[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>

2 files changed, 36 insertions, 0 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index bc48d88fef5..b42acbe0e9a 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -1169,6 +1169,39 @@ ata_exec_internal(struct ata_port *ap, struct ata_device *dev,
 }
 
 /**
+ *      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
  *      @device: device bus address, starting at zero
@@ -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);
 
diff --git a/include/linux/libata.h b/include/linux/libata.h
index a43c95f8f96..af6624450f6 100644
--- a/include/linux/libata.h
+++ b/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 *,