Message-Id: <ac06c4a025d1bba50a381b187cdadbb64245cf64.camel@au1.ibm.com>
Date:   Wed, 19 Feb 2020 15:40:22 +1100
From:   "Alastair D'Silva" <alastair@....ibm.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>,
        Anton Blanchard <anton@...abs.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Cédric Le Goater <clg@...d.org>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kurz <groug@...d.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org
Subject: RE: [PATCH v2 10/27] nvdimm: Add driver for OpenCAPI Storage Class Memory

On Mon, 2020-02-03 at 13:20 +0000, Jonathan Cameron wrote:
> On Tue, 3 Dec 2019 14:46:38 +1100
> Alastair D'Silva <alastair@....ibm.com> wrote:
> 
> > From: Alastair D'Silva <alastair@...ilva.org>
> > 
> > This driver exposes LPC memory on OpenCAPI SCM cards
> > as an NVDIMM, allowing the existing nvram infrastructure
> > to be used.
> > 
> > Namespace metadata is stored on the media itself, so
> > scm_reserve_metadata() maps 1 section's worth of PMEM storage
> > at the start to hold this. The rest of the PMEM range is registered
> > with libnvdimm as an nvdimm. scm_ndctl_config_read/write/size()
> > provide
> > callbacks to libnvdimm to access the metadata.
> > 
> > Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
> Hi Alastair,
> 
> A few bits and bobs inline.
> 
> Thanks,
> 
> Jonathan
> 
> > ---
> >  drivers/nvdimm/Kconfig             |   2 +
> >  drivers/nvdimm/Makefile            |   2 +-
> >  drivers/nvdimm/ocxl/Kconfig        |  15 +
> >  drivers/nvdimm/ocxl/Makefile       |   7 +
> >  drivers/nvdimm/ocxl/scm.c          | 519
> > +++++++++++++++++++++++++++++
> >  drivers/nvdimm/ocxl/scm_internal.h |  28 ++
> >  6 files changed, 572 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/nvdimm/ocxl/Kconfig
> >  create mode 100644 drivers/nvdimm/ocxl/Makefile
> >  create mode 100644 drivers/nvdimm/ocxl/scm.c
> >  create mode 100644 drivers/nvdimm/ocxl/scm_internal.h
> > 
> > diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig
> > index 36af7af6b7cf..d1bab36da61c 100644
> > --- a/drivers/nvdimm/Kconfig
> > +++ b/drivers/nvdimm/Kconfig
> > @@ -130,4 +130,6 @@ config NVDIMM_TEST_BUILD
> >  	  core devm_memremap_pages() implementation and other
> >  	  infrastructure.
> >  
> > +source "drivers/nvdimm/ocxl/Kconfig"
> > +
> >  endif
> > diff --git a/drivers/nvdimm/Makefile b/drivers/nvdimm/Makefile
> > index 29203f3d3069..e33492128042 100644
> > --- a/drivers/nvdimm/Makefile
> > +++ b/drivers/nvdimm/Makefile
> > @@ -1,5 +1,5 @@
> >  # SPDX-License-Identifier: GPL-2.0
> > -obj-$(CONFIG_LIBNVDIMM) += libnvdimm.o
> > +obj-$(CONFIG_LIBNVDIMM) += libnvdimm.o ocxl/
> >  obj-$(CONFIG_BLK_DEV_PMEM) += nd_pmem.o
> >  obj-$(CONFIG_ND_BTT) += nd_btt.o
> >  obj-$(CONFIG_ND_BLK) += nd_blk.o
> > diff --git a/drivers/nvdimm/ocxl/Kconfig
> > b/drivers/nvdimm/ocxl/Kconfig
> > new file mode 100644
> > index 000000000000..24099b300f5e
> > --- /dev/null
> > +++ b/drivers/nvdimm/ocxl/Kconfig
> > @@ -0,0 +1,15 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +if LIBNVDIMM
> > +
> > +config OCXL_SCM
> > +	tristate "OpenCAPI Storage Class Memory"
> > +	depends on LIBNVDIMM && PPC_POWERNV && PCI && EEH
> > +	select ZONE_DEVICE
> > +	select OCXL
> > +	help
> > +	  Exposes devices that implement the OpenCAPI Storage Class
> > Memory
> > +	  specification as persistent memory regions.
> > +
> > +	  Select N if unsure.
