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PCI: read current power state at enable time 

When we enable a PCI device, we avoid doing a lot of the initial setup
work if the device's enable count is non-zero.  If we don't fetch the
power state though, we may later fail to set up MSI due to the unknown
status.  So pick it up before we short circuit the rest due to a
pre-existing enable or mismatched enable/disable pair (as happens with
VGA devices, which are special in a special way).

Tested-by: Jesse Brandeburg <jesse.brandeburg@gmail.com>
Reported-by: Dave Airlie <airlied@linux.ie>
Tested-by: Dave Airlie <airlied@linux.ie>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
This commit is contained in:
Jesse Barnes 2010-11-05 15:16:36 -04:00
parent 3b519e4ea6
commit 97c145f7c8
1 changed files with 12 additions and 0 deletions
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12
drivers/pci/pci.c
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@ -1007,6 +1007,18 @@ static int __pci_enable_device_flags(struct pci_dev *dev,
int err;
int i, bars = 0;
/*
* Power state could be unknown at this point, either due to a fresh
* boot or a device removal call. So get the current power state
* so that things like MSI message writing will behave as expected
* (e.g. if the device really is in D0 at enable time).
*/
if (dev->pm_cap) {
u16 pmcsr;
pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
}
if (atomic_add_return(1, &dev->enable_cnt) > 1)
return 0; /* already enabled */