_PM_QOS                = 1 << 13,
>>>   };
>>
>> Why does it depend on the host driver whether or not PM QoS is
>> enabled? Why isn't it enabled unconditionally?
> 
> For some platform vendors power KPI might be more important than random 
> io KPI. Hence this flag is disabled by default and can be enabled based 
> on platform requirement.

How about leaving this flag out unless if a host vendor asks explicitly
for this flag?
>>
>>> + * @pm_qos_req: PM QoS request handle
>>> + * @pm_qos_init: flag to check if pm qos init completed
>>>    */
>>
>> Documentation for pm_qos_init is missing.
>>
> Sorry, i didn't get your comment, i have already added documentation for 
> @pm_qos_init, @pm_qos_req variable as above. Do you want me to add this 
> information some where else as well?

Oops, I meant 'qos_vote'.

Thanks,

Bart.