linux-kernel - Re: [PATCH v3 4/4] scsi: hisi_sas: Add support for DIF feature for v3 hw

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Date:   Mon, 03 Dec 2018 23:12:39 -0500
From:   "Martin K. Petersen" <martin.petersen@...cle.com>
To:     John Garry <john.garry@...wei.com>
Cc:     <jejb@...ux.vnet.ibm.com>, <martin.petersen@...cle.com>,
        <linuxarm@...wei.com>, <linux-kernel@...r.kernel.org>,
        <linux-scsi@...r.kernel.org>,
        Xiang Chen <chenxiang66@...ilicon.com>
Subject: Re: [PATCH v3 4/4] scsi: hisi_sas: Add support for DIF feature for v3 hw


John,

> +static int hisi_sas_dif_dma_map(struct hisi_hba *hisi_hba,
> +				int *n_elem_dif, struct sas_task *task)
> +{
> +	struct device *dev = hisi_hba->dev;
> +	struct sas_ssp_task *ssp_task;
> +	struct scsi_cmnd *scsi_cmnd;
> +	int rc;
> +
> +	if (task->num_scatter) {
> +		ssp_task = &task->ssp_task;
> +		scsi_cmnd = ssp_task->cmd;
> +
> +		if (scsi_prot_sg_count(scsi_cmnd)) {
> +			*n_elem_dif = dma_map_sg(dev,
> +						 scsi_prot_sglist(scsi_cmnd),
> +						 scsi_prot_sg_count(scsi_cmnd),
> +						 task->data_dir);
> +

If you're only supporting DIF there is no DMA mapping or unmapping since
the PI is generated by or verified by the HBA. No additional data is
transferred to/from host memory. The protection scatterlist will be
NULL.

> +	switch (prot_op) {
> +	case SCSI_PROT_READ_INSERT:
> +		prot->dw0 |= T10_INSRT_EN_MSK;
> +		prot->lbrtgv = lbrt_chk_val;
> +		break;
> +	case SCSI_PROT_READ_STRIP:
> +		prot->dw0 |= (T10_RMV_EN_MSK | T10_CHK_EN_MSK);
> +		prot->lbrtcv = lbrt_chk_val;
> +		if (prot_type == SCSI_PROT_DIF_TYPE1)
> +			prot->dw4 |= (0xc << 16);
> +		else if (prot_type == SCSI_PROT_DIF_TYPE3)
> +			prot->dw4 |= (0xfc << 16);
> +		break;
> +	case SCSI_PROT_READ_PASS:
> +		prot->dw0 |= T10_CHK_EN_MSK;
> +		prot->lbrtcv = lbrt_chk_val;
> +		if (prot_type == SCSI_PROT_DIF_TYPE1)
> +			prot->dw4 |= (0xc << 16);
> +		else if (prot_type == SCSI_PROT_DIF_TYPE3)
> +			prot->dw4 |= (0xfc << 16);
> +		break;
> +	case SCSI_PROT_WRITE_INSERT:
> +		prot->dw0 |= T10_INSRT_EN_MSK;
> +		prot->lbrtgv = lbrt_chk_val;
> +		break;
> +	case SCSI_PROT_WRITE_STRIP:
> +		prot->dw0 |= (T10_RMV_EN_MSK | T10_CHK_EN_MSK);
> +		prot->lbrtcv = lbrt_chk_val;
> +		break;
> +	case SCSI_PROT_WRITE_PASS:
> +		prot->dw0 |= T10_CHK_EN_MSK;
> +		prot->lbrtcv = lbrt_chk_val;
> +		if (prot_type == SCSI_PROT_DIF_TYPE1)
> +			prot->dw4 |= (0xc << 16);
> +		else if (prot_type == SCSI_PROT_DIF_TYPE3)
> +			prot->dw4 |= (0xfc << 16);
> +		break;
> +	default:
> +		WARN(1, "prot_op(0x%x) is not valid\n", prot_op);
> +		break;
> +	}

DIF is WRITE_INSERT/READ_STRIP operations only.

> +		if ((prot_op == SCSI_PROT_READ_INSERT) ||
> +		    (prot_op == SCSI_PROT_WRITE_INSERT) ||
> +		    (prot_op == SCSI_PROT_WRITE_PASS) ||
> +		    (prot_op == SCSI_PROT_READ_PASS)) {
> +			unsigned int interval = scsi_prot_interval(scsi_cmnd);
> +			unsigned int ilog2_interval = ilog2(interval);
> +
> +			len = (task->total_xfer_len >> ilog2_interval) * 8;
> +		}

if (scmd->prot_flags & SCSI_PROT_TRANSFER_PI) {

> +	.sg_prot_tablesize	= HISI_SAS_SGE_PAGE_CNT,

Also not required if you're only doing DIF. There is no protection
scatterlist.

Anyway. Instead of throwing the DIX stuff away, let's figure out what
the problem is.

-- 
Martin K. Petersen	Oracle Linux Engineering