powerpc/pseries: Add driver for PAPR SCM regions

Adds a driver that implements support for enabling and accessing PAPR
SCM regions. Unfortunately due to how the PAPR interface works we can't
use the existing of_pmem driver (yet) because:

a) The guest is required to use the H_SCM_BIND_MEM h-call to add
add the SCM region to it's physical address space, and
b) There is currently no mechanism for relating a bare of_pmem region
to the backing DIMM (or not-a-DIMM for our case).

Both of these are easily handled by rolling the functionality into a
seperate driver so here we are...

Acked-by: Dan Williams <[e-mail]>
Signed-off-by: Oliver O'Halloran <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>

arch/powerpc/platforms/pseries/Kconfig

···
 	bool "Support for GX bus based adapters"
 	help
 	  Bus device driver for GX bus based adapters.
+
+config PAPR_SCM
+	depends on PPC_PSERIES && MEMORY_HOTPLUG
+	select LIBNVDIMM
+	tristate "Support for the PAPR Storage Class Memory interface"
+	help
+	  Enable access to hypervisor provided storage class memory.

arch/powerpc/platforms/pseries/Makefile

···
 obj-$(CONFIG_LPARCFG)		+= lparcfg.o
 obj-$(CONFIG_IBMVIO)		+= vio.o
 obj-$(CONFIG_IBMEBUS)		+= ibmebus.o
+obj-$(CONFIG_PAPR_SCM)		+= papr_scm.o
 
