[PATCH] libata: honor the transfer cycle time speficied by the EIDE device

  The following code segment is not functional because the transfer cycle time speficied by
  the EIDE device is later overwritten by ata_timing_quantize():

	/*
	 * If the drive is an EIDE drive, it can tell us it needs extended
	 * PIO/MW_DMA cycle timing.
	 */
	if (adev->id[ATA_ID_FIELD_VALID] & 2) {	/* EIDE drive */
		memset(&p, 0, sizeof(p));
		(snip)
		ata_timing_merge(&p, t, t, ATA_TIMING_CYCLE | ATA_TIMING_CYC8B);
               <== uninitialized "t" is used here
	}

	/*
	 * Convert the timing to bus clock counts.
	 */
	ata_timing_quantize(s, t, T, UT);  <== t is overwritten by quantized s

  The patch has been submitted for ide-timing.h before:
  http://marc.theaimsgroup.com/?l=linux-ide&m=110820013425454&w=2
  Resubmitted for libata.

Changes:
  - Minor fix to honor the following transfer cycle time speficied by the device
    - id[65]: Minimum Multiword DMA transfer cycle time per word
    - id[67]: Minimum PIO transfer cycle time without flow control
    - id[68]: Minimum PIO transfer cycle time with IORDY

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>
=======
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index ba1eb8b..bb604df 100644 (file)
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -1570,11 +1570,13 @@ int ata_timing_compute(struct ata_device *adev, unsigned short speed,
 
        /*
         * Find the mode. 
-       */
+        */
 
        if (!(s = ata_timing_find_mode(speed)))
                return -EINVAL;
 
+       memcpy(t, s, sizeof(*s));
+
        /*
         * If the drive is an EIDE drive, it can tell us it needs extended
         * PIO/MW_DMA cycle timing.
@@ -1595,7 +1597,7 @@ int ata_timing_compute(struct ata_device *adev, unsigned short speed,
         * Convert the timing to bus clock counts.
         */
 
-       ata_timing_quantize(s, t, T, UT);
+       ata_timing_quantize(t, t, T, UT);
 
        /*
         * Even in DMA/UDMA modes we still use PIO access for IDENTIFY, S.M.A.R.T