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

["Asutosh Das (asd)" <quic_asutoshd@quicinc.com>]

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@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)?
> 
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