linux-kernel - Re: [RFC PATCH v3 2/4] ufs: core: mcq: Adds Multi-Circular Queue support

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Date:   Wed, 7 Sep 2022 20:01:36 -0700
From:   "Asutosh Das (asd)" <quic_asutoshd@...cinc.com>
To:     Bean Huo <huobean@...il.com>, <quic_nguyenb@...cinc.com>,
        <quic_xiaosenh@...cinc.com>, <stanley.chu@...iatek.com>,
        <adrian.hunter@...el.com>, <bvanassche@....org>,
        <avri.altman@....com>, <mani@...nel.org>, <quic_cang@...cinc.com>,
        <beanhuo@...ron.com>, <martin.petersen@...cle.com>,
        <linux-scsi@...r.kernel.org>
CC:     <linux-arm-msm@...r.kernel.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Jinyoung Choi <j-young.choi@...sung.com>,
        Kiwoong Kim <kwmad.kim@...sung.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v3 2/4] ufs: core: mcq: Adds Multi-Circular Queue
 support

Hello Bean
Thanks for your comments. Responses inline.

On 9/5/2022 9:27 AM, Bean Huo wrote:
> On Fri, 2022-09-02 at 15:41 -0700, Asutosh Das wrote:
>>
>> +
>> +static void ufshcd_mcq_config_nr_queues(struct ufs_hba *hba)
>> +{
>> +       int i, rem;
>> +       u32 hbaq_cap, cmp;
>> +       struct Scsi_Host *host = hba->host;
>> +
>> +       hbaq_cap = hba->mcq_capabilities & 0xff;
>> +
>> +       rem = hbaq_cap - dev_cmd_queue;
>> +       /* min() compares variables of same type */
>> +       hba->nr_queues[HCTX_TYPE_DEFAULT] = min(hbaq_cap -
>> dev_cmd_queue,
> 
>   hba->nr_queues[HCTX_TYPE_DEFAULT] = min(rem, num_possible_cpus());
> 
min() compares variables of same type only.
>> +                                               num_possible_cpus());
>> +       rem -= hba->nr_queues[HCTX_TYPE_DEFAULT];
>> +       if (rem <= 0)
>> +               goto out;
>> +       cmp = rem;
>> +       hba->nr_queues[HCTX_TYPE_POLL] = min(cmp, poll_queues);
>> +       rem -= hba->nr_queues[HCTX_TYPE_POLL];
>> +       if (rem <= 0)
>> +               goto out;
>> +       cmp = rem;
>> +       hba->nr_queues[HCTX_TYPE_READ] = min(cmp, read_queues);
> 
> static read_queues is not initialized.
> 
It would be initialized to 0. But I think we should configure it as a 
module parameter which is missing. Let me add it in the next version.
>>
> .....
>> +static inline void ufshcd_inc_tp(struct ufs_hw_queue *q)
>> +{
>> +       u32 mask = q->max_entries - 1;
>> +       u32 val;
>> +
>> +       q->sq_tp_slot = (q->sq_tp_slot + 1) & mask;
>> +       val = q->sq_tp_slot * sizeof(struct utp_transfer_req_desc);
>> +       writel(val, q->mcq_sq_tp);
>> +}
> 
> This function just accesses the submission queue tail pointer. The
> function name should clearly explain this.
> 
The reason for this naming was that only SQ's tail pointer can be 
updated by SW. I can add a _sq_ to this function in the next version. 
Plmk if you prefer a better name.

> 
> 
>