powerpc/pseries: PAPR persistent memory support

This patch implements support for discovering storage class memory
devices at boot and for handling hotplug of new regions via RTAS
hotplug events.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
[mpe: Fix CONFIG_MEMORY_HOTPLUG=n build]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 164 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/pseries/pmem.c b/arch/powerpc/platforms/pseries/pmem.c
new file mode 100644
index 000000000000..a27f40eb57b1
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/pmem.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Handles hot and cold plug of persistent memory regions on pseries.
+ */
+
+#define pr_fmt(fmt)     "pseries-pmem: " fmt
+
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/sched.h>	/* for idle_task_exit */
+#include <linux/sched/hotplug.h>
+#include <linux/cpu.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/slab.h>
+#include <asm/prom.h>
+#include <asm/rtas.h>
+#include <asm/firmware.h>
+#include <asm/machdep.h>
+#include <asm/vdso_datapage.h>
+#include <asm/plpar_wrappers.h>
+#include <asm/topology.h>
+
+#include "pseries.h"
+#include "offline_states.h"
+
+static struct device_node *pmem_node;
+
+static ssize_t pmem_drc_add_node(u32 drc_index)
+{
+	struct device_node *dn;
+	int rc;
+
+	pr_debug("Attempting to add pmem node, drc index: %x\n", drc_index);
+
+	rc = dlpar_acquire_drc(drc_index);
+	if (rc) {
+		pr_err("Failed to acquire DRC, rc: %d, drc index: %x\n",
+			rc, drc_index);
+		return -EINVAL;
+	}
+
+	dn = dlpar_configure_connector(cpu_to_be32(drc_index), pmem_node);
+	if (!dn) {
+		pr_err("configure-connector failed for drc %x\n", drc_index);
+		dlpar_release_drc(drc_index);
+		return -EINVAL;
+	}
+
+	/* NB: The of reconfig notifier creates platform device from the node */
+	rc = dlpar_attach_node(dn, pmem_node);
+	if (rc) {
+		pr_err("Failed to attach node %s, rc: %d, drc index: %x\n",
+			dn->name, rc, drc_index);
+
+		if (dlpar_release_drc(drc_index))
+			dlpar_free_cc_nodes(dn);
+
+		return rc;
+	}
+
+	pr_info("Successfully added %pOF, drc index: %x\n", dn, drc_index);
+
+	return 0;
+}
+
+static ssize_t pmem_drc_remove_node(u32 drc_index)
+{
+	struct device_node *dn;
+	uint32_t index;
+	int rc;
+
+	for_each_child_of_node(pmem_node, dn) {
+		if (of_property_read_u32(dn, "ibm,my-drc-index", &index))
+			continue;
+		if (index == drc_index)
+			break;
+	}
+
+	if (!dn) {
+		pr_err("Attempting to remove unused DRC index %x\n", drc_index);
+		return -ENODEV;
+	}
+
+	pr_debug("Attempting to remove %pOF, drc index: %x\n", dn, drc_index);
+
+	/* * NB: tears down the ibm,pmemory device as a side-effect */
+	rc = dlpar_detach_node(dn);
+	if (rc)
+		return rc;
+
+	rc = dlpar_release_drc(drc_index);
+	if (rc) {
+		pr_err("Failed to release drc (%x) for CPU %s, rc: %d\n",
+			drc_index, dn->name, rc);
+		dlpar_attach_node(dn, pmem_node);
+		return rc;
+	}
+
+	pr_info("Successfully removed PMEM with drc index: %x\n", drc_index);
+
+	return 0;
+}
+
+int dlpar_hp_pmem(struct pseries_hp_errorlog *hp_elog)
+{
+	u32 count, drc_index;
+	int rc;
+
+	/* slim chance, but we might get a hotplug event while booting */
+	if (!pmem_node)
+		pmem_node = of_find_node_by_type(NULL, "ibm,persistent-memory");
+	if (!pmem_node) {
+		pr_err("Hotplug event for a pmem device, but none exists\n");
+		return -ENODEV;
+	}
+
+	if (hp_elog->id_type != PSERIES_HP_ELOG_ID_DRC_INDEX) {
+		pr_err("Unsupported hotplug event type %d\n",
+				hp_elog->id_type);
+		return -EINVAL;
+	}
+
+	count = hp_elog->_drc_u.drc_count;
+	drc_index = hp_elog->_drc_u.drc_index;
+
+	lock_device_hotplug();
+
+	if (hp_elog->action == PSERIES_HP_ELOG_ACTION_ADD) {
+		rc = pmem_drc_add_node(drc_index);
+	} else if (hp_elog->action == PSERIES_HP_ELOG_ACTION_REMOVE) {
+		rc = pmem_drc_remove_node(drc_index);
+	} else {
+		pr_err("Unsupported hotplug action (%d)\n", hp_elog->action);
+		rc = -EINVAL;
+	}
+
+	unlock_device_hotplug();
+	return rc;
+}
+
+const struct of_device_id drc_pmem_match[] = {
+	{ .type = "ibm,persistent-memory", },
+	{}
+};
+
+static int pseries_pmem_init(void)
+{
+	pmem_node = of_find_node_by_type(NULL, "ibm,persistent-memory");
+	if (!pmem_node)
+		return 0;
+
+	/*
+	 * The generic OF bus probe/populate handles creating platform devices
+	 * from the child (ibm,pmemory) nodes. The generic code registers an of
+	 * reconfig notifier to handle the hot-add/remove cases too.
+	 */
+	of_platform_bus_probe(pmem_node, drc_pmem_match, NULL);
+
+	return 0;
+}
+machine_arch_initcall(pseries, pseries_pmem_init);