linux-kernel - Re: [PATCH v2 1/1] ufs: core: Expand MCQ queue slot to DeviceQueueDepth + 1

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Message-ID: <cfcd744a-8986-452c-9c27-71a2e6b245f4@acm.org>
Date:   Wed, 1 Nov 2023 09:41:06 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     naomi.chu@...iatek.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     wsd_upstream@...iatek.com, peter.wang@...iatek.com,
        casper.li@...iatek.com, powen.kao@...iatek.com,
        alice.chao@...iatek.com, chun-hung.wu@...iatek.com,
        cc.chou@...iatek.com, eddie.huang@...iatek.com
Subject: Re: [PATCH v2 1/1] ufs: core: Expand MCQ queue slot to
 DeviceQueueDepth + 1

On 11/1/23 01:24, naomi.chu@...iatek.com wrote:
> From: Naomi Chu <naomi.chu@...iatek.com>
> 
> Allow UFSHCI 4.0 controllers to fully utilize MCQ queue slots.
> 
> Signed-off-by: Naomi Chu <naomi.chu@...iatek.com>
> ---
>   drivers/ufs/core/ufs-mcq.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/ufs/core/ufs-mcq.c b/drivers/ufs/core/ufs-mcq.c
> index 2ba8ec254dce..5c75ab9d6bb5 100644
> --- a/drivers/ufs/core/ufs-mcq.c
> +++ b/drivers/ufs/core/ufs-mcq.c
> @@ -436,7 +436,7 @@ int ufshcd_mcq_init(struct ufs_hba *hba)
>   
>   	for (i = 0; i < hba->nr_hw_queues; i++) {
>   		hwq = &hba->uhq[i];
> -		hwq->max_entries = hba->nutrs;
> +		hwq->max_entries = hba->nutrs + 1;
>   		spin_lock_init(&hwq->sq_lock);
>   		spin_lock_init(&hwq->cq_lock);
>   		mutex_init(&hwq->sq_mutex);

Please add a Fixes: tag and expand the patch description. What should be
mentioned in the patch description is that the UFSHCI specification
requires that there is always at least one empty slot in each completion
queue. I think that is why the above change is necessary.

Thanks,

Bart.