Re: [PATCH 1/2] scsi: ufs: Add Multi-Circular Queue support

[Asutosh Das (asd)]

On 7/24/2022 2:54 PM, Bean Huo wrote:
> Hi Can/Asutosh
>
> A few questions about MCQ configuration:

Hello Bean,
Thanks for the review.

> On Tue, 2022-07-19 at 00:01 -0700, Can Guo wrote:
> > From: Asutosh Das <quic_asutoshd@xxxxxxxxxxx>
> >
> > Adds MCQ support to UFS driver.
> >
> > Co-developed-by: Can Guo <quic_cang@xxxxxxxxxxx>
> > Signed-off-by: Asutosh Das <quic_asutoshd@xxxxxxxxxxx>
> > Signed-off-by: Can Guo <quic_cang@xxxxxxxxxxx>
> > ---
> >
> > +void ufshcd_mcq_config_mac(struct ufs_hba *hba)
> > +{
> > +       u32 val = ufshcd_readl(hba, REG_UFS_MCQ_CFG);
> > +
> > +       val &= ~MCQ_CFG_MAC_MASK;
> > +       val |= hba->dev_info.bqueuedepth << MCQ_CFG_MAC_OFFSET;
> > +       ufshcd_writel(hba, val, REG_UFS_MCQ_CFG);
>
> Here you set MaxActiveCommand to dev_info.bqueuedepth (this limit comes
> from UFS devices). I see in the qsize configuration that you want to
> set the queue depth in each HW queue to be hba->nutrs (this limit comes
> from UFSHCI),  should not it be min(device limit, ufshci limit)?
Yes, looks like it should be. Let me relook this logic.
> > +}
> > +EXPORT_SYMBOL_GPL(ufshcd_mcq_config_mac);
> > +
> ...
> > +
> > +       for_each_hw_queue(hba, i) {
> > +               hwq = &hba->uhq[i];
> > +               hwq->id = i;
> > +               qsize = hwq->max_entries * MCQ_ENTRY_SIZE_IN_DWORD -
> > 1;
>
> qsize is hba->nutrs, 32*8-1 = 255 =256DW,  per draft spec , should not
> be 8DW in 4.0?
>
> > +
> > +               /* SQLBA */
> > +               ufsmcq_writel(hba, lower_32_bits(hwq->sqe_dma_addr),
> > +                             MCQ_CFG_n(REG_SQLBA, i));
> > +               /* SQUBA */
> > +               ufsmcq_writel(hba, upper_32_bits(hwq->sqe_dma_addr),
> > +                             MCQ_CFG_n(REG_SQUBA, i));
> > +               /* SQDAO */
> > +               ufsmcq_writel(hba, MCQ_ROP_OFFSET_n(ROP_SQD, i),
> > +                             MCQ_CFG_n(REG_SQDAO, i));
>
> ...
>
> >         }
> > +
> > +out:
> > +       hba->mcq_base = res->base;
> > +       return 0;
> > +
> > +out_err:
> > +       ufshcd_mcq_release_resource(hba);
> > +       return ret;
> > +}
> > +
> > +int ufshcd_mcq_init(struct ufs_hba *hba)
> > +{
> > +       struct Scsi_Host *host = hba->host;
> > +       struct ufs_hw_queue *hwq;
> > +       int i, ret = 0;
> > +
> > +       if (!is_mcq_supported(hba))
> > +               return 0;
> > +
> > +       ret = ufshcd_mcq_config_resource(hba);
> > +       if (ret) {
> > +               dev_err(hba->dev, "Failed to config MCQ resource\n");
> > +               return ret;
> > +       }
> > +
> > +       ret = ufshcd_vops_config_mcq_rop(hba);
> > +       if (ret) {
> > +               dev_err(hba->dev, "MCQ Runtime Operation Pointers not
> > configured\n");
> > +               goto out_err;
> > +       }
> > +
> > +       hba->nr_queues[HCTX_TYPE_DEFAULT] = num_possible_cpus();
>
> 4.0 supports maximum number of queues is 32. for cpus < 32, cpu to
> queue will be 1x1, how about cpus > 32?
Good point. Will check and fix it.
> > +       hba->nr_queues[HCTX_TYPE_READ] = 0;
> > +       hba->nr_queues[HCTX_TYPE_POLL] = 1;
> > +
> > +       for (i = 0; i < HCTX_MAX_TYPES; i++)
> > +               host->nr_hw_queues += hba->nr_queues[i];
> > +
> > +       host->can_queue = hba->nutrs;
>
> Also here, can_queue is inlined with ufshci limitation, not the UFS
> device limit.
Yes, will take a look.
> > +       host->cmd_per_lun = hba->nutrs;
> > +
> > +       /* One more reserved for dev_cmd_queue */
> > +       hba->nr_hw_queues = host->nr_hw_queues + 1;
> > +
> > +       hba->uhq = devm_kmalloc(hba->dev,
> ...
> >   
> >          ufshcd_tune_unipro_params(hba);
> > @@ -9641,6 +9775,10 @@ int ufshcd_init(struct ufs_hba *hba, void
> > __iomem *mmio_base, unsigned int irq)
> >                  goto out_disable;
> >          }
> >   
> > +       err = ufshcd_mcq_init(hba);
>
> The driver will force the customer to use MCQ, how about adding a
> configuration option for the customer to choose (like eMMC CMDQ does)?
Let me check what eMMC does and see if that can be adopted here.

> Kind regards,
> Bean

-asd