Re: [PATCH 14/15] ide: rework the code for selecting the best DMA transfer mode

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Hello.

Bartlomiej Zolnierkiewicz wrote:
[PATCH] ide: rework the code for selecting the best DMA transfer mode

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

  I'm now trying to rewrite hpt366.c to benefit more from these patches...
and alas, this very patch seems to be breaking filtering (at least) in this driver. :-]

Index: b/drivers/ide/ide-dma.c
===================================================================
--- 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;

  Note the subtle difference between the old and new behavior: the old driver code was applying UltraDMA filter *after*
the cable type limit, and the new code does it *before*.

+		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;
[...]
Index: b/drivers/ide/pci/hpt366.c
===================================================================
--- a/drivers/ide/pci/hpt366.c
+++ b/drivers/ide/pci/hpt366.c
@@ -513,43 +513,31 @@ static int check_in_drive_list(ide_drive
 	return 0;
 }
-static u8 hpt3xx_ratemask(ide_drive_t *drive)
-{
-	struct hpt_info *info	= pci_get_drvdata(HWIF(drive)->pci_dev);
-	u8 mode			= info->max_mode;
-
-	if (!eighty_ninty_three(drive) && mode)
-		mode = min(mode, (u8)1);
-	return mode;
-}
-
 /*
  *	Note for the future; the SATA hpt37x we must set
  *	either PIO or UDMA modes 0,4,5
  */
- -static u8 hpt3xx_ratefilter(ide_drive_t *drive, u8 speed)
+
+static u8 hpt3xx_udma_filter(ide_drive_t *drive)
 {
 	struct hpt_info *info	= pci_get_drvdata(HWIF(drive)->pci_dev);
 	u8 chip_type		= info->chip_type;
-	u8 mode			= hpt3xx_ratemask(drive);
-
-	if (drive->media != ide_disk)
-		return min(speed, (u8)XFER_PIO_4);
+	u8 mode			= info->max_mode;
+	u8 mask;
switch (mode) {
 		case 0x04:
-			speed = min_t(u8, speed, XFER_UDMA_6);
+			mask = 0x7f;
 			break;
 		case 0x03:
-			speed = min_t(u8, speed, XFER_UDMA_5);
+			mask = 0x3f;
 			if (chip_type >= HPT374)
 				break;
 			if (!check_in_drive_list(drive, bad_ata100_5))
 				goto check_bad_ata33;
 			/* fall thru */
 		case 0x02:
-			speed = min_t(u8, speed, XFER_UDMA_4);
+			mask = 0x1f;
/*
 			 * CHECK ME, Does this need to be changed to HPT374 ??
@@ -560,13 +548,13 @@ static u8 hpt3xx_ratefilter(ide_drive_t !check_in_drive_list(drive, bad_ata66_4))
 				goto check_bad_ata33;
- speed = min_t(u8, speed, XFER_UDMA_3);
+			mask = 0x0f;
 			if (HPT366_ALLOW_ATA66_3 &&
 			    !check_in_drive_list(drive, bad_ata66_3))
 				goto check_bad_ata33;
 			/* fall thru */
 		case 0x01:
-			speed = min_t(u8, speed, XFER_UDMA_2);
+			mask = 0x07;
check_bad_ata33:
 			if (chip_type >= HPT370A)

  This case 0x01 will *never* be hit for HPT370 chip with the new code, therefore the filter won't get applied.

@@ -576,10 +564,10 @@ static u8 hpt3xx_ratefilter(ide_drive_t /* fall thru */
 		case 0x00:
 		default:
-			speed = min_t(u8, speed, XFER_MW_DMA_2);
+			mask = 0x00;
 			break;
 	}
-	return speed;
+	return mask;
 }
[...]
@@ -1270,6 +1272,7 @@ static void __devinit init_hwif_hpt366(i
 	hwif->intrproc			= &hpt3xx_intrproc;
 	hwif->maskproc			= &hpt3xx_maskproc;
 	hwif->busproc			= &hpt3xx_busproc;
+	hwif->udma_filter		= &hpt3xx_udma_filter;

  In fact, we only need a filter for HPT36x/370 chips -- I'll address it in my patch.

 	/*
 	 * HPT3xxN chips have some complications:

WBR, Sergei
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