ide: rework the code for selecting the best DMA transfer mode (v3)

Depends on the "ide: fix UDMA/MWDMA/SWDMA masks" patch.

* add ide_hwif_t.udma_filter hook for filtering UDMA mask
  (use it in alim15x3, hpt366, siimage and serverworks drivers)
* add ide_max_dma_mode() for finding best DMA mode for the device
  (loosely based on some older libata-core.c code)
* convert ide_dma_speed() users to use ide_max_dma_mode()
* make ide_rate_filter() take "ide_drive_t *drive" as an argument instead
  of "u8 mode" and teach it to how to use UDMA mask to do filtering
* use ide_rate_filter() in hpt366 driver
* remove no longer needed ide_dma_speed() and *_ratemask()
* unexport eighty_ninty_three()

v2:
* rename ->filter_udma_mask to ->udma_filter
  [ Suggested by Sergei Shtylyov <sshtylyov@ru.mvista.com>. ]

v3:
* updated for scc_pata driver (fixes XFER_UDMA_6 filtering for user-space
  originated transfer mode change requests when 100MHz clock is used)

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

1 files changed, 18 insertions, 107 deletions

diff --git a/drivers/ide/ide-lib.c b/drivers/ide/ide-lib.c
index 68719314df3f..4557fc5a3ea3 100644
--- a/drivers/ide/ide-lib.c
+++ b/drivers/ide/ide-lib.c
@@ -69,123 +69,34 @@ char *ide_xfer_verbose (u8 xfer_rate)
 EXPORT_SYMBOL(ide_xfer_verbose);
 
 /**
- *	ide_dma_speed	-	compute DMA speed
- *	@drive: drive
- *	@mode:	modes available
- *
- *	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_dma_speed(ide_drive_t *drive, u8 mode)
-{
-	struct hd_driveid *id   = drive->id;
-	ide_hwif_t *hwif	= HWIF(drive);
-	u8 ultra_mask, mwdma_mask, swdma_mask;
-	u8 speed = 0;
-
-	if (drive->media != ide_disk && hwif->atapi_dma == 0)
-		return 0;
-
-	/* Capable of UltraDMA modes? */
-	ultra_mask = id->dma_ultra & hwif->ultra_mask;
-
-	if (!(id->field_valid & 4))
-		mode = 0;	/* fallback to MW/SW DMA if no UltraDMA */
-
-	switch (mode) {
-	case 4:
-		if (ultra_mask & 0x40) {
-			speed = XFER_UDMA_6;
-			break;
-		}
-	case 3:
-		if (ultra_mask & 0x20) {
-			speed = XFER_UDMA_5;
-			break;
-		}
-	case 2:
-		if (ultra_mask & 0x10) {
-			speed = XFER_UDMA_4;
-			break;
-		}
-		if (ultra_mask & 0x08) {
-			speed = XFER_UDMA_3;
-			break;
-		}
-	case 1:
-		if (ultra_mask & 0x04) {
-			speed = XFER_UDMA_2;
-			break;
-		}
-		if (ultra_mask & 0x02) {
-			speed = XFER_UDMA_1;
-			break;
-		}
-		if (ultra_mask & 0x01) {
-			speed = XFER_UDMA_0;
-			break;
-		}
-	case 0:
-		mwdma_mask = id->dma_mword & hwif->mwdma_mask;
-
-		if (mwdma_mask & 0x04) {
-			speed = XFER_MW_DMA_2;
-			break;
-		}
-		if (mwdma_mask & 0x02) {
-			speed = XFER_MW_DMA_1;
-			break;
-		}
-		if (mwdma_mask & 0x01) {
-			speed = XFER_MW_DMA_0;
-			break;
-		}
-
-		swdma_mask = id->dma_1word & hwif->swdma_mask;
-
-		if (swdma_mask & 0x04) {
-			speed = XFER_SW_DMA_2;
-			break;
-		}
-		if (swdma_mask & 0x02) {
-			speed = XFER_SW_DMA_1;
-			break;
-		}
-		if (swdma_mask & 0x01) {
-			speed = XFER_SW_DMA_0;
-			break;
-		}
-	}
-
-	return speed;
-}
-EXPORT_SYMBOL(ide_dma_speed);
-
-
-/**
- *	ide_rate_filter		-	return best speed for mode
- *	@mode: modes available
+ *	ide_rate_filter		-	filter transfer mode
+ *	@drive: IDE device
  *	@speed: desired speed
  *
- *	Given the available DMA/UDMA mode this function returns
+ *	Given the available transfer modes this function returns
  *	the best available speed at or below the speed requested.
+ *
+ *	FIXME: filter also PIO/SWDMA/MWDMA modes
  */
 
-u8 ide_rate_filter (u8 mode, u8 speed) 
+u8 ide_rate_filter(ide_drive_t *drive, u8 speed)
 {
 #ifdef CONFIG_BLK_DEV_IDEDMA
-	static u8 speed_max[] = {
-		XFER_MW_DMA_2, XFER_UDMA_2, XFER_UDMA_4,
-		XFER_UDMA_5, XFER_UDMA_6
-	};
+	ide_hwif_t *hwif = drive->hwif;
+	u8 mask = hwif->ultra_mask, mode = XFER_MW_DMA_2;
+
+	if (hwif->udma_filter)
+		mask = hwif->udma_filter(drive);
+
+	if ((mask & 0x78) && (eighty_ninty_three(drive) == 0))
+		mask &= 0x07;
+
+	if (mask)
+		mode = fls(mask) - 1 + XFER_UDMA_0;
 
 //	printk("%s: mode 0x%02x, speed 0x%02x\n", __FUNCTION__, mode, speed);
 
-	/* So that we remember to update this if new modes appear */
-	BUG_ON(mode > 4);
-	return min(speed, speed_max[mode]);
+	return min(speed, mode);
 #else /* !CONFIG_BLK_DEV_IDEDMA */
 	return min(speed, (u8)XFER_PIO_4);
 #endif /* CONFIG_BLK_DEV_IDEDMA */