Revert "pata_sis: Implement MWDMA for the UDMA 133 capable chips"

This reverts commit f20941f3.

Sergei Shtylyov notes "You call min() on uncomparables [in
mwdma_clip_to_pio()], i.e. mwdma_to_pio[] contains XFER_PIO_* and
adev->pio_mode - XFER_PIO_0 yields you a mode number.  Thus the second
argument will always "win" as a minimal one"

Bartlomiej Zolnierkiewicz adds "There are more issues with the patch related
to mwdma_clip_to_pio().  The function can return values between 0 and
4 which obviously won't work well for the new code below for values
>2 (i.e. resulting in out-of-bounds array access for the common-case
of dev->pio_mode == XFER_PIO_4)."

Bartlomiej Zolnierkiewicz also notes the patch is incomplete, failing to
update MWDMA mode masks.
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/pata_sis.c

@@ -252,25 +252,24 @@ static void sis_100_set_piomode (struct ata_port *ap, struct ata_device *adev)
 }
 
 /**
- *	sis_133_do_piomode - Initialize host controller PATA PIO/DMA timings
+ *	sis_133_set_piomode - Initialize host controller PATA PIO timings
  *	@ap: Port whose timings we are configuring
  *	@adev: Device we are configuring for.
  *
  *	Set PIO mode for device, in host controller PCI config space. This
- *	function handles PIO set up for the later ATA133 devices. The same
- *	timings are used for MWDMA.
+ *	function handles PIO set up for the later ATA133 devices.
  *
  *	LOCKING:
  *	None (inherited from caller).
  */
 
-static void sis_133_do_piomode(struct ata_port *ap, struct ata_device *adev,
-					int speed)
+static void sis_133_set_piomode (struct ata_port *ap, struct ata_device *adev)
 {
 	struct pci_dev *pdev	= to_pci_dev(ap->host->dev);
 	int port = 0x40;
 	u32 t1;
 	u32 reg54;
+	int speed = adev->pio_mode - XFER_PIO_0;
 
 	const u32 timing133[] = {
 		0x28269000,	/* Recovery << 24 | Act << 16 | Ini << 12 */
@@ -305,42 +304,6 @@ static void sis_133_do_piomode(struct ata_port *ap, struct ata_device *adev,
 	pci_write_config_byte(pdev, port, t1);
 }
 
-/**
- *	sis_133_set_piomode - Initialize host controller PATA PIO timings
- *	@ap: Port whose timings we are configuring
- *	@adev: Device we are configuring for.
- *
- *	Set PIO mode for device, in host controller PCI config space. This
- *	function handles PIO set up for the later ATA133 devices.
- *
- *	LOCKING:
- *	None (inherited from caller).
- */
-
-static void sis_133_set_piomode (struct ata_port *ap, struct ata_device *adev)
-{
-
-	sis_133_do_piomode(ap, adev, adev->pio_mode - XFER_PIO_0);
-}
-
-/**
- *	mwdma_clip_to_pio		-	clip MWDMA mode
- *	@adev: device
- *
- *	As the SiS shared MWDMA and PIO timings we must program the equivalent
- *	PIO timing for the MWDMA mode but we must not program one higher than
- *	the permitted PIO timing of the device.
- */
-
-static int mwdma_clip_to_pio(struct ata_device *adev)
-{
-	const int mwdma_to_pio[3] = {
-		XFER_PIO_0, XFER_PIO_3, XFER_PIO_4
-	};
-	return min(mwdma_to_pio[adev->dma_mode - XFER_MW_DMA_0],
-				adev->pio_mode - XFER_PIO_0);
-}
-
 /**
  *	sis_old_set_dmamode - Initialize host controller PATA DMA timings
  *	@ap: Port whose timings we are configuring
@@ -369,7 +332,6 @@ static void sis_old_set_dmamode (struct ata_port *ap, struct ata_device *adev)
 	if (adev->dma_mode < XFER_UDMA_0) {
 		/* bits 3-0 hold recovery timing bits 8-10 active timing and
 		   the higher bits are dependant on the device */
-		speed = mwdma_clip_to_pio(adev);
 		timing &= ~0x870F;
 		timing |= mwdma_bits[speed];
 	} else {
@@ -410,7 +372,6 @@ static void sis_66_set_dmamode (struct ata_port *ap, struct ata_device *adev)
 	if (adev->dma_mode < XFER_UDMA_0) {
 		/* bits 3-0 hold recovery timing bits 8-10 active timing and
 		   the higher bits are dependant on the device, bit 15 udma */
-		speed = mwdma_clip_to_pio(adev);
 		timing &= ~0x870F;
 		timing |= mwdma_bits[speed];
 	} else {
@@ -428,7 +389,7 @@ static void sis_66_set_dmamode (struct ata_port *ap, struct ata_device *adev)
  *	@adev: Device to program
  *
  *	Set UDMA/MWDMA mode for device, in host controller PCI config space.
- *	Handles later UDMA100 devices.
+ *	Handles UDMA66 and early UDMA100 devices.
  *
  *	LOCKING:
  *	None (inherited from caller).
@@ -439,25 +400,21 @@ static void sis_100_set_dmamode (struct ata_port *ap, struct ata_device *adev)
 	struct pci_dev *pdev	= to_pci_dev(ap->host->dev);
 	int speed = adev->dma_mode - XFER_MW_DMA_0;
 	int drive_pci = sis_old_port_base(adev);
-	u16 timing;
+	u8 timing;
 
