[CLUE-Tech] Kernel config: Intel PIIXn ?

[Matt Gushee]

On Thu, Oct 30, 2003 at 07:01:25AM -0700, Joe 'Zonker' Brockmeier 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.
> 
> If your board has that chipset, I'd enable it. Apparently there are
> problems with PIO settings set by the motherboard if you don't have
> that. It overrides the faulty (with Linux, anyway) BIOS settings. 

Done.

On Thu, Oct 30, 2003 at 10:16:39AM -0700, Jed S. Baer wrote:
> 
> 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'.

Well, yeah. That is probably very useful if you know what PIO 0-4 mode
settings are, and/or how to use hdparm. I don't have a friggin' clue
myself. I've always found hardware* quite boring, and thus try to learn
as much as I need to know about it and no more.

[ If that makes you wonder why I am building custom kernels, the answer
  is that my motivations have been mainly related to sound drivers, 
  non-standard filesystems, and APM (or, in this case, ACPI) ]

>   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.

Interestingly, "PIIXn Tuning support" is nowhere to be found in the
2.4.22 configuration menus. Oh well.

> 
>   If unsure, say N.
> 
> 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.

Maybe it's like a Zen koan. Just meditate on it for a decade or two, and
then one day you suddenly realize you knew the answer all along ;-)

Epilogue
--------
Well, I got the kernel working. I still am not sure exactly what I did
wrong the first time, but strongly suspect it had something to do with
having accidentally compiled it with SMP support (I was sleepy!).

Anyway, thanks to Zonker and Jed for the good info.

-- 
Matt Gushee                 When a nation follows the Way,
Englewood, Colorado, USA    Horses bear manure through
mgushee at havenrock.com           its fields;
http://www.havenrock.com/   When a nation ignores the Way,
                            Horses bear soldiers through
                                its streets.
                                
                            --Lao Tzu (Peter Merel, trans.)