pci: Clarify power down logic

Currently pci_scan_bus() unconditionally calls pci_slot_set_power_state()
when it's finished scanning a bus. This is one of those things that
makes you go "WHAT?" when you first see it and frankly the skiboot PCI
code could do with less of that.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/core/pci.c b/core/pci.c
index 109459b..23e6775 100644
--- a/core/pci.c
+++ b/core/pci.c
@@ -401,8 +401,10 @@ static void pci_slot_set_power_state(struct phb *phb,
 
 	if (state == PCI_SLOT_POWER_OFF) {
 		/* Bail if there're something connected */
-		if (!list_empty(&pd->children))
+		if (!list_empty(&pd->children)) {
+			PCIERR(phb, pd->bdfn, "Attempted to power off slot with attached devices!\n");
 			return;
+		}
 
 		pci_slot_add_flags(slot, PCI_SLOT_FLAG_BOOTUP);
 		rc = slot->ops.get_power_state(slot, &cur_state);
@@ -915,7 +917,9 @@ uint8_t pci_scan_bus(struct phb *phb, uint8_t bus, uint8_t max_bus,
 		pci_cfg_write8(phb, pd->bdfn, PCI_CFG_SUBORDINATE_BUS, max_sub);
 		next_bus = max_sub + 1;
 
-		pci_slot_set_power_state(phb, pd, PCI_SLOT_POWER_OFF);
+		/* power off the slot if there's nothing below it */
+		if (list_empty(&pd->children))
+			pci_slot_set_power_state(phb, pd, PCI_SLOT_POWER_OFF);
 	}
 
 	return max_sub;