[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>

drivers/ata/pata_pcmcia.c

@@ -42,7 +42,7 @@
 
 
 #define DRV_NAME "pata_pcmcia"
-#define DRV_VERSION "0.3.3"
+#define DRV_VERSION "0.3.5"
 
 /*
  *	Private data structure to glue stuff together
@@ -126,6 +126,37 @@ static unsigned int ata_data_xfer_8bit(struct ata_device *dev,
 	return buflen;
 }
 
+/**
+ *	pcmcia_8bit_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 pcmcia_8bit_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++ < 65536;)
+		ioread8(ap->ioaddr.data_addr);
+
+	if (count)
+		ata_port_printk(ap, KERN_WARNING, "drained %d bytes to clear DRQ.\n",
+								count);
+
+}
 
 static struct scsi_host_template pcmcia_sht = {
 	ATA_PIO_SHT(DRV_NAME),
@@ -143,6 +174,7 @@ static struct ata_port_operations pcmcia_8bit_port_ops = {
 	.sff_data_xfer	= ata_data_xfer_8bit,
 	.cable_detect	= ata_cable_40wire,
 	.set_mode	= pcmcia_set_mode_8bit,
+	.drain_fifo	= pcmcia_8bit_drain_fifo,
 };
 
 #define CS_CHECK(fn, ret) \