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Date:   Tue, 26 Jul 2022 14:48:45 +0800
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Subject: Re: [PATCH 1/2] scsi: ufs: Add Multi-Circular Queue support
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To:     Bart Van Assche <bvanassche@acm.org>,
        Avri Altman <Avri.Altman@wdc.com>,
        "stanley.chu@mediatek.com" <stanley.chu@mediatek.com>,
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        Daejun Park <daejun7.park@samsung.com>,
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From:   Can Guo <quic_cang@quicinc.com>
In-Reply-To: <1de1372e-1c69-611b-0999-c162da8013ac@acm.org>
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Hi Bart,

On 7/23/2022 1:58 AM, Bart Van Assche wrote:
> On 7/22/22 00:31, Avri Altman wrote:
>>> +#define UFSHCD_MCQ_IO_QUEUE_OFFSET 1
>> Maybe add a comment above: "queue 0 is reserved for query commands" 
>> or something
>> That is if the query commands don't use the  legacy doorbell
>
> Is it essential to reserve a queue for device management commands? 
> Wouldn't it be better to have one additional queue for submitting I/O 
> commands rather than reserving a queue for device management commands?


Since this is just RFC change, we are trying to make the whole thing 
work with minimal efforts.

So we found that having a reserved queue (with only one active command) 
for device management

requires much less changes in ufshcd.c, because current device 
management commands anyways come

one by one (we have a mutex lock dev_cmd.lock held in 
exec_dev_command()) and it is easy to handle/assign

the task tag for device management command by just reading sq_tp_slot. 
If you think this needs to be improved,

can you please elaborate your idea? Thanks.


Regards,

Can Guo.

>
> Thanks,
>
> Bart.
>