[PATCH 4/4] libata: implement ATAPI per-command-type DMA horkages

[Tejun Heo <htejun@gmail.com>]

ATAPI DMA is filled with mines.  Sector aligned READ transfers usually
work but many other commands transfer non-sector aligned or variable
number of bytes, and there are devices and controllers which have
problems dealing with such non-aligned DMA transactions.

This patch implement ATAPI per-command-type DMA horkages and EH logic
to set those quickly.  This way, failures localized to certain command
type don't affect other operations (most importantly READs) and
working configuration is found quickly such that the device can be
used.

Signed-off-by: Tejun Heo <htejun@gmail.com>
---
 drivers/ata/libata-core.c |   21 +++++++++++++++++++++
 drivers/ata/libata-eh.c   |   35 +++++++++++++++++++++++++++++++++++
 include/linux/libata.h    |    4 ++++
 3 files changed, 60 insertions(+), 0 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index d763c07..32dde5b 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4628,6 +4628,27 @@ static void ata_fill_sg_dumb(struct ata_queued_cmd *qc)
 int ata_check_atapi_dma(struct ata_queued_cmd *qc)
 {
 	struct ata_port *ap = qc->ap;
+	unsigned int horkage = qc->dev->horkage;
+
+	switch (atapi_cmd_type(qc->cdb[0])) {
+	case ATAPI_READ:
+		break;
+
+	case ATAPI_WRITE:
+		if (horkage & ATAPI_DMA_HORKAGE_WRITE)
+			return 1;
+		break;
+
+	case ATAPI_READ_CD:
+		if (horkage & ATAPI_DMA_HORKAGE_READ_CD)
+			return 1;
+		break;
+
+	case ATAPI_MISC:
+		if (horkage & ATAPI_DMA_HORKAGE_MISC)
+			return 1;
+		break;
+	}
 
 	/* Don't allow DMA if it isn't multiple of 16 bytes.  Quite a
 	 * few ATAPI devices choke on such DMA requests.
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index e93dde1..4399e9e 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -1490,6 +1490,38 @@ static unsigned int ata_eh_analyze_tf(struct ata_queued_cmd *qc,
 	return action;
 }
 
+static void atapi_eh_dma_horkages(struct ata_queued_cmd *qc)
+{
+	struct ata_device *dev = qc->dev;
+	const char *type;
+
+	if (!ata_is_atapi(qc->tf.protocol) || !ata_is_dma(qc->tf.protocol) ||
+	    !(qc->err_mask & (AC_ERR_HSM | AC_ERR_TIMEOUT)))
+		return;
+
+	switch (atapi_cmd_type(qc->cdb[0])) {
+	case ATAPI_WRITE:
+		type = "WRITE";
+		dev->horkage |= ATAPI_DMA_HORKAGE_WRITE;
+		break;
+	case ATAPI_READ_CD:
+		type = "READ CD [MSF]";
+		dev->horkage |= ATAPI_DMA_HORKAGE_READ_CD;
+		break;
+	case ATAPI_MISC:
+		type = "MISC";
+		dev->horkage |= ATAPI_DMA_HORKAGE_MISC;
+		break;
+	default:
+		return;
+	}
+
+	ata_dev_printk(dev, KERN_WARNING, "ATAPI DMA for %s disabled (0x%x). \n"
+		"         If this continues to happen, please report to\n"
+		"         linux-ide@vger.kernel.org\n",
+		       type, dev->horkage);
+}
+
 static int ata_eh_categorize_error(unsigned int eflags, unsigned int err_mask,
 				   int *xfer_ok)
 {
@@ -1810,6 +1842,9 @@ static void ata_eh_link_autopsy(struct ata_link *link)
 		all_err_mask |= qc->err_mask;
 		if (qc->flags & ATA_QCFLAG_IO)
 			eflags |= ATA_EFLAG_IS_IO;
+
+		/* handle ATAPI DMA horkages */
+		atapi_eh_dma_horkages(qc);
 	}
 
 	/* enforce default EH actions */
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 9fa49e9..1601bbd 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -341,6 +341,10 @@ enum {
 	ATA_HORKAGE_IVB		= (1 << 8),	/* cbl det validity bit bugs */
 	ATA_HORKAGE_STUCK_ERR	= (1 << 9),	/* stuck ERR on next PACKET */
 
+	ATAPI_DMA_HORKAGE_WRITE		= (1 << 29), /* PIO for WRITEs */
+	ATAPI_DMA_HORKAGE_READ_CD	= (1 << 30), /* PIO for READ_CDs */
+	ATAPI_DMA_HORKAGE_MISC		= (1 << 31), /* PIO for MISC commands */
+
 	 /* DMA mask for user DMA control: User visible values; DO NOT
 	    renumber */
 	ATA_DMA_MASK_ATA	= (1 << 0),	/* DMA on ATA Disk */
-- 
1.5.2.4