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

[Asutosh Das (asd)]

Hello Bean
Thanks for your comments. Responses inline.

On 9/5/2022 6:48 AM, Bean Huo wrote:
> 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.
Correct. The spec is fuzzy about it. Because ext_iid provides a 
provision to increase the Queue depth to 2^12. Even though the 
parameters that you referred to don't support it now.

Will remove this part in the next version.

> Kind regards,
> Bean