powerpc/eeh: EEH for pSeries hot plug

On PowerNV and pSeries, devices currently acquire EEH support from
several different places: Boot-time devices from eeh_probe_devices()
and eeh_addr_cache_build(), Virtual Function devices from the pcibios
bus add device hooks and hot plugged devices from pci_hp_add_devices()
(with other platforms using other methods as well).  Unfortunately,
pSeries machines currently discover hot plugged devices using
pci_rescan_bus(), not pci_hp_add_devices(), and so those devices do
not receive EEH support.

Rather than adding another case for pci_rescan_bus(), this change
widens the scope of the pcibios bus add device hooks so that they can
handle all devices. As a side effect this also supports devices
discovered after manually rescanning via /sys/bus/pci/rescan.

Note that on PowerNV, this change allows the EEH subsystem to become
enabled after boot as long as it has not been forced off, which was
not previously possible (it was already possible on pSeries).

Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/72ae8ae9c54097158894a52de23690448de38ea9.1565930772.git.sbobroff@linux.ibm.com

arch/powerpc/platforms/powernv/eeh-powernv.c

@@ -41,7 +41,7 @@ void pnv_pcibios_bus_add_device(struct pci_dev *pdev)
 {
 	struct pci_dn *pdn = pci_get_pdn(pdev);
 
-	if (!pdev->is_virtfn)
+	if (eeh_has_flag(EEH_FORCE_DISABLED))
 		return;
 
 	pr_debug("%s: EEH: Setting up device %s.\n", __func__, pci_name(pdev));
@@ -196,6 +196,25 @@ PNV_EEH_DBGFS_ENTRY(inbB, 0xE10);
 
 #endif /* CONFIG_DEBUG_FS */
 
+void pnv_eeh_enable_phbs(void)
+{
+	struct pci_controller *hose;
+	struct pnv_phb *phb;
+
+	list_for_each_entry(hose, &hose_list, list_node) {
+		phb = hose->private_data;
+		/*
+		 * If EEH is enabled, we're going to rely on that.
+		 * Otherwise, we restore to conventional mechanism
+		 * to clear frozen PE during PCI config access.
+		 */
+		if (eeh_enabled())
+			phb->flags |= PNV_PHB_FLAG_EEH;
+		else
+			phb->flags &= ~PNV_PHB_FLAG_EEH;
+	}
+}
+
 /**
  * pnv_eeh_post_init - EEH platform dependent post initialization
  *
@@ -234,19 +253,11 @@ int pnv_eeh_post_init(void)
 	if (!eeh_enabled())
 		disable_irq(eeh_event_irq);
 
+	pnv_eeh_enable_phbs();
+
 	list_for_each_entry(hose, &hose_list, list_node) {
 		phb = hose->private_data;
 
-		/*
-		 * If EEH is enabled, we're going to rely on that.
-		 * Otherwise, we restore to conventional mechanism
-		 * to clear frozen PE during PCI config access.
-		 */
-		if (eeh_enabled())
-			phb->flags |= PNV_PHB_FLAG_EEH;
-		else
-			phb->flags &= ~PNV_PHB_FLAG_EEH;
-
 		/* Create debugfs entries */
 #ifdef CONFIG_DEBUG_FS
 		if (phb->has_dbgfs || !phb->dbgfs)
@@ -454,7 +465,11 @@ static void *pnv_eeh_probe(struct pci_dn *pdn, void *data)
 	 * Enable EEH explicitly so that we will do EEH check
 	 * while accessing I/O stuff
 	 */
-	eeh_add_flag(EEH_ENABLED);
+	if (!eeh_has_flag(EEH_ENABLED)) {
+		enable_irq(eeh_event_irq);
+		pnv_eeh_enable_phbs();
+		eeh_add_flag(EEH_ENABLED);
+	}
 
 	/* Save memory bars */
 	eeh_save_bars(edev);