-	const u16 udma_bits[]  = {
-		0x8B00, 0x8700, 0x8500, 0x8300, 0x8200, 0x8100};
-	const u8 mwdma_bits[] = { 0x08, 0x32, 0x31 };
+	const u8 udma_bits[]  = { 0x8B, 0x87, 0x85, 0x83, 0x82, 0x81};
 
-	pci_read_config_word(pdev, drive_pci, &timing);
+	pci_read_config_byte(pdev, drive_pci + 1, &timing);
 
 	if (adev->dma_mode < XFER_UDMA_0) {
-		speed = mwdma_clip_to_pio(adev);
-		timing &= ~0x80FF;
-		timing |= mwdma_bits[speed];
+		/* NOT SUPPORTED YET: NEED DATA SHEET. DITTO IN OLD DRIVER */
 	} else {
 		/* Bit 7 is UDMA on/off, bit 0-3 are cycle time */
 		speed = adev->dma_mode - XFER_UDMA_0;
-		timing &= ~0x8F00;
+		timing &= ~0x8F;
 		timing |= udma_bits[speed];
 	}
-	pci_write_config_word(pdev, drive_pci, timing);
+	pci_write_config_byte(pdev, drive_pci + 1, timing);
 }
 
 /**
@@ -477,26 +434,21 @@ static void sis_133_early_set_dmamode (struct ata_port *ap, struct ata_device *a
 	struct pci_dev *pdev	= to_pci_dev(ap->host->dev);
 	int speed = adev->dma_mode - XFER_MW_DMA_0;
 	int drive_pci = sis_old_port_base(adev);
-	u16 timing;
-	/* Bits 15-12  are timing */
-	static const u16 udma_bits[]  = {
-		0x8F00, 0x8A00, 0x8700, 0x8500, 0x8300, 0x8200, 0x8100
-	};
-	static const u8 mwdma_bits[] = { 0x08, 0x32, 0x31 };
+	u8 timing;
+	/* Low 4 bits are timing */
+	static const u8 udma_bits[]  = { 0x8F, 0x8A, 0x87, 0x85, 0x83, 0x82, 0x81};
 
-	pci_read_config_word(pdev, drive_pci, &timing);
+	pci_read_config_byte(pdev, drive_pci + 1, &timing);
 
 	if (adev->dma_mode < XFER_UDMA_0) {
-		speed = mwdma_clip_to_pio(adev);
-		timing &= ~0x80FF;
-		timing = mwdma_bits[speed];
+		/* NOT SUPPORTED YET: NEED DATA SHEET. DITTO IN OLD DRIVER */
 	} else {
 		/* Bit 7 is UDMA on/off, bit 0-3 are cycle time */
 		speed = adev->dma_mode - XFER_UDMA_0;
-		timing &= ~0x8F00;
+		timing &= ~0x8F;
 		timing |= udma_bits[speed];
 	}
-	pci_write_config_word(pdev, drive_pci, timing);
+	pci_write_config_byte(pdev, drive_pci + 1, timing);
 }
 
 /**
@@ -527,12 +479,13 @@ static void sis_133_set_dmamode (struct ata_port *ap, struct ata_device *adev)
 	if (reg54 & 0x40000000)
 		port = 0x70;
 	port += (8 * ap->port_no) +  (4 * adev->devno);
+
 	pci_read_config_dword(pdev, port, &t1);
 
 	if (adev->dma_mode < XFER_UDMA_0) {
-		speed = mwdma_clip_to_pio(adev);
-		sis_133_do_piomode(ap, adev, speed);
-		t1 &= ~4;	/* UDMA off */
+		t1 &= ~0x00000004;
+		/* FIXME: need data sheet to add MWDMA here. Also lacking on
+		   ide/pci driver */
 	} else {
 		speed = adev->dma_mode - XFER_UDMA_0;
 		/* if & 8 no UDMA133 - need info for ... */