Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override

[Rene Herman]

On 30-12-07 21:46, Ingo Molnar wrote:
> * Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote:
>
> > > So the current plan is to go with an io_delay=udelay default in v2.6.25, 
> > > to give this a migration window, and io_delay=none in v2.6.26 [and a 
> > > complete removal of arch/x86/kernel/io_delay.c], once the _p() uses are 
> > > fixed up. This is gradual enough to notice any regressions we care about 
> > > and also makes it nicely bisectable and gradual.
> > You will break systems if you blindly go around disabling _p delays 
> > for ISA and LPC bus devices. The DEC Hinote laptops for example are 
> > well known for requiring the correct ISA and other keyboard controller 
> > delays. I don't expect anyone to test with a hinote or see it until it 
> > hits Debian or similar 'low resource' friendly devices.
>
> well, using io_delay=udelay is not 'blindly disabling'.

On the other hand, the patch you just posted that makes io_delay=none the 
default _is_ blindly disabling. So that wasn't for consumption?

io_delay=udelay additionally blindly disables the race-hiding effect the 
outb has on SMP and that Alan is seeing so many of. Should also wait for 
more driver review.

Rene.
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