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>

6 files changed, 177 insertions, 2 deletions

diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
index 7e89d5c47068..892b27ced973 100644
--- a/arch/powerpc/platforms/pseries/Makefile
+++ b/arch/powerpc/platforms/pseries/Makefile
@@ -13,7 +13,7 @@ obj-$(CONFIG_KEXEC_CORE)	+= kexec.o
 obj-$(CONFIG_PSERIES_ENERGY)	+= pseries_energy.o
 
 obj-$(CONFIG_HOTPLUG_CPU)	+= hotplug-cpu.o
-obj-$(CONFIG_MEMORY_HOTPLUG)	+= hotplug-memory.o
+obj-$(CONFIG_MEMORY_HOTPLUG)	+= hotplug-memory.o pmem.o
 
 obj-$(CONFIG_HVC_CONSOLE)	+= hvconsole.o
 obj-$(CONFIG_HVCS)		+= hvcserver.o
diff --git a/arch/powerpc/platforms/pseries/dlpar.c b/arch/powerpc/platforms/pseries/dlpar.c
index 052c4f2ba0a0..7625546caefd 100644
--- a/arch/powerpc/platforms/pseries/dlpar.c
+++ b/arch/powerpc/platforms/pseries/dlpar.c
@@ -355,6 +355,10 @@ int handle_dlpar_errorlog(struct pseries_hp_errorlog *hp_elog)
 	case PSERIES_HP_ELOG_RESOURCE_CPU:
 		rc = dlpar_cpu(hp_elog);
 		break;
+	case PSERIES_HP_ELOG_RESOURCE_PMEM:
+		rc = dlpar_hp_pmem(hp_elog);
+		break;
+
 	default:
 		pr_warn_ratelimited("Invalid resource (%d) specified\n",
 				    hp_elog->resource);
diff --git a/arch/powerpc/platforms/pseries/firmware.c b/arch/powerpc/platforms/pseries/firmware.c
index 1624501386f4..608ecad0178f 100644
--- a/arch/powerpc/platforms/pseries/firmware.c
+++ b/arch/powerpc/platforms/pseries/firmware.c
@@ -66,6 +66,7 @@ hypertas_fw_features_table[] = {
 	{FW_FEATURE_BEST_ENERGY,	"hcall-best-energy-1*"},
 	{FW_FEATURE_HPT_RESIZE,		"hcall-hpt-resize"},
 	{FW_FEATURE_BLOCK_REMOVE,	"hcall-block-remove"},
+	{FW_FEATURE_PAPR_SCM,		"hcall-scm"},
 };
 
 /* Build up the firmware features bitmask using the contents of
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);
diff --git a/arch/powerpc/platforms/pseries/pseries.h b/arch/powerpc/platforms/pseries/pseries.h
index 72c0b8986536..7dee8c5d3363 100644
--- a/arch/powerpc/platforms/pseries/pseries.h
+++ b/arch/powerpc/platforms/pseries/pseries.h
@@ -65,11 +65,16 @@ int handle_dlpar_errorlog(struct pseries_hp_errorlog *hp_errlog);
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 int dlpar_memory(struct pseries_hp_errorlog *hp_elog);
+int dlpar_hp_pmem(struct pseries_hp_errorlog *hp_elog);
 #else
 static inline int dlpar_memory(struct pseries_hp_errorlog *hp_elog)
 {
 	return -EOPNOTSUPP;
 }
+static inline int dlpar_hp_pmem(struct pseries_hp_errorlog *hp_elog)
+{
+	return -EOPNOTSUPP;
+}
 #endif
 
 #ifdef CONFIG_HOTPLUG_CPU
diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index 2a9c28e4d4f9..d97d52772789 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -333,7 +333,8 @@ static irqreturn_t ras_hotplug_interrupt(int irq, void *dev_id)
 	 * hotplug events on the ras_log_buf to be handled by rtas_errd.
 	 */
 	if (hp_elog->resource == PSERIES_HP_ELOG_RESOURCE_MEM ||
-	    hp_elog->resource == PSERIES_HP_ELOG_RESOURCE_CPU)
+	    hp_elog->resource == PSERIES_HP_ELOG_RESOURCE_CPU ||
+	    hp_elog->resource == PSERIES_HP_ELOG_RESOURCE_PMEM)
 		queue_hotplug_event(hp_elog);
 	else
 		log_error(ras_log_buf, ERR_TYPE_RTAS_LOG, 0);