Re: [patch 2.6.14-rc1] pci: only call pci_restore_bars at boot

[Jeff Garzik <jgarzik@pobox.com>]

John W. Linville wrote:
> Certain (SGI?) ia64 boxes object to having their PCI BARs
> restored unless absolutely necessary. This patch restricts calling
> pci_restore_bars from pci_set_power_state unless the current state
> is PCI_UNKNOWN, the actual (i.e. physical) state of the device is
> PCI_D3hot, and the device indicates that it will lose its configuration
> when transitioning to PCI_D0.
> 
> Signed-off-by: John W. Linville <linville@tuxdriver.com>
> ---
> Many thanks to Keith Owens <kaos@sgi.com> for a) narrowing-down the
> problem; and, b) quickly testing the fix and reporting the results.
> 
>  drivers/pci/pci.c |   16 ++++++++++++----
>  1 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -309,17 +309,25 @@ pci_set_power_state(struct pci_dev *dev,
>  
>  	pci_read_config_word(dev, pm + PCI_PM_CTRL, &pmcsr);
>  
> -	/* If we're in D3, force entire word to 0.
> +	/* If we're (effectively) in D3, force entire word to 0.
>  	 * This doesn't affect PME_Status, disables PME_En, and
>  	 * sets PowerState to 0.
>  	 */
> -	if (dev->current_state >= PCI_D3hot) {
> -		if (!(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET))
> +	switch (dev->current_state) {
> +	case PCI_UNKNOWN: /* Boot-up */
> +		if ((pmcsr & PCI_PM_CTRL_STATE_MASK) == PCI_D3hot
> +		 && !(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET))
>  			need_restore = 1;
> +		/* Fall-through: force to D0 */
> +	case PCI_D3hot:
> +	case PCI_D3cold:
> +	case PCI_POWER_ERROR:
>  		pmcsr = 0;
> -	} else {
> +		break;
> +	default:
>  		pmcsr &= ~PCI_PM_CTRL_STATE_MASK;
>  		pmcsr |= state;
> +		break;

This seems like it will break a lot of stuff that -does- need the BARs 
restored when resuming from D3.

	Jeff