1 files changed, 74 insertions, 0 deletions

diff --git a/drivers/ide/ide-dma.c b/drivers/ide/ide-dma.c
index fd213088b06b..f28fabb791fe 100644
--- a/drivers/ide/ide-dma.c
+++ b/drivers/ide/ide-dma.c
@@ -705,6 +705,80 @@ int ide_use_dma(ide_drive_t *drive)
 
 EXPORT_SYMBOL_GPL(ide_use_dma);
 
+static const u8 xfer_mode_bases[] = {
+        XFER_UDMA_0,
+        XFER_MW_DMA_0,
+        XFER_SW_DMA_0,
+};
+
+static unsigned int ide_get_mode_mask(ide_drive_t *drive, u8 base)
+{
+        struct hd_driveid *id = drive->id;
+        ide_hwif_t *hwif = drive->hwif;
+        unsigned int mask = 0;
+
+        switch(base) {
+        case XFER_UDMA_0:
+                if ((id->field_valid & 4) == 0)
+                        break;
+
+                mask = id->dma_ultra & hwif->ultra_mask;
+
+                if (hwif->udma_filter)
+                        mask &= hwif->udma_filter(drive);
+
+                if ((mask & 0x78) && (eighty_ninty_three(drive) == 0))
+                        mask &= 0x07;
+                break;
+        case XFER_MW_DMA_0:
+                mask = id->dma_mword & hwif->mwdma_mask;
+                break;
+        case XFER_SW_DMA_0:
+                mask = id->dma_1word & hwif->swdma_mask;
+                break;
+        default:
+                BUG();
+                break;
+        }
+
+        return mask;
+}
+
+/**
+ *      ide_max_dma_mode        -       compute DMA speed
+ *      @drive: IDE device
+ *
+ *      Checks the drive capabilities and returns the speed to use
+ *      for the DMA transfer.  Returns 0 if the drive is incapable
+ *      of DMA transfers.
+ */
+
+u8 ide_max_dma_mode(ide_drive_t *drive)
+{
+        ide_hwif_t *hwif = drive->hwif;
+        unsigned int mask;
+        int x, i;
+        u8 mode = 0;
+
+        if (drive->media != ide_disk && hwif->atapi_dma == 0)
+                return 0;
+
+        for (i = 0; i < ARRAY_SIZE(xfer_mode_bases); i++) {
+                mask = ide_get_mode_mask(drive, xfer_mode_bases[i]);
+                x = fls(mask) - 1;
+                if (x >= 0) {
+                        mode = xfer_mode_bases[i] + x;
+                        break;
+                }
+        }
+
+        printk(KERN_DEBUG "%s: selected mode 0x%x\n", drive->name, mode);
+
+        return mode;
+}
+
+EXPORT_SYMBOL_GPL(ide_max_dma_mode);
+
 void ide_dma_verbose(ide_drive_t *drive)
 {
         struct hd_driveid *id   = drive->id;