> > +
> > +endif
> > diff --git a/drivers/nvdimm/ocxl/Makefile
> > b/drivers/nvdimm/ocxl/Makefile
> > new file mode 100644
> > index 000000000000..74a1bd98848e
> > --- /dev/null
> > +++ b/drivers/nvdimm/ocxl/Makefile
> > @@ -0,0 +1,7 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +ccflags-$(CONFIG_PPC_WERROR)	+= -Werror
> > +
> > +obj-$(CONFIG_OCXL_SCM) += ocxlscm.o
> > +
> > +ocxlscm-y := scm.o
> > diff --git a/drivers/nvdimm/ocxl/scm.c b/drivers/nvdimm/ocxl/scm.c
> > new file mode 100644
> > index 000000000000..571058a9e7b8
> > --- /dev/null
> > +++ b/drivers/nvdimm/ocxl/scm.c
> > @@ -0,0 +1,519 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +// Copyright 2019 IBM Corp.
> > +
> > +/*
> > + * A driver for Storage Class Memory, connected via OpenCAPI
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <misc/ocxl.h>
> > +#include <linux/ndctl.h>
> > +#include <linux/mm_types.h>
> > +#include <linux/memory_hotplug.h>
> > +#include "scm_internal.h"
> > +
> > +
> > +static const struct pci_device_id scm_pci_tbl[] = {
> > +	{ PCI_DEVICE(PCI_VENDOR_ID_IBM, 0x0625), },
> > +	{ }
> > +};
> > +
> > +MODULE_DEVICE_TABLE(pci, scm_pci_tbl);
> > +
> > +#define SCM_NUM_MINORS 256 // Total to reserve
> > +
> > +static dev_t scm_dev;
> > +static struct class *scm_class;
> > +static struct mutex minors_idr_lock;
> > +static struct idr minors_idr;
> > +
> > +static const struct attribute_group *scm_pmem_attribute_groups[] =
> > {
> > +	&nvdimm_bus_attribute_group,
> > +	NULL,
> > +};
> > +
> > +static const struct attribute_group
> > *scm_pmem_region_attribute_groups[] = {
> > +	&nd_region_attribute_group,
> > +	&nd_device_attribute_group,
> > +	&nd_mapping_attribute_group,
> > +	&nd_numa_attribute_group,
> > +	NULL,
> > +};
> > +
> > +/**
> > + * scm_ndctl_config_write() - Handle a ND_CMD_SET_CONFIG_DATA
> > command from ndctl
> > + * @scm_data: the SCM metadata
> > + * @command: the incoming data to write
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int scm_ndctl_config_write(struct scm_data *scm_data,
> > +				  struct nd_cmd_set_config_hdr
> > *command)
> > +{
> > +	if (command->in_offset + command->in_length >
> > SCM_LABEL_AREA_SIZE)
> > +		return -EINVAL;
> > +
> > +	memcpy_flushcache(scm_data->metadata_addr + command->in_offset, 
> > command->in_buf,
> > +			  command->in_length);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * scm_ndctl_config_read() - Handle a ND_CMD_GET_CONFIG_DATA
> > command from ndctl
> > + * @scm_data: the SCM metadata
> > + * @command: the read request
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int scm_ndctl_config_read(struct scm_data *scm_data,
> > +				 struct nd_cmd_get_config_data_hdr
> > *command)
> > +{
> > +	if (command->in_offset + command->in_length >
> > SCM_LABEL_AREA_SIZE)
> > +		return -EINVAL;
> > +
> > +	memcpy_mcsafe(command->out_buf, scm_data->metadata_addr +
> > command->in_offset,
> > +		      command->in_length);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * scm_ndctl_config_size() - Handle a ND_CMD_GET_CONFIG_SIZE
> > command from ndctl
> > + * @scm_data: the SCM metadata
> > + * @command: the read request
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int scm_ndctl_config_size(struct nd_cmd_get_config_size
> > *command)
> > +{
> > +	command->status = 0;
> > +	command->config_size = SCM_LABEL_AREA_SIZE;
> > +	command->max_xfer = PAGE_SIZE;
> > +
> > +	return 0;
> > +}
> > +
> > +static int scm_ndctl(struct nvdimm_bus_descriptor *nd_desc,
> > +		     struct nvdimm *nvdimm,
> > +		     unsigned int cmd, void *buf, unsigned int buf_len,
> > int *cmd_rc)
> > +{
> > +	struct scm_data *scm_data = container_of(nd_desc, struct
> > scm_data, bus_desc);
> > +
> > +	switch (cmd) {
> > +	case ND_CMD_GET_CONