From: "Asutosh Das (asd)" <quic_asutoshd@quicinc.com>
To: Bart Van Assche <bvanassche@acm.org>,
John Garry <john.garry@huawei.com>,
Can Guo <quic_cang@quicinc.com>, <stanley.chu@mediatek.com>,
<adrian.hunter@intel.com>, <alim.akhtar@samsung.com>,
<avri.altman@wdc.com>, <beanhuo@micron.com>,
<quic_nguyenb@quicinc.com>, <quic_ziqichen@quicinc.com>,
<linux-scsi@vger.kernel.org>, <kernel-team@android.com>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Daejun Park <daejun7.park@samsung.com>,
Jinyoung Choi <j-young.choi@samsung.com>,
Kiwoong Kim <kwmad.kim@samsung.com>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] scsi: ufs: Add Multi-Circular Queue support
Date: Fri, 29 Jul 2022 09:43:21 -0700 [thread overview]
Message-ID: <59e835e6-b694-07c5-16a1-5f7774fc4177@quicinc.com> (raw)
In-Reply-To: <6da1447d-01d6-222e-fc98-7e96b154d2d0@quicinc.com>
Hi Bart,
On 7/28/2022 2:07 PM, Asutosh Das (asd) wrote:
> 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.
>
I went through the change and fwiu of your proposal is to use
host_tagset = 1 if HC doesn't support EXT_IID capability.
That way tags would be shared across 16 HWQs (4-bit IID encoding the
queue-ids).
That would also mean that the hba->nutrs would have to be adjusted such
that the tags(8-bit) don't exceed 255.
Summarily,
if EXT_IID is not supported:
host_tagset = 1, maximum configurable hba->nutrs = 16, maximum
configurable nr_hw_queues = 16.
maximum number of outstanding commands to host = 16 x 16 = 256.
if EXT_IID is supported:
host_tagset = 0, maximum confiugrable hba-nutrs = 255, maximum
configurable nr_hw_queues = 255.
Please let me know if I'm missing something.
Thank you,
-asd
next prev parent reply other threads:[~2022-07-29 16:43 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1658214120-22772-1-git-send-email-quic_cang@quicinc.com>
2022-07-19 7:01 ` [PATCH 1/2] scsi: ufs: Add Multi-Circular Queue support Can Guo
2022-07-19 23:01 ` Bart Van Assche
2022-07-19 23:07 ` Bart Van Assche
2022-07-20 17:34 ` Asutosh Das (asd)
2022-07-20 7:57 ` kernel test robot
2022-07-20 11:41 ` kernel test robot
2022-07-20 16:36 ` kernel test robot
2022-07-22 7:31 ` Avri Altman
2022-07-22 17:35 ` Asutosh Das (asd)
2022-07-22 19:37 ` Avri Altman
2022-07-22 20:14 ` Asutosh Das (asd)
2022-07-22 20:22 ` Avri Altman
2022-07-22 21:05 ` Asutosh Das (asd)
2022-07-22 17:58 ` Bart Van Assche
2022-07-26 6:48 ` Can Guo
2022-07-22 14:42 ` Avri Altman
2022-07-23 14:59 ` Avri Altman
2022-07-26 2:55 ` Can Guo
2022-07-23 15:26 ` Avri Altman
2022-07-24 3:14 ` Bart Van Assche
2022-07-25 16:24 ` Asutosh Das (asd)
2022-07-23 20:22 ` Avri Altman
2022-07-25 16:26 ` Asutosh Das (asd)
2022-07-25 19:50 ` Avri Altman
2022-07-25 20:24 ` Asutosh Das (asd)
2022-07-23 21:23 ` Avri Altman
2022-07-24 3:15 ` Bart Van Assche
2022-07-25 16:35 ` Asutosh Das (asd)
2022-07-26 22:47 ` Bart Van Assche
2022-07-24 4:07 ` Avri Altman
2022-07-25 16:38 ` Asutosh Das (asd)
2022-07-26 6:35 ` Can Guo
2022-07-26 9:46 ` Avri Altman
2022-07-24 4:32 ` Avri Altman
2022-07-26 6:21 ` Can Guo
2022-07-24 7:21 ` Avri Altman
2022-07-24 21:54 ` Bean Huo
2022-07-25 17:35 ` Asutosh Das (asd)
2022-07-25 9:16 ` Dan Carpenter
2022-07-28 19:10 ` John Garry
2022-07-28 19:15 ` Asutosh Das (asd)
2022-07-28 20:29 ` Bart Van Assche
2022-07-28 21:07 ` Asutosh Das (asd)
2022-07-29 16:43 ` Asutosh Das (asd) [this message]
2022-07-29 18:59 ` Bart Van Assche
2022-07-28 19:38 ` Bart Van Assche
2022-07-28 20:00 ` Asutosh Das (asd)
2022-07-19 7:01 ` [PATCH 2/2] scsi: ufs-qcom: Implement three CMQ related vops Can Guo
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