[libata] Drain data on errors

If the device is signalling that there is data to drain after an error we
should read the bytes out and throw them away. Without this some devices
and controllers get wedged and don't recover.

Based on earlier work by Mark Lord

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 43 insertions, 2 deletions

diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
index f93dc029dfde..9a10cb055ac2 100644
--- a/drivers/ata/libata-sff.c
+++ b/drivers/ata/libata-sff.c
@@ -52,6 +52,7 @@ const struct ata_port_operations ata_sff_port_ops = {
 	.softreset		= ata_sff_softreset,
 	.hardreset		= sata_sff_hardreset,
 	.postreset		= ata_sff_postreset,
+	.drain_fifo		= ata_sff_drain_fifo,
 	.error_handler		= ata_sff_error_handler,
 	.post_internal_cmd	= ata_sff_post_internal_cmd,
 
@@ -2199,6 +2200,39 @@ void ata_sff_postreset(struct ata_link *link, unsigned int *classes)
 EXPORT_SYMBOL_GPL(ata_sff_postreset);
 
 /**
+ *	ata_sff_drain_fifo - Stock FIFO drain logic for SFF controllers
+ *	@qc: command
+ *
+ *	Drain the FIFO and device of any stuck data following a command
+ *	failing to complete. In some cases this is neccessary before a
+ *	reset will recover the device.
+ *
+ */
+
+void ata_sff_drain_fifo(struct ata_queued_cmd *qc)
+{
+	int count;
+	struct ata_port *ap;
+
+	/* We only need to flush incoming data when a command was running */
+	if (qc == NULL || qc->dma_dir == DMA_TO_DEVICE)
+		return;
+
+	ap = qc->ap;
+	/* Drain up to 64K of data before we give up this recovery method */
+	for (count = 0; (ap->ops->sff_check_status(ap) & ATA_DRQ)
+						&& count < 32768; count++)
+		ioread16(ap->ioaddr.data_addr);
+
+	/* Can become DEBUG later */
+	if (count)
+		ata_port_printk(ap, KERN_DEBUG,
+			"drained %d bytes to clear DRQ.\n", count);
+
+}
+EXPORT_SYMBOL_GPL(ata_sff_drain_fifo);
+
+/**
  *	ata_sff_error_handler - Stock error handler for BMDMA controller
  *	@ap: port to handle error for
  *
@@ -2239,7 +2273,8 @@ void ata_sff_error_handler(struct ata_port *ap)
 		 * really a timeout event, adjust error mask and
 		 * cancel frozen state.
 		 */
-		if (qc->err_mask == AC_ERR_TIMEOUT && (host_stat & ATA_DMA_ERR)) {
+		if (qc->err_mask == AC_ERR_TIMEOUT
+						&& (host_stat & ATA_DMA_ERR)) {
 			qc->err_mask = AC_ERR_HOST_BUS;
 			thaw = 1;
 		}
@@ -2250,6 +2285,13 @@ void ata_sff_error_handler(struct ata_port *ap)
 	ata_sff_sync(ap);		/* FIXME: We don't need this */
 	ap->ops->sff_check_status(ap);
 	ap->ops->sff_irq_clear(ap);
+	/* We *MUST* do FIFO draining before we issue a reset as several
+	 * devices helpfully clear their internal state and will lock solid
+	 * if we touch the data port post reset. Pass qc in case anyone wants
+	 *  to do different PIO/DMA recovery or has per command fixups
+	 */
+	if (ap->ops->drain_fifo)
+		ap->ops->drain_fifo(qc);
 
 	spin_unlock_irqrestore(ap->lock, flags);
 
@@ -2959,4 +3001,3 @@ out:
 EXPORT_SYMBOL_GPL(ata_pci_sff_init_one);
 
 #endif /* CONFIG_PCI */
-