Re: pci_disable_device() vs. arch

[Jeff Garzik <jgarzik@mandrakesoft.com>]

Benjamin Herrenschmidt wrote:
> 
> Hi !
> 
> Would it make sense to add a
> 
> pcibios_disable_device(pci_dev*) called from the end of
> pci_disable_device() ?
> 
> I'm adding a call to it to sungem along with other pmac stuffs
> so that the chip can be properly power down (actually it's not
> really powered down but unclocked) after module removal.
> Of course, the arch code must be able to catch it in order to
> play with the various UniNorth control bits.

What arch-specific things need to be done?

arch-specific pcibios_disable_device may be a good idea... but in this
case it sounds like you need to put #ifdef CONFIG_ALL_PPC code in
sungem.c instead, if the power-down code is specific to gmacs.


> Note that my current gmac driver does shut the chip down when
> the interface is down, which makes it a bit more useful for
> laptops as most users currently compile the driver in the kernel.

Although some drivers already do this, you really need an inactivity
timer instead of unconditionally powering-down the hardware on
dev->stop().  dhcp and other applications will often bounce the
interface...


> I have nothing about changing the policy if you prefer so that
> users will now have to rmmod the driver once done with the
> interface to save power.

For power-down specifically, you should use pci-set-power-state not
pci-disable-device.  pci_disable_device is the opposite of
pci_enable_device.  pci_enable_device not only wakes up the device, but
also assigns resources.  Which implies that pci-disable-device is
allowed to un-assign resources.  There shouldn't be a problem with a net
device doing that per se, but you should be aware of the implications.

	Jeff


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