[PATCH] PCI: restore BAR values after D3hot->D0 for devices that need it
Some PCI devices (e.g. 3c905B, 3c556B) lose all configuration
(including BARs) when transitioning from D3hot->D0. This leaves such
a device in an inaccessible state. The patch below causes the BARs
to be restored when enabling such a device, so that its driver will
be able to access it.
The patch also adds pci_restore_bars as a new global symbol, and adds a
correpsonding EXPORT_SYMBOL_GPL for that.
Some firmware (e.g. Thinkpad T21) leaves devices in D3hot after a
(re)boot. Most drivers call pci_enable_device very early, so devices
left in D3hot that lose configuration during the D3hot->D0 transition
will be inaccessible to their drivers.
Drivers could be modified to account for this, but it would
be difficult to know which drivers need modification. This is
especially true since often many devices are covered by the same
driver. It likely would be necessary to replicate code across dozens
of drivers.
The patch below should trigger only when transitioning from D3hot->D0
(or at boot), and only for devices that have the "no soft reset" bit
cleared in the PM control register. I believe it is safe to include
this patch as part of the PCI infrastructure.
The cleanest implementation of pci_restore_bars was to call
pci_update_resource. Unfortunately, that does not currently exist
for the sparc64 architecture. The patch below includes a null
implemenation of pci_update_resource for sparc64.
Some have expressed interest in making general use of the the
pci_restore_bars function, so that has been exported to GPL licensed
modules.
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/include/linux/pci_regs.h b/include/linux/pci_regs.h
index 7dc391c..e2a089b 100644
--- a/include/linux/pci_regs.h
+++ b/include/linux/pci_regs.h
@@ -222,6 +222,7 @@
#define PCI_PM_CAP_PME_D3cold 0x8000 /* PME# from D3 (cold) */
#define PCI_PM_CTRL 4 /* PM control and status register */
#define PCI_PM_CTRL_STATE_MASK 0x0003 /* Current power state (D0 to D3) */
+#define PCI_PM_CTRL_NO_SOFT_RESET 0x0004 /* No reset for D3hot->D0 */
#define PCI_PM_CTRL_PME_ENABLE 0x0100 /* PME pin enable */
#define PCI_PM_CTRL_DATA_SEL_MASK 0x1e00 /* Data select (??) */
#define PCI_PM_CTRL_DATA_SCALE_MASK 0x6000 /* Data scale (??) */