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

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Date:   Mon, 05 Sep 2022 15:48:15 +0200
From:   Bean Huo <huobean@...il.com>
To:     Asutosh Das <quic_asutoshd@...cinc.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

On Fri, 2022-09-02 at 15:41 -0700, Asutosh Das wrote:
> +/**
> + * ufshcd_mcq_decide_queue_depth - decide the queue depth
> + * @hba - per adapter instance
> + *
> + * MAC - Max. Active Command of the Host Controller (HC)
> + * HC wouldn't send more than this commands to the device.
> + * The default MAC is 32, but the max. value may vary with
> + * vendor implementation.
> + * Calculates and adjusts the queue depth based on the depth
> + * supported by the HC, ufs device and if ext_iid is supported.
> + */
> +u32 ufshcd_mcq_decide_queue_depth(struct ufs_hba *hba)
> +{
> +       u32 qd, val;
> +       int mac;
> +
> +       mac = ufshcd_mcq_vops_get_hba_mac(hba);
> +       if (mac < 0) {
> +               val = ufshcd_readl(hba, REG_UFS_MCQ_CFG);
> +               mac = (val & MCQ_CFG_MAC_MASK) >> MCQ_CFG_MAC_OFFSET;
> +       }
> +
> +       /*  MAC is a 0 based value. */
> +       mac += 1;
> +       qd = min_t(u32, mac, hba->dev_info.bqueuedepth);
> +       if (!qd)
> +               qd = mac;
> +
> +       /* Adjust queue depth based on ext_iid support. */
> +       if (qd > 256 && (!hba->ext_iid_sup || !hba-
> >dev_info.b_ext_iid_en))
> +               qd = 256;
> +       else if (qd > 4096 && hba->ext_iid_sup && hba-
> >dev_info.b_ext_iid_en)
> +               qd = 4096;
> +

Astosh,

I don't understand here.  How can qd be 4096?  MAC in UFSHCI  is 9 bits
width, the maximum depth will be 512, and hba->dev_info.bqueuedepth is
one byte width, maximum will be 256.

Kind regards,
Bean