Messages in this thread | | | Date | Thu, 28 Jul 2022 14:07:19 -0700 | Subject | Re: [PATCH 1/2] scsi: ufs: Add Multi-Circular Queue support | From | "Asutosh Das (asd)" <> |
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On 7/28/2022 1:29 PM, Bart Van Assche wrote: > On 7/28/22 12:15, Asutosh Das (asd) wrote: >> Hello John, >> >> On 7/28/2022 12:10 PM, John Garry wrote: >>> On 19/07/2022 08:01, Can Guo wrote: >>>> + >>>> + hba->nr_queues[HCTX_TYPE_DEFAULT] = num_possible_cpus(); >>>> + 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; >>>> + host->cmd_per_lun = hba->nutrs; >>>> + >>>> + /* One more reserved for dev_cmd_queue */ >>>> + hba->nr_hw_queues = host->nr_hw_queues + 1; >>>> + >>> >>> So this would mean that the host can accept .can_queue * >>> .nr_hw_queues numbers of requests simultaneously - is that true? >> >> That would mean that .can_queue * .nr_hw_queues numbers of request may >> be queued to the host. >> Please can you elaborate if you see an issue. > > Hi Asutosh, > > The `host_tagset` flag has been introduced by John and Hannes some time > ago. See also commit bdb01301f3ea ("scsi: Add host and host template > flag 'host_tagset'"). This flag supports sharing tags across hardware > queues and could be used to support UFSHCI 4.0 controllers that do not > support the EXT_IID feature. > > In order not to complicate the implementation further, I propose to fall > back to the UFSHCI 3.0 compatibility mode for UFSHCI 4.0 controllers > that do not support the EXT_IID feature. > > To answer John's question: the maximum number of outstanding commands is > 16 * hba->nutrs if EXT_IID is supported (EXT_IID is a four bits field). > If the hardware queue index is encoded in the EXT_IID field, hba->nutrs > is the number of commands per hardware queue. > > Thanks, > > Bart.
Thanks Bart, I wasn't aware of the background of John's Q. I will consider your proposal and get back.
-asd
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