[PATCH] libata: add a function to decide if we need iordy

This ought to be simple but for PIO2 we have to poke around the drive
data to get it 100% correct.

Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

drivers/scsi/libata-core.c

@@ -1168,6 +1168,39 @@ ata_exec_internal(struct ata_port *ap, struct ata_device *dev,
 	return AC_ERR_OTHER;
 }
 
+/**
+ *	ata_pio_need_iordy	-	check if iordy needed
+ *	@adev: ATA device
+ *
+ *	Check if the current speed of the device requires IORDY. Used
+ *	by various controllers for chip configuration.
+ */
+
+unsigned int ata_pio_need_iordy(const struct ata_device *adev)
+{
+	int pio;
+	int speed = adev->pio_mode - XFER_PIO_0;
+
+	if (speed < 2)
+		return 0;
+	if (speed > 2)
+		return 1;
+
+	/* If we have no drive specific rule, then PIO 2 is non IORDY */
+
+	if (adev->id[ATA_ID_FIELD_VALID] & 2) {	/* EIDE */
+		pio = adev->id[ATA_ID_EIDE_PIO];
+		/* Is the speed faster than the drive allows non IORDY ? */
+		if (pio) {
+			/* This is cycle times not frequency - watch the logic! */
+			if (pio > 240)	/* PIO2 is 240nS per cycle */
+				return 1;
+			return 0;
+		}
+	}
+	return 0;
+}
+
 /**
  *	ata_dev_identify - obtain IDENTIFY x DEVICE page
  *	@ap: port on which device we wish to probe resides
@@ -5126,6 +5159,7 @@ EXPORT_SYMBOL_GPL(ata_dev_id_string);
 EXPORT_SYMBOL_GPL(ata_dev_config);
 EXPORT_SYMBOL_GPL(ata_scsi_simulate);
 
+EXPORT_SYMBOL_GPL(ata_pio_need_iordy);
 EXPORT_SYMBOL_GPL(ata_timing_compute);
 EXPORT_SYMBOL_GPL(ata_timing_merge);
 

include/linux/libata.h

@@ -499,6 +499,8 @@ extern int ata_scsi_slave_config(struct scsi_device *sdev);
 /*
  * Timing helpers
  */
+
+extern unsigned int ata_pio_need_iordy(const struct ata_device *);
 extern int ata_timing_compute(struct ata_device *, unsigned short,
 			      struct ata_timing *, int, int);
 extern void ata_timing_merge(const struct ata_timing *,