 ifdef CONFIG_PPC_PSERIES
 obj-$(CONFIG_SUSPEND)		+= suspend.o

arch/powerpc/platforms/pseries/papr_scm.c

···
+// SPDX-License-Identifier: GPL-2.0
+
+#define pr_fmt(fmt)	"papr-scm: " fmt
+
+#include <linux/of.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/ioport.h>
+#include <linux/slab.h>
+#include <linux/ndctl.h>
+#include <linux/sched.h>
+#include <linux/libnvdimm.h>
+#include <linux/platform_device.h>
+
+#include <asm/plpar_wrappers.h>
+
+#define BIND_ANY_ADDR (~0ul)
+
+#define PAPR_SCM_DIMM_CMD_MASK \
+	((1ul << ND_CMD_GET_CONFIG_SIZE) | \
+	 (1ul << ND_CMD_GET_CONFIG_DATA) | \
+	 (1ul << ND_CMD_SET_CONFIG_DATA))
+
+struct papr_scm_priv {
+	struct platform_device *pdev;
+	struct device_node *dn;
+	uint32_t drc_index;
+	uint64_t blocks;
+	uint64_t block_size;
+	int metadata_size;
+
+	uint64_t bound_addr;
+
+	struct nvdimm_bus_descriptor bus_desc;
+	struct nvdimm_bus *bus;
+	struct nvdimm *nvdimm;
+	struct resource res;
+	struct nd_region *region;
+	struct nd_interleave_set nd_set;
+};
+
+static int drc_pmem_bind(struct papr_scm_priv *p)
+{
+	unsigned long ret[PLPAR_HCALL_BUFSIZE];
+	uint64_t rc, token;
+
+	/*
+	 * When the hypervisor cannot map all the requested memory in a single
+	 * hcall it returns H_BUSY and we call again with the token until
+	 * we get H_SUCCESS. Aborting the retry loop before getting H_SUCCESS
+	 * leave the system in an undefined state, so we wait.
+	 */
+	token = 0;
+
+	do {
+		rc = plpar_hcall(H_SCM_BIND_MEM, ret, p->drc_index, 0,
+				p->blocks, BIND_ANY_ADDR, token);
+		token = be64_to_cpu(ret[0]);
+		cond_resched();
+	} while (rc == H_BUSY);
+
+	if (rc) {
+		dev_err(&p->pdev->dev, "bind err: %lld\n", rc);
+		return -ENXIO;
+	}
+
+	p->bound_addr = be64_to_cpu(ret[1]);
+
+	dev_dbg(&p->pdev->dev, "bound drc %x to %pR\n", p->drc_index, &p->res);
+
+	return 0;
+}
+
+static int drc_pmem_unbind(struct papr_scm_priv *p)
+{
+	unsigned long ret[PLPAR_HCALL_BUFSIZE];
+	uint64_t rc, token;
+
+	token = 0;
+
+	/* NB: unbind has the same retry requirements mentioned above */
+	do {
+		rc = plpar_hcall(H_SCM_UNBIND_MEM, ret, p->drc_index,
+				p->bound_addr, p->blocks, token);
+		token = be64_to_cpu(ret);
+		cond_resched();
+	} while (rc == H_BUSY);
+
+	if (rc)
+		dev_err(&p->pdev->dev, "unbind error: %lld\n", rc);
+
+	return !!rc;
+}
+
+static int papr_scm_meta_get(struct papr_scm_priv *p,
+			struct nd_cmd_get_config_data_hdr *hdr)
+{
+	unsigned long data[PLPAR_HCALL_BUFSIZE];
+	int64_t ret;
+
+	if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
+		return -EINVAL;
+
+	ret = plpar_hcall(H_SCM_READ_METADATA, data, p->drc_index,
+			hdr->in_offset, 1);
+
+	if (ret == H_PARAMETER) /* bad DRC index */
+		return -ENODEV;
+	if (ret)
+		return -EINVAL; /* other invalid parameter */
+
+	hdr->out_buf[0] = data[0] & 0xff;
+
+	return 0;
+}
+
+static int papr_scm_meta_set(struct papr_scm_priv *p,
+			struct nd_cmd_set_config_hdr *hdr)
+{
+	int64_t ret;
+
+	if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
+		return -EINVAL;
+
+	ret = plpar_hcall_norets(H_SCM_WRITE_METADATA,
+			p->drc_index, hdr->in_offset, hdr->in_buf[0], 1);
+
+	if (ret == H_PARAMETER) /* bad DRC index */
+		return -ENODEV;
+	if (ret)
+		return -EINVAL; /* other invalid parameter */
+
+	return 0;
+}
+
+int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
+		unsigned int cmd, void *buf, unsigned int buf_len, int *cmd_rc)
+{
+	struct nd_cmd_get_config_size *get_size_hdr;
+	struct papr_scm_priv *p;
+
+	/* Only dimm-specific calls are supported atm */
+	if (!nvdimm)
+		return -EINVAL;
+
+	p = nvdimm_provider_data(nvdimm);
+
+	switch (cmd) {
+	case ND_CMD_GET_CONFIG_SIZE:
+		get_size_hdr = buf;
+
+		get_size_hdr->status = 0;
+		get_size_hdr->max_xfer = 1;
+		get_size_hdr->config_size = p->metadata_size;
+		*cmd_rc = 0;
+		break;
+
+	case ND_CMD_GET_CONFIG_DATA:
+		*cmd_rc = papr_scm_meta_get(p, buf);
+		break;
+
+	case ND_CMD_SET_CONFIG_DATA:
+		*cmd_rc = papr_scm_meta_set(p, buf);
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	dev_dbg(&p->pdev->dev, "returned with cmd_rc = %d\n", *cmd_rc);
+
+	return 0;
+}
+
+static const struct attribute_group *region_attr_groups[] = {
+	&nd_region_attribute_group,
+	&nd_device_attribute_group,
