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

[Bean Huo <huobean@gmail.com>]

Hi Can/Asutosh

A few questions about MCQ configuration:


On Tue, 2022-07-19 at 00:01 -0700, Can Guo wrote:
> From: Asutosh Das <quic_asutoshd@quicinc.com>
> 
> Adds MCQ support to UFS driver.
> 
> Co-developed-by: Can Guo <quic_cang@quicinc.com>
> Signed-off-by: Asutosh Das <quic_asutoshd@quicinc.com>
> Signed-off-by: Can Guo <quic_cang@quicinc.com>
> ---
> 
> +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)?

> +}
> +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?

> +       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.

> +       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)?

Kind regards,
Bean