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sata_nv: don't use legacy DMA in ADMA mode (v2)

PATCH In review Robert Hancock 2 participants 3 messages Nov 23, 2007 – Nov 24, 2007 libata

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Robert Hancock

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#0 lore raw

PATCH 1/1 sata_nv: don't use legacy DMA in ADMA mode (v2)

We need to run any DMA command with result taskfile requested in ADMA mode when the port is in ADMA mode, otherwise it may try to use the legacy DMA engine in ADMA mode which is not allowed. Enforce this with BUG_ON() since data corruption could potentially result if this happened. Also WARN_ON() if we try and send result taskfile commands while NCQ commands are still active, since the hardware doesn't allow this.

Signed-off-by Robert Hancock <[email protected]>
drivers/ata/sata_nv.c +19 -9
@@ -791,11 +791,13 @@
 
 static void nv_adma_tf_read(struct ata_port *ap, struct ata_taskfile *tf)
 {
-	/* Since commands where a result TF is requested are not
-	   executed in ADMA mode, the only time this function will be called
-	   in ADMA mode will be if a command fails. In this case we
-	   don't care about going into register mode with ADMA commands
-	   pending, as the commands will all shortly be aborted anyway. */
+	/* Other than when internal or pass-through commands are executed,
+	   the only time this function will be called in ADMA mode will be
+	   if a command fails. In the failure case we don't care about going
+	   into register mode with ADMA commands pending, as the commands will
+	   all shortly be aborted anyway. We assume that NCQ commands are not
+	   issued via passthrough, which is the only way that switching into
+	   ADMA mode could abort outstanding commands. */
 	nv_adma_register_mode(ap);
 
 	ata_tf_read(ap, tf);

@@ -1359,11 +1361,9 @@
 	struct nv_adma_port_priv *pp = qc->ap->private_data;
 
 	/* ADMA engine can only be used for non-ATAPI DMA commands,
-	   or interrupt-driven no-data commands, where a result taskfile
-	   is not required. */
+	   or interrupt-driven no-data commands. */
 	if ((pp->flags & NV_ADMA_ATAPI_SETUP_COMPLETE) ||
-	   (qc->tf.flags & ATA_TFLAG_POLLING) ||
-	   (qc->flags & ATA_QCFLAG_RESULT_TF))
+	   (qc->tf.flags & ATA_TFLAG_POLLING))
 		return 1;
 
 	if ((qc->flags & ATA_QCFLAG_DMAMAP) ||

@@ -1381,6 +1381,8 @@
 		       NV_CPB_CTL_IEN;
 
 	if (nv_adma_use_reg_mode(qc)) {
+		BUG_ON(!(pp->flags & NV_ADMA_ATAPI_SETUP_COMPLETE) &&
+			(qc->flags & ATA_QCFLAG_DMAMAP));
 		nv_adma_register_mode(qc->ap);
 		ata_qc_prep(qc);
 		return;

@@ -1425,9 +1427,17 @@
 
 	VPRINTK("ENTER\n");
 
+	/* We can't handle result taskfile with NCQ commands active, since
+	   retrieving the taskfile switches us out of ADMA mode and would abort
+	   existing commands. */
+	WARN_ON((qc->flags & ATA_QCFLAG_RESULT_TF) &&
+		(qc->ap->qc_allocated & ~(1 << qc->tag)));
+
 	if (nv_adma_use_reg_mode(qc)) {
 		/* use ATA register mode */
 		VPRINTK("using ATA register mode: 0x%lx\n", qc->flags);
+		BUG_ON(!(pp->flags & NV_ADMA_ATAPI_SETUP_COMPLETE) &&
+			(qc->flags & ATA_QCFLAG_DMAMAP));
 		nv_adma_register_mode(qc->ap);
 		return ata_qc_issue_prot(qc);
 	} else
#1 lore raw
Quoted 10 lines · Robert Hancock

We need to run any DMA command with result taskfile requested in ADMA mode when the port is in ADMA mode, otherwise it may try to use the legacy DMA engine in ADMA mode which is not allowed. Enforce this with BUG_ON() since data corruption could potentially result if this happened. Also WARN_ON() if we try and send result taskfile commands while NCQ commands are still active, since the hardware doesn't allow this.

Signed-off-by Robert Hancock <[email protected]>

drivers/ata/sata_nv.c line 1431

Quoted 5 lines
drivers/ata/sata_nv.c +5 -0
@@ -1425,9 +1427,17 @@
+	/* We can't handle result taskfile with NCQ commands active, since
+	   retrieving the taskfile switches us out of ADMA mode and would abort
+	   existing commands. */
+	WARN_ON((qc->flags & ATA_QCFLAG_RESULT_TF) &&
+		(qc->ap->qc_allocated & ~(1 << qc->tag)));

I owe an apology here. ap->qc_allocated & ~(1 << qc->tag) test isn't correct. Sorry. qc deferring happens after qc is allocated so the condition can trigger (although it should be rare) even when nothing is going wrong, so I guess it should be WARN_ON((qc->flags & ATA_QCFLAG_RESULT_TF) && link->sactive).

Sorry. :-)

Signature · 1 line
tejun
#2 lore raw
Quoted 10 lines · Tejun Heo
Quoted 9 lines · Robert Hancock

We need to run any DMA command with result taskfile requested in ADMA mode when the port is in ADMA mode, otherwise it may try to use the legacy DMA engine in ADMA mode which is not allowed. Enforce this with BUG_ON() since data corruption could potentially result if this happened. Also WARN_ON() if we try and send result taskfile commands while NCQ commands are still active, since the hardware doesn't allow this.

Signed-off-by Robert Hancock <[email protected]>
Quoted 12 lines

drivers/ata/sata_nv.c line 1431

Quoted 6 lines
drivers/ata/sata_nv.c +5 -0
@@ -1425,9 +1427,17 @@
+	/* We can't handle result taskfile with NCQ commands active, since
+	   retrieving the taskfile switches us out of ADMA mode and would abort
+	   existing commands. */
+	WARN_ON((qc->flags & ATA_QCFLAG_RESULT_TF) &&
+		(qc->ap->qc_allocated & ~(1 << qc->tag)));

I owe an apology here. ap->qc_allocated & ~(1 << qc->tag) test isn't correct. Sorry. qc deferring happens after qc is allocated so the condition can trigger (although it should be rare) even when nothing is going wrong, so I guess it should be WARN_ON((qc->flags & ATA_QCFLAG_RESULT_TF) && link->sactive).

Or, just make the assumption clear by not allowing NCQ w/ RESULT_TF at all.

	if (unlikely(qc->tf.protocol == ATA_PROT_NCQ &&
		     (qc->flags & ATA_QCFLAG_RESULT_TF)) {
		ata_dev_printk(qc->dev, KERN_ERR,
			       "NCQ w/ RESULT_TF not allowed\n");
		return AC_ERR_SYSTEM;
	}

Thanks.

Signature · 1 line
tejun