Messages in this thread | | | Date | Thu, 28 Jul 2022 13:29:24 -0700 | Subject | Re: [PATCH 1/2] scsi: ufs: Add Multi-Circular Queue support | From | Bart Van Assche <> |
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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.
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