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 */
-