linux-kernel - Re: [PATCH v3 3/7] ufs: mcq: Add supporting functions for mcq abort

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Date:   Wed, 10 May 2023 14:50:16 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     "Bao D. Nguyen" <quic_nguyenb@...cinc.com>,
        quic_asutoshd@...cinc.com, quic_cang@...cinc.com, mani@...nel.org,
        stanley.chu@...iatek.com, adrian.hunter@...el.com,
        beanhuo@...ron.com, avri.altman@....com, martin.petersen@...cle.com
Cc:     linux-scsi@...r.kernel.org, Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Alice Chao <alice.chao@...iatek.com>,
        Arthur Simchaev <Arthur.Simchaev@....com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Kiwoong Kim <kwmad.kim@...sung.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/7] ufs: mcq: Add supporting functions for mcq abort

On 5/9/23 22:24, Bao D. Nguyen wrote:
> +/**
> + * ufshcd_mcq_sq_cleanup - Clean up submission queue resources
> + * associated with the pending command.
> + * @hba - per adapter instance.
> + * @task_tag - The command's task tag.
> + * @result - Result of the clean up operation.
> + *
> + * Returns 0 and result on completion. Returns error code if
> + * the operation fails.
> + */
> +int ufshcd_mcq_sq_cleanup(struct ufs_hba *hba, int task_tag, int *result)
> +{
> +	struct ufshcd_lrb *lrbp = &hba->lrb[task_tag];
> +	struct scsi_cmnd *cmd = lrbp->cmd;
> +	struct ufs_hw_queue *hwq;
> +	void __iomem *reg, *opr_sqd_base;
> +	u32 nexus, id, val;
> +	int err;
> +
> +	if (task_tag != hba->nutrs - UFSHCD_NUM_RESERVED) {
> +		if (!cmd)
> +			return FAILED;
> +		hwq = ufshcd_mcq_req_to_hwq(hba, scsi_cmd_to_rq(cmd));
> +	} else {
> +		hwq = hba->dev_cmd_queue;
> +	}
> +
> +	id = hwq->id;
> +
> +	mutex_lock(&hwq->sq_mutex);
> +
> +	/* stop the SQ fetching before working on it */
> +	err = ufshcd_mcq_sq_stop(hba, hwq);
> +	if (err)
> +		goto unlock;
> +
> +	/* SQCTI = EXT_IID, IID, LUN, Task Tag */
> +	nexus = lrbp->lun << 8 | task_tag;
> +	opr_sqd_base = mcq_opr_base(hba, OPR_SQD, id);
> +	writel(nexus, opr_sqd_base + REG_SQCTI);
> +
> +	/* SQRTCy.ICU = 1 */
> +	writel(SQ_ICU, opr_sqd_base + REG_SQRTC);
> +
> +	/* Poll SQRTSy.CUS = 1. Return result from SQRTSy.RTC */
> +	reg = opr_sqd_base + REG_SQRTS;
> +	err = read_poll_timeout(readl, val, val & SQ_CUS, 20,
> +				MCQ_POLL_US, false, reg);
> +	if (err)
> +		dev_err(hba->dev, "%s: failed. hwq=%d, lun=0x%x, tag=%d\n",
> +			__func__, id, lrbp->lun, task_tag);
> +
> +	*result = FIELD_GET(SQ_ICU_ERR_CODE_MASK, readl(reg));
> +
> +	if (ufshcd_mcq_sq_start(hba, hwq))
> +		err = FAILED;
> +
> +unlock:
> +	mutex_unlock(&hwq->sq_mutex);
> +	return err;
> +}

Please do not use the FAILED / SUCCESS return values in this function. 
These values should only be returned by functions related to SCSI error 
handling. Please do the following:
* Return a negative Unix error code in case of failure.
* Return zero upon success.
* Return the FIELD_GET() result as a positive value.
* Remove the 'int *result' argument.

> +	/* prevent concurrent access to sq hw */
> +	struct mutex sq_mutex;

Hmm ... a submission queue (SQ) exists in host memory so I'm not sure 
the "hw" part of the above comment is correct.

Thanks,

Bart.