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

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Message-ID: <b9373252-710c-4a54-95cc-046314796960@quicinc.com>
Date:   Wed, 6 Dec 2023 19:32:54 +0530
From:   Naresh Maramaina <quic_mnaresh@...cinc.com>
To:     Bart Van Assche <bvanassche@....org>,
        "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 12/5/2023 10:41 PM, Bart Van Assche wrote:
> 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?

IMHO, instead of completely removing this flag, how about having
flag like "UFSHCD_CAP_DISABLE_PM_QOS" which will make PMQOS enable
by default and if some host vendor wants to disable it explicitly,
they can enable that flag.
Please let me know your opinion.

>>>
>>>> + * @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'.

Sure. I'll take of this in next patchset.

> 
> Thanks,
> 
> Bart.
> 

Thanks,
Naresh