+	&nd_mapping_attribute_group,
+	&nd_numa_attribute_group,
+	NULL,
+};
+
+static const struct attribute_group *bus_attr_groups[] = {
+	&nvdimm_bus_attribute_group,
+	NULL,
+};
+
+static const struct attribute_group *papr_scm_dimm_groups[] = {
+	&nvdimm_attribute_group,
+	&nd_device_attribute_group,
+	NULL,
+};
+
+static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
+{
+	struct device *dev = &p->pdev->dev;
+	struct nd_mapping_desc mapping;
+	struct nd_region_desc ndr_desc;
+	unsigned long dimm_flags;
+
+	p->bus_desc.ndctl = papr_scm_ndctl;
+	p->bus_desc.module = THIS_MODULE;
+	p->bus_desc.of_node = p->pdev->dev.of_node;
+	p->bus_desc.attr_groups = bus_attr_groups;
+	p->bus_desc.provider_name = kstrdup(p->pdev->name, GFP_KERNEL);
+
+	if (!p->bus_desc.provider_name)
+		return -ENOMEM;
+
+	p->bus = nvdimm_bus_register(NULL, &p->bus_desc);
+	if (!p->bus) {
+		dev_err(dev, "Error creating nvdimm bus %pOF\n", p->dn);
+		return -ENXIO;
+	}
+
+	dimm_flags = 0;
+	set_bit(NDD_ALIASING, &dimm_flags);
+
+	p->nvdimm = nvdimm_create(p->bus, p, papr_scm_dimm_groups,
+				dimm_flags, PAPR_SCM_DIMM_CMD_MASK, 0, NULL);
+	if (!p->nvdimm) {
+		dev_err(dev, "Error creating DIMM object for %pOF\n", p->dn);
+		goto err;
+	}
+
+	/* now add the region */
+
+	memset(&mapping, 0, sizeof(mapping));
+	mapping.nvdimm = p->nvdimm;
+	mapping.start = 0;
+	mapping.size = p->blocks * p->block_size; // XXX: potential overflow?
+
+	memset(&ndr_desc, 0, sizeof(ndr_desc));
+	ndr_desc.attr_groups = region_attr_groups;
+	ndr_desc.numa_node = dev_to_node(&p->pdev->dev);
+	ndr_desc.res = &p->res;
+	ndr_desc.of_node = p->dn;
+	ndr_desc.provider_data = p;
+	ndr_desc.mapping = &mapping;
+	ndr_desc.num_mappings = 1;
+	ndr_desc.nd_set = &p->nd_set;
+	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
+
+	p->region = nvdimm_pmem_region_create(p->bus, &ndr_desc);
+	if (!p->region) {
+		dev_err(dev, "Error registering region %pR from %pOF\n",
+				ndr_desc.res, p->dn);
+		goto err;
+	}
+
+	return 0;
+
+err:	nvdimm_bus_unregister(p->bus);
+	kfree(p->bus_desc.provider_name);
+	return -ENXIO;
+}
+
+static int papr_scm_probe(struct platform_device *pdev)
+{
+	uint32_t drc_index, metadata_size, unit_cap[2];
+	struct device_node *dn = pdev->dev.of_node;
+	struct papr_scm_priv *p;
+	int rc;
+
+	/* check we have all the required DT properties */
+	if (of_property_read_u32(dn, "ibm,my-drc-index", &drc_index)) {
+		dev_err(&pdev->dev, "%pOF: missing drc-index!\n", dn);
+		return -ENODEV;
+	}
+
+	if (of_property_read_u32_array(dn, "ibm,unit-capacity", unit_cap, 2)) {
+		dev_err(&pdev->dev, "%pOF: missing unit-capacity!\n", dn);
+		return -ENODEV;
+	}
+
+	p = kzalloc(sizeof(*p), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+
+	/* optional DT properties */
+	of_property_read_u32(dn, "ibm,metadata-size", &metadata_size);
+
+	p->dn = dn;
+	p->drc_index = drc_index;
+	p->block_size = unit_cap[0];
+	p->blocks     = unit_cap[1];
+
+	/* might be zero */
+	p->metadata_size = metadata_size;
+	p->pdev = pdev;
+
+	/* request the hypervisor to bind this region to somewhere in memory */
+	rc = drc_pmem_bind(p);
+	if (rc)
+		goto err;
+
+	/* setup the resource for the newly bound range */
+	p->res.start = p->bound_addr;
+	p->res.end   = p->bound_addr + p->blocks * p->block_size;
+	p->res.name  = pdev->name;
+	p->res.flags = IORESOURCE_MEM;
+
+	rc = papr_scm_nvdimm_init(p);
+	if (rc)
+		goto err2;
+
+	platform_set_drvdata(pdev, p);
+
+	return 0;
+
+err2:	drc_pmem_unbind(p);
+err:	kfree(p);
+	return rc;
+}
+
+static int papr_scm_remove(struct platform_device *pdev)
+{
+	struct papr_scm_priv *p = platform_get_drvdata(pdev);
+
+	nvdimm_bus_unregister(p->bus);
+	drc_pmem_unbind(p);
+	kfree(p);
+
+	return 0;
+}
+
+static const struct of_device_id papr_scm_match[] = {
+	{ .compatible = "ibm,pmemory" },
+	{ },
+};
+
+static struct platform_driver papr_scm_driver = {
+	.probe = papr_scm_probe,
+	.remove = papr_scm_remove,
+	.driver = {
+		.name = "papr_scm",
+		.owner = THIS_MODULE,
+		.of_match_table = papr_scm_match,
+	},
+};
+
+module_platform_driver(papr_scm_driver);
+MODULE_DEVICE_TABLE(of, papr_scm_match);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("IBM Corporation");