libata: Be a bit more slack about early devices

We have a certain number of 'ATA' emulations often on CF or other flash
devices that are at best "loosely based" on the CF 1.1 standard. These
devices report themselves as disk but don't support the ATA minimal
command set only the CF 1.1 set.

Relax the PIO checking for devices reporting ATA rev 0, or no iordy
support, or CFA. Rework the code a bit as it was already messy and this
made it quite ugly.
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/libata-core.c

@@ -3132,16 +3132,21 @@ static int ata_dev_set_mode(struct ata_device *dev)
 	if (rc)
 		return rc;
 
-	/* Old CFA may refuse this command, which is just fine */
-	if (dev->xfer_shift == ATA_SHIFT_PIO && ata_id_is_cfa(dev->id))
-		ign_dev_err = 1;
-
-	/* Some very old devices and some bad newer ones fail any kind of
-	   SET_XFERMODE request but support PIO0-2 timings and no IORDY */
-	if (dev->xfer_shift == ATA_SHIFT_PIO && !ata_id_has_iordy(dev->id) &&
-			dev->pio_mode <= XFER_PIO_2)
-		ign_dev_err = 1;
-
+	if (dev->xfer_shift == ATA_SHIFT_PIO) {
+		/* Old CFA may refuse this command, which is just fine */
+		if (ata_id_is_cfa(dev->id))
+			ign_dev_err = 1;
+		/* Catch several broken garbage emulations plus some pre
+		   ATA devices */
+		if (ata_id_major_version(dev->id) == 0 &&
+					dev->pio_mode <= XFER_PIO_2)
+			ign_dev_err = 1;
+		/* Some very old devices and some bad newer ones fail
+		   any kind of SET_XFERMODE request but support PIO0-2
+		   timings and no IORDY */
+		if (!ata_id_has_iordy(dev->id) && dev->pio_mode <= XFER_PIO_2)
+			ign_dev_err = 1;
+	}
 	/* Early MWDMA devices do DMA but don't allow DMA mode setting.
 	   Don't fail an MWDMA0 set IFF the device indicates it is in MWDMA0 */
 	if (dev->xfer_shift == ATA_SHIFT_MWDMA &&