[CLUE-Tech] Kernel config: Intel PIIXn ?

[Jed S. Baer]

On Thu, 30 Oct 2003 06:32:39 -0700
Matt Gushee <matt at gushee.net> wrote:

> So anyway, my question is: how do I know whether to enable
> CONFIG_BLK_DEV_PIIX or not? The docs don't give a clear explanation of
> what it does.

You probably looked, but for the benefit of any newbie kernel builders out
there ...

There are more docs to be found in /usr/src/{kernel
version}/Documentation, and grep is your friend in finding particulars,
although often just looking at the filenames, it's clear what you'll need
to read.

In this case, from Configure.help:

Intel PIIXn chipsets support
CONFIG_BLK_DEV_PIIX
  This driver adds PIO mode setting and tuning for all PIIX IDE
  controllers by Intel.  Since the BIOS can sometimes improperly tune
  PIO 0-4 mode settings, this allows dynamic tuning of the chipset
  via the standard end-user tool 'hdparm'.

  Please read the comments at the top of <file:drivers/ide/piix.c>.

  If you say Y here, you should also say Y to "PIIXn Tuning support",
  below.

  If unsure, say N.

PIIXn Tuning support
CONFIG_PIIX_TUNING
  This driver extension adds DMA mode setting and tuning for all PIIX
  IDE controllers by Intel. Since the BIOS can sometimes improperly
  set up the device/adapter combination and speed limits, it has
  become a necessity to back/forward speed devices as needed.

  Case 430HX/440FX PIIX3 need speed limits to reduce UDMA to DMA mode
  2 if the BIOS can not perform this task at initialization.

  If unsure, say N.

Noting that it points the reader to source code comments too. I haven't
found it necessary, so far, to read the kernel sources to get make a
decision on a compile option, but when I've gone to source for other
reasons, I've found good info in the comments. YMMV.

The tangental question is how one figures out what sort of input to supply
to hdparm. I've considered tweaking my HD settings a couple of times, and
gone looking for advice on my particular drives, but never found any. So I
haven't ever done it. I occasionally see claims from people about getting
noticeable system speedups from tweaking using hdparm, and I wonder how
they determine which settings to modify.

jed
-- 
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier