[Skiboot] [PATCH RFC 6/6] core/pci: Hook up the writes to PRIMARY/SECONDARY/SUBORDINATE_BUS registers

[Sergey Miroshnichenko]

When Linux kernel boots with the "pci=realloc" command line argument, it
re-enumerates the PCIe topology first by dropping all the bridge's
downstream port's bus numbers to zero, and then assigns the newly
calculated bus numbers:

pci_scan_bridge_extend()
    if (pcibios_assign_all_busses())
        pci_write_config_dword(dev, PCI_PRIMARY_BUS,
                               buses & ~0xffffff);
        ...
        buses = ...
        ...
        pci_write_config_dword(dev, PCI_PRIMARY_BUS, buses);

But this leaves the corresponding struct pci_device entries in the skiboot
de-synchronized with actual values in bridge's registers.

This patch intercepts the write requests to the PCI_CFG_PRIMARY_BUS,
PCI_CFG_SECONDARY_BUS and PCI_CFG_SUBORDINATE_BUS registers, updating the
bdfn, primary_bus, secondary_bus and subordinate_bus fields.

Signed-off-by: Sergey Miroshnichenko <s.miroshnichenko at yadro.com>
---
 core/pci-opal.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 77 insertions(+), 1 deletion(-)

diff --git a/core/pci-opal.c b/core/pci-opal.c
index 009c8a6c..6b83e913 100644
--- a/core/pci-opal.c
+++ b/core/pci-opal.c
@@ -58,6 +58,80 @@ static int64_t opal_pci_config_##op(uint64_t phb_id,			\
 	return rc;							\
 }
 
+static void pci_update_children_bdfns(struct pci_device *pd)
+{
+	struct pci_device *child;
+
+	list_for_each(&pd->children, child, link) {
+		uint16_t new_bdfn = (child->bdfn & 0xff) | (pd->secondary_bus << 8);
+
+		if (child->bdfn != new_bdfn || child->primary_bus != pd->secondary_bus) {
+			if (!list_empty(&child->pcrf) && child->primary_bus)
+				bitmap_clr_bit(*child->phb->filter_map, child->bdfn);
+
+			child->bdfn = new_bdfn;
+			child->primary_bus = pd->secondary_bus;
+
+			if (!list_empty(&child->pcrf) && child->primary_bus)
+				bitmap_set_bit(*child->phb->filter_map, child->bdfn);
+
+			if (child->primary_bus && child->slot)
+				child->slot->id = PCI_SLOT_ID(child->phb, child->bdfn);
+		}
+	}
+}
+
+static void opal_pci_config_write_hook(struct phb *phb, uint16_t bdfn, uint64_t offset,
+				       uint32_t data, uint32_t size)
+{
+	struct pci_device *pd;
+	uint8_t old_sec;
+
+	if (data == 0xffffffff)
+		return;
+
+	pd = pci_find_dev_safe(phb, bdfn);
+	if (!pd) {
+		pd = pci_create_dn(phb, bdfn);
+		return;
+	}
+
+	switch (offset) {
+	case PCI_CFG_PRIMARY_BUS:
+	case PCI_CFG_SECONDARY_BUS:
+	case PCI_CFG_SUBORDINATE_BUS:
+		break;
+
+	default:
+		return;
+	}
+
+	old_sec = pd->secondary_bus;
+
+	switch (offset) {
+	case PCI_CFG_PRIMARY_BUS:
+		pd->primary_bus = data & 0xff;
+
+		if (size == 4) {
+			pd->secondary_bus = (data >> 8) & 0xff;
+			pd->subordinate_bus = (data >> 16) & 0xff;
+		}
+		break;
+
+	case PCI_CFG_SECONDARY_BUS:
+		pd->secondary_bus = data & 0xff;
+		break;
+
+	case PCI_CFG_SUBORDINATE_BUS:
+		pd->subordinate_bus = data & 0xff;
+		break;
+	}
+
+	if (pd->is_bridge && old_sec != pd->secondary_bus) {
+		pci_update_children_bdfns(pd);
+	}
+}
+
 #define OPAL_PCICFG_ACCESS_WRITE(op, cb, type)	\
 static int64_t opal_pci_config_##op(uint64_t phb_id,			\
 				    uint64_t bus_dev_func,		\
@@ -68,8 +142,10 @@ static int64_t opal_pci_config_##op(uint64_t phb_id,			\
 									\
 	if (!phb)							\
 		return OPAL_PARAMETER;					\
-	phb_lock(phb);						\
+	phb_lock(phb);							\
 	rc = phb->ops->cfg_##cb(phb, bus_dev_func, offset, data);	\
+	opal_pci_config_write_hook(phb, bus_dev_func, offset, data,	\
+				   sizeof(type));			\
 	phb_unlock(phb);						\
 									\
 	return rc;							\
-- 
2.20.1