linux-kernel - Re: [PATCH v4 5/5] scsi: ufs: ufs-mediatek: Add MCQ support for MTK platform

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Date:   Mon, 13 Mar 2023 14:36:27 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Po-Wen Kao <powen.kao@...iatek.com>, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Stanley Chu <stanley.chu@...iatek.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     wsd_upstream@...iatek.com, peter.wang@...iatek.com,
        alice.chao@...iatek.com, naomi.chu@...iatek.com,
        chun-hung.wu@...iatek.com, cc.chou@...iatek.com,
        eddie.huang@...iatek.com, mason.zhang@...iatek.com,
        chaotian.jing@...iatek.com, jiajie.hao@...iatek.com
Subject: Re: [PATCH v4 5/5] scsi: ufs: ufs-mediatek: Add MCQ support for MTK
 platform

On 3/6/23 22:54, Po-Wen Kao wrote:
> +static unsigned int mtk_mcq_irq[UFSHCD_MAX_Q_NR];

Shouldn't there be one instance of this array per controller such that 
this driver can support multiple host controllers instead of only one?

> -	err = ufshcd_make_hba_operational(hba);
> +	if (!hba->mcq_enabled) {
> +		err = ufshcd_make_hba_operational(hba);
> +	} else {
> +		ufs_mtk_config_mcq(hba, false);
> +		ufshcd_mcq_make_queues_operational(hba);
> +		ufshcd_mcq_config_mac(hba, hba->nutrs);
> +		ufshcd_writel(hba, ufshcd_readl(hba, REG_UFS_MEM_CFG) | 0x1,
> +			      REG_UFS_MEM_CFG);
> +	}

ufshcd_config_mcq() in the UFSHCD core already calls 
ufshcd_mcq_config_mac(). Why is there another call to 
ufshcd_mcq_config_mac() in the MediaTek driver?

> +	/*
> +	 * Disable MCQ_CQ_EVENT interrupt.
> +	 * Use CQ Tail Entry Push Status instead.
> +	 */
> +	ufshcd_disable_intr(hba, MCQ_CQ_EVENT_STATUS);

UFS host controller drivers should not call ufshcd_disable_intr().

 From the UFSHCI 4.0 specification: "MCQ CQ Event Status (CQES): This 
bit is transparent and becomes ‘1’ when all of the following conditions 
are met:
• Controller is operating in MCQ mode (Config.QT=1)
• ESI is not enabled (Config.ESIE=0)
• CQES set only for Events in Queues that do not have interrupt 
aggregation enabled or the Events that do not belong to MCQIACRy.IACTH 
counter operation criteria.
• At least one bit in CQISy is set and associated bit in CQIEy is set. 
y=0..31"

Is there perhaps a bug in the MediaTek controller that causes the MCQ CQ 
Event Status to be set in ESI mode? If not, can the above 
ufshcd_disable_intr() call be left out?

Thanks,

Bart.