libata-core: Fix simplex handling

The initial simplex handling code is fooled if you suspend and resume.
This also causes problems with some single channel controllers which
claim to be simplex.

The fix is fairly simple, instead of keeping a flag to remember if we
gave away the simplex channel we remember the actual owner. As the owner
is always part of the host_set we don't even need a refcount.

Knowing the owner also means we can reassign simplex DMA channels in
future hotplug code etc if we need to

Signed-off-by: Alan Cox <alan@redhat.com>
(and a signed-off for the patch I sent before while I remember)
Signed-off-by: Jeff Garzik <jeff@garzik.org>

2 files changed, 3 insertions, 5 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index ac3d1204ea35..eb59f167d666 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -2556,12 +2556,11 @@ int ata_set_mode(struct ata_port *ap, struct ata_device **r_failed_dev)
          * host channels are not permitted to do so.
          */
         if (used_dma && (ap->host->flags & ATA_HOST_SIMPLEX))
-                ap->host->simplex_claimed = 1;
+                ap->host->simplex_claimed = ap;
 
         /* step5: chip specific finalisation */
         if (ap->ops->post_set_mode)
                 ap->ops->post_set_mode(ap);
-
  out:
         if (rc)
                 *r_failed_dev = dev;
@@ -3444,7 +3443,7 @@ static void ata_dev_xfermask(struct ata_device *dev)
                                "device is on DMA blacklist, disabling DMA\n");
         }
 
-        if ((host->flags & ATA_HOST_SIMPLEX) && host->simplex_claimed) {
+        if ((host->flags & ATA_HOST_SIMPLEX) && host->simplex_claimed != ap) {
                 xfer_mask &= ~(ATA_MASK_MWDMA | ATA_MASK_UDMA);
                 ata_dev_printk(dev, KERN_WARNING, "simplex DMA is claimed by "
                                "other device, disabling DMA\n");
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 045fb3a72d59..3f89d13c2e9a 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -403,8 +403,7 @@ struct ata_host {
         void                    *private_data;
         const struct ata_port_operations *ops;
         unsigned long           flags;
-        int                     simplex_claimed;        /* Keep seperate in case we
-                                                           ever need to do this locked */
+        struct ata_port         *simplex_claimed;       /* channel owning the DMA */
         struct ata_port         *ports[0];
 };