Re: proper way to assign fixed PCI resources to a "hotplug" device

[Greg KH]

On Wed, Mar 08, 2006 at 11:31:31AM +0900, Tejun Heo wrote:
> Greg KH wrote:
> >On Fri, Mar 03, 2006 at 06:18:32PM -0500, Jeff Garzik wrote:
> >
> >>I have a similar situation:
> >>
> >>BIOS initializes PCI device to mode A, I need to switch it to mode B. 
> >>To do this, I must assign a value to an MMIO PCI BAR that was not 
> >>initialized at boot.
> >>
> >>How to do this?
> >
> >
> >I really don't know, what kind of device wants to do this?
> >
> 
> Jeff is probably talking about ABAR of ICH controllers. ABAR (AHCI BAR, 
> memory mapped IO region covering all AHCI registers) isn't needed for 
> IDE mode operation and the BAR register is disabled when the chip is in 
> IDE mode. However, ABAR becomes necessary for 1. accessing SCR registers 
> (for SATA phy monitor and control) or 2. switching on AHCI mode manually 
> (some notebook BIOSes always initalize ICH6/7m's into IDE mode even when 
> the controller does support AHCI mode.
> 
> So, the problem is that the chip actually disables the PCI BAR if 
> certain switches aren't turned on and thus BIOSes are likely not to 
> reserve mmio address for the BAR. We can turn on proper switches during 
> driver initialization but we don't know how to wiggle the BAR into mmio 
> address space.

Thanks for the explaination, that makes more sense.  Unfortunatly I do
not know how to do this right now :(

Anyone with any ideas?

thanks,

greg k-h
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