libata: fix ata_acpi_gtm_xfermask()

ata_acpi_gtm_xfermask() as separated out from pacpi_discover_modes()
has various bugs.  Fix them.

* The wrong comparison operator is used when finding for matching
  cycle resulting totally bogus result.

* With the comparion operator fixed, boundary condtion handling is
  clumsy.

* Setting of any DMA mask bit set all bits in PIO mask.

* MWDMA and UDMA blocks are swapped.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 21 insertions, 21 deletions

diff --git a/drivers/ata/libata-acpi.c b/drivers/ata/libata-acpi.c
index d6697baf243d..9f0b208afcf5 100644
--- a/drivers/ata/libata-acpi.c
+++ b/drivers/ata/libata-acpi.c
@@ -473,49 +473,49 @@ EXPORT_SYMBOL_GPL(ata_acpi_udma_cycle);
 unsigned long ata_acpi_gtm_xfermask(struct ata_device *dev,
                                     const struct ata_acpi_gtm *gtm)
 {
+        unsigned long pio_mask = 0, mwdma_mask = 0, udma_mask = 0;
         int unit, i;
         u32 t;
-        unsigned long mask = (0x7f << ATA_SHIFT_UDMA) | (0x7 << ATA_SHIFT_MWDMA) | (0x1F << ATA_SHIFT_PIO);
 
         /* we always use the 0 slot for crap hardware */
         unit = dev->devno;
         if (!(gtm->flags & 0x10))
                 unit = 0;
 
+        /* Values larger than the longest cycle results in 0 mask
+         * while values equal to smaller than the shortest cycle
+         * results in mask which includes all supported modes.
+         * Disabled transfer method has the value of 0xffffffff which
+         * will always result in 0 mask.
+         */
+
         /* start by scanning for PIO modes */
-        for (i = 0; i < 7; i++) {
-                t = gtm->drive[unit].pio;
-                if (t <= ata_acpi_pio_cycle[i]) {
-                        mask |= (2 << (ATA_SHIFT_PIO + i)) - 1;
+        t = gtm->drive[unit].pio;
+        for (i = 0; i < ARRAY_SIZE(ata_acpi_pio_cycle); i++)
+                if (t > ata_acpi_pio_cycle[i])
                         break;
-                }
-        }
+        pio_mask = (1 << i) - 1;
 
         /* See if we have MWDMA or UDMA data. We don't bother with
          * MWDMA if UDMA is available as this means the BIOS set UDMA
          * and our error changedown if it works is UDMA to PIO anyway.
          */
-        if (gtm->flags & (1 << (2 * unit))) {
+        t = gtm->drive[unit].dma;
+        if (!(gtm->flags & (1 << (2 * unit)))) {
                 /* MWDMA */
-                for (i = 0; i < 5; i++) {
-                        t = gtm->drive[unit].dma;
-                        if (t <= ata_acpi_mwdma_cycle[i]) {
-                                mask |= (2 << (ATA_SHIFT_MWDMA + i)) - 1;
+                for (i = 0; i < ARRAY_SIZE(ata_acpi_mwdma_cycle); i++)
+                        if (t > ata_acpi_mwdma_cycle[i])
                                 break;
-                        }
-                }
+                mwdma_mask = (1 << i) - 1;
         } else {
                 /* UDMA */
-                for (i = 0; i < 7; i++) {
-                        t = gtm->drive[unit].dma;
-                        if (t <= ata_acpi_udma_cycle[i]) {
-                                mask |= (2 << (ATA_SHIFT_UDMA + i)) - 1;
+                for (i = 0; i < ARRAY_SIZE(ata_acpi_udma_cycle); i++)
+                        if (t > ata_acpi_udma_cycle[i])
                                 break;
-                        }
-                }
+                udma_mask = (1 << i) - 1;
         }
 
-        return mask;
+        return ata_pack_xfermask(pio_mask, mwdma_mask, udma_mask);
 }
 EXPORT_SYMBOL_GPL(ata_acpi_gtm_xfermask);