[PATCH] ide: backport piix fixes from libata into the legacy driver

There are three flags being set by default by the PIIX driver for speeds >
PIO 1, and one not being cleared properly on fallback to PIO0.  The most
important one is the prefetch/post write control which only works for ATA
and can do bad things with ATAPI.

The patch does its best to set the flags correctly for drivers/ide.  Its
not 100% perfect but its closer than the original.  100% perfect requires
proper IORDY handling but this isn't critical (and its not right in libata
either ..  yet)

Sergei Shtylyov <sshtylyov@ru.mvista.com> said:

> +					{ 0, 0 },
> +					{ 0, 0 },
> +					{ 1, 0 },
> +					{ 2, 1 },
> +					{ 2, 3 }, };
>
>  	pio = ide_get_best_pio_mode(drive, pio, 5, NULL);

    BTW, there's quite obvious error here which leads to access outside of
timings[] if somebody passes PIO mode 5 (or autotuning code finds out that
drive supports PIO mode 5). Could have been fixed while at it... Those drives
should be rare, though...

> +		}
>  		master_data = master_data | (timings[pio][0] << 12) | (timings[pio][1] << 8);
>  	}
>  	pci_write_config_word(dev, master_port, master_data);

    Actually, there's one more serious issue with piix_tune_drive() -- it
doesn't actually set the drive's own transfer mode.

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/ide/pci/piix.c

@@ -222,13 +222,15 @@ static void piix_tune_drive (ide_drive_t *drive, u8 pio)
 	u16 master_data;
 	u8 slave_data;
 	static DEFINE_SPINLOCK(tune_lock);
+	int control = 0;
 
 				 /* ISP  RTC */
-	u8 timings[][2]	= { { 0, 0 },
-			    { 0, 0 },
-			    { 1, 0 },
-			    { 2, 1 },
-			    { 2, 3 }, };
+	static const u8 timings[][2]= {
+					{ 0, 0 },
+					{ 0, 0 },
+					{ 1, 0 },
+					{ 2, 1 },
+					{ 2, 3 }, };
 
 	pio = ide_get_best_pio_mode(drive, pio, 5, NULL);
 
@@ -239,19 +241,30 @@ static void piix_tune_drive (ide_drive_t *drive, u8 pio)
 	 */
 	spin_lock_irqsave(&tune_lock, flags);
 	pci_read_config_word(dev, master_port, &master_data);
+
+	if (pio >= 2)
+		control |= 1;	/* Programmable timing on */
+	if (drive->media == ide_disk)
+		control |= 4;	/* Prefetch, post write */
+	if (pio >= 3)
+		control |= 2;	/* IORDY */
 	if (is_slave) {
 		master_data = master_data | 0x4000;
-		if (pio > 1)
+		if (pio > 1) {
 			/* enable PPE, IE and TIME */
-			master_data = master_data | 0x0070;
+			master_data = master_data | (control << 4);
+		} else {
+			master_data &= ~0x0070;
+		}
 		pci_read_config_byte(dev, slave_port, &slave_data);
 		slave_data = slave_data & (hwif->channel ? 0x0f : 0xf0);
 		slave_data = slave_data | (((timings[pio][0] << 2) | timings[pio][1]) << (hwif->channel ? 4 : 0));
 	} else {
 		master_data = master_data & 0xccf8;
-		if (pio > 1)
+		if (pio > 1) {
 			/* enable PPE, IE and TIME */
-			master_data = master_data | 0x0007;
+			master_data = master_data | control;
+		}
 		master_data = master_data | (timings[pio][0] << 12) | (timings[pio][1] << 8);
 	}
 	pci_write_config_word(dev, master_port, master_data);