[RFC] JS20 IDE perf patch

[Doug Maxey]

Anton,

  It never did get resolved in the sense that regardless of the
  tweaks, the drive seems to be limited to a throuhput number in the
  upper 20's with hdparm, even with the patches.  Suspect that I may
  be beating a dead horse.

  Why I say that is that further testing on another power platform,
  with the SII controller, shows the driver setting UDMA5 with roughly
  the same numbers from hdparm.

  Mark has asked for a definitive answer on the max drive speed from
  the manufacturer, but have yet to seen the numbers.

  In any event, if the drive is being limited by the driver, the fix
  would really need to go into 2.4, or go into 2.6 and be backported,
  if there is a discrepancy in the drive capabilities and how the
  setup is done.  But am not sure at this point if there is any
  usefulness in the patch.

++doug

On Mon, 12 Jul 2004 10:13:29 +1000, Anton Blanchard wrote:
>
>Hi Doug,
>
>Did this get sorted out or do we still need to fix it in 2.6?
>
>Anton
>
>On Mon, Dec 15, 2003 at 11:06:58AM -0600, Doug Maxey wrote:
>>
>> Howdy,
>>
>>   Have done some investigation of the AMD IDE implementation on the
>>   JS20 and have come up with a set of patches to address this.  The
>>   underlying assumption that the PCI bus can only do 66mhz is no
>>   longer true with the HT implementation on this platform.
>>
>>   The specific issues seen were:
>>   1) ide.c has code that assumes the PCI bus only runs between 20 and
>>      66 mhz.
>>   2) FW has not completely configured the chipset to run at the higher
>>      IDE bus speeds.
>>   3) amd74xx.c does not recognize and cannot use the higher PCI bus
>>      speeds to enable the higher IDE speeds.
>>
>>   Item 1 is addressed by creating ATA_PCIMHZ_MIN and ATA_PCIMHZ_MAX in
>>   linux/ide.h.  These values are used in ide/ide.c and amd74xx.c.  If
>>   there are arch specific values, they override the the values set in
>>   linux/ide.h via the arch specific header.
>>
>>   Item 2 is addressed by fixup_amd_ide in arch/ppc64/kernel/pci.c.
>>
>>   Item 3 uses the ATA_PCIMHZ* to calculate the PCI bus frequency in
>>   amd74xx.c and is used to determine the UDMA settings for the
>>   drives.
>>
>>   Please review these changes.  Comments are welcome.
>>
>> ++doug
>>
>
>


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