linux-kernel - Re: [PATCH v3 07/17] ufs: core: mcq: Calculate queue depth

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Message-ID: <0fb3f8ae-5ed7-9057-0d2b-8866f36c2441@acm.org>
Date:   Thu, 27 Oct 2022 14:52:03 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Asutosh Das <quic_asutoshd@...cinc.com>, quic_cang@...cinc.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org
Cc:     quic_nguyenb@...cinc.com, quic_xiaosenh@...cinc.com,
        stanley.chu@...iatek.com, eddie.huang@...iatek.com,
        daejun7.park@...sung.com, avri.altman@....com, mani@...nel.org,
        beanhuo@...ron.com, quic_richardp@...cinc.com,
        linux-arm-msm@...r.kernel.org,
        Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Jinyoung Choi <j-young.choi@...sung.com>,
        Kiwoong Kim <kwmad.kim@...sung.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 07/17] ufs: core: mcq: Calculate queue depth

On 10/20/22 11:03, Asutosh Das wrote:
> +u32 ufshcd_mcq_decide_queue_depth(struct ufs_hba *hba)
> +{
> +	u32 qd, val;
> +	int mac;
> +
> +	mac = ufshcd_mcq_vops_get_hba_mac(hba);
> +	if (mac < 0) {
> +		val = ufshcd_readl(hba, REG_UFS_MCQ_CFG);
> +		mac = FIELD_GET(MCQ_CFG_MAC_MASK, val);
> +	}

According to the UFSHCI 4.0 specification the MAC value is set by the 
host. Can the above code read the MAC value from the host controller 
before it has been set by the host? If so, how about leaving out the 
code that reads the MAC value from the controller and making it 
mandatory to implement the new get_hba_mac vop?

> +
> +	/*  MAC is a 0 based value. */
> +	mac += 1;
> +	/* max. value of bqueuedepth = 256, mac is host dependent */

host dependent -> defined by the host controller?

> +	qd = min_t(u32, mac, hba->dev_info.bqueuedepth);
> +	if (!qd)
> +		qd = mac;

How about using min_not_zero() instead of open-coding it?

Thanks,

Bart.