Re: PCI devices with no PCI_CACHE_LINE_SIZE implemented

[Greg KH <greg@kroah.com>]

On Thu, Apr 29, 2004 at 02:53:01PM -0500, Matt Domsch wrote:
> Greg,
> 
> Some PCI device functions, such as the EHCI portion of Intel ICH5 and
> ICH6 chips, do not implement the PCI_CACHE_LINE_SIZE register (which
> is legal to not implement per PCI spec as it is a busmaster that
> cannot issue a MWI).  However, for each of these, the kernel tries to
> set the value, fails, and prints a KERN_WARNING message about it.
> 
> a) need this be a warning, wouldn't KERN_DEBUG suffice, if a message
> is needed at all?  This is printed in pci_generic_prep_mwi().

Yes, we should make that KERN_DEBUG.  I don't have a problem with that.
Care to make a patch?

> b) How might you prefer to handle such devices?
> 
> Per the PCI 2.3 spec, reading a value of 0 may mean several things:
> 1) setting the register at all isn't supported
>    - this is what pci.c assumes now and returns -EINVAL.
> 2) setting the register to the value you tried isn't supported, but
>    you can try again with another value until you find the right one.
>    - but there are no hints as to what the right value for a device
>      might be.

I think we need to stick with 1, unless we get more info on what the
"proper" value should be.

thanks,

greg k-h