linux-kernel - Re: [PATCH v1 03/16] ufs: core: Defer adding host to scsi if mcq is supported

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Message-ID: <20221004185159.GB25671@asutoshd-linux1.qualcomm.com>
Date:   Tue, 4 Oct 2022 11:51:59 -0700
From:   Asutosh Das <quic_asutoshd@...cinc.com>
To:     Bart Van Assche <bvanassche@....org>
CC:     <mani@...nel.org>, <quic_nguyenb@...cinc.com>,
        <quic_xiaosenh@...cinc.com>, <quic_cang@...cinc.com>,
        <quic_nitirawa@...cinc.com>, <quic_rampraka@...cinc.com>,
        <quic_richardp@...cinc.com>, <stanley.chu@...iatek.com>,
        <adrian.hunter@...el.com>, <avri.altman@....com>,
        <beanhuo@...ron.com>, <martin.petersen@...cle.com>,
        <linux-scsi@...r.kernel.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v1 03/16] ufs: core: Defer adding host to scsi if mcq is
 supported

On Fri, Sep 30 2022 at 11:32 -0700, Bart Van Assche wrote:
>On 9/22/22 18:05, Asutosh Das wrote:
>>@@ -8218,6 +8219,14 @@ static int ufshcd_probe_hba(struct ufs_hba *hba, bool init_dev_params)
>>  		ret = ufshcd_device_params_init(hba);
>>  		if (ret)
>>  			goto out;
>>+
>>+		if (is_mcq_supported(hba)) {
>>+			ret = scsi_add_host(host, hba->dev);
>>+			if (ret) {
>>+				dev_err(hba->dev, "scsi_add_host failed\n");
>>+				goto out;
>>+			}
>>+		}
>>  	}
>
>Calling scsi_add_host() from ufshcd_probe_hba() seems wrong to me 
>since that function is not only called when probing a host controller 
>but also when resetting a host controller. See also 
>ufshcd_host_reset_and_restore().
>
The scsi_add_host() is only invoked from ufshcd_probe_hba() if init_dev_params
is true. That flag is false when ufshcd_probe_hba() is invoked from
ufshcd_host_reset_and_restore(). So scsi_add_host() won't be invoked from
ufshcd_host_reset_and_restore(). Even ufshcd_device_params_init() is invoked the
same way now.

>>  	ufshcd_tune_unipro_params(hba);
>>@@ -9764,10 +9773,12 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
>>  		hba->is_irq_enabled = true;
>>  	}
>>-	err = scsi_add_host(host, hba->dev);
>>-	if (err) {
>>-		dev_err(hba->dev, "scsi_add_host failed\n");
>>-		goto out_disable;
>>+	if (!is_mcq_supported(hba)) {
>>+		err = scsi_add_host(host, hba->dev);
>>+		if (err) {
>>+			dev_err(hba->dev, "scsi_add_host failed\n");
>>+			goto out_disable;
>>+		}
>>  	}
>>  	hba->tmf_tag_set = (struct blk_mq_tag_set) {
>
>Please make sure there is only a single scsi_add_host() call in the 
>UFS host controller driver.
>
One way would be to move the scsi_add_host() to ufshcd_probe_hba().
PLMK if you think this is not OK.

>Thanks,
>
>Bart.