powerpc/powernv: Setup PE for root bus

There is no parent bridge for root bus, meaning pcibios_setup_bridge()
isn't invoked for root bus. The PE for root bus is the ancestor of
other PEs in PELTV. It means we need PE for root bus populated before
all others.

This populates the PE for root bus in pcibios_setup_bridge() path
if it's not populated yet. The PE number next to the reserved one
is used as the PE# to avoid holes in continuous M64 space.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index 062f7fb..74183ff 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -194,14 +194,14 @@
 	set_bit(phb->ioda.m64_bar_idx, &phb->ioda.m64_bar_alloc);
 
 	/*
-	 * Strip off the segment used by the reserved PE, which is
-	 * expected to be 0 or last one of PE capability.
+	 * Exclude the segments for reserved and root bus PE, which
+	 * are first or last two PEs.
 	 */
 	r = &phb->hose->mem_resources[1];
 	if (phb->ioda.reserved_pe_idx == 0)
-		r->start += phb->ioda.m64_segsize;
+		r->start += (2 * phb->ioda.m64_segsize);
 	else if (phb->ioda.reserved_pe_idx == (phb->ioda.total_pe_num - 1))
-		r->end -= phb->ioda.m64_segsize;
+		r->end -= (2 * phb->ioda.m64_segsize);
 	else
 		pr_warn("  Cannot strip M64 segment for reserved PE#%d\n",
 			phb->ioda.reserved_pe_idx);
@@ -281,14 +281,14 @@
 	}
 
 	/*
-	 * Exclude the segment used by the reserved PE, which
-	 * is expected to be 0 or last supported PE#.
+	 * Exclude the segments for reserved and root bus PE, which
+	 * are first or last two PEs.
 	 */
 	r = &phb->hose->mem_resources[1];
 	if (phb->ioda.reserved_pe_idx == 0)
-		r->start += phb->ioda.m64_segsize;
+		r->start += (2 * phb->ioda.m64_segsize);
 	else if (phb->ioda.reserved_pe_idx == (phb->ioda.total_pe_num - 1))
-		r->end -= phb->ioda.m64_segsize;
+		r->end -= (2 * phb->ioda.m64_segsize);
 	else
 		WARN(1, "Wrong reserved PE#%d on PHB#%d\n",
 		     phb->ioda.reserved_pe_idx, phb->hose->global_number);
@@ -1062,8 +1062,13 @@
 		return NULL;
 	}
 
+	/* PE number for root bus should have been reserved */
+	if (pci_is_root_bus(bus) &&
+	    phb->ioda.root_pe_idx != IODA_INVALID_PE)
+		pe = &phb->ioda.pe_array[phb->ioda.root_pe_idx];
+
 	/* Check if PE is determined by M64 */
-	if (phb->pick_m64_pe)
+	if (!pe && phb->pick_m64_pe)
 		pe = phb->pick_m64_pe(bus, all);
 
 	/* The PE number isn't pinned by M64 */
@@ -3226,6 +3231,15 @@
 	struct pnv_ioda_pe *pe;
 	bool all = (pci_pcie_type(bridge) == PCI_EXP_TYPE_PCI_BRIDGE);
 
+	/* The PE for root bus should be realized before any one else */
+	if (!phb->ioda.root_pe_populated) {
+		pe = pnv_ioda_setup_bus_PE(phb->hose->bus, false);
+		if (pe) {
+			phb->ioda.root_pe_idx = pe->pe_number;
+			phb->ioda.root_pe_populated = true;
+		}
+	}
+
 	/* Don't assign PE to PCI bus, which doesn't have subordinate devices */
 	if (list_empty(&bus->devices))
 		return;
@@ -3499,7 +3513,22 @@
 			phb->ioda.dma32_segmap[segno] = IODA_INVALID_PE;
 	}
 	phb->ioda.pe_array = aux + pemap_off;
-	set_bit(phb->ioda.reserved_pe_idx, phb->ioda.pe_alloc);
+
+	/*
+	 * Choose PE number for root bus, which shouldn't have
+	 * M64 resources consumed by its child devices. To pick
+	 * the PE number adjacent to the reserved one if possible.
+	 */
+	pnv_ioda_reserve_pe(phb, phb->ioda.reserved_pe_idx);
+	if (phb->ioda.reserved_pe_idx == 0) {
+		phb->ioda.root_pe_idx = 1;
+		pnv_ioda_reserve_pe(phb, phb->ioda.root_pe_idx);
+	} else if (phb->ioda.reserved_pe_idx == (phb->ioda.total_pe_num - 1)) {
+		phb->ioda.root_pe_idx = phb->ioda.reserved_pe_idx - 1;
+		pnv_ioda_reserve_pe(phb, phb->ioda.root_pe_idx);
+	} else {
+		phb->ioda.root_pe_idx = IODA_INVALID_PE;
+	}
 
 	INIT_LIST_HEAD(&phb->ioda.pe_list);
 	mutex_init(&phb->ioda.pe_list_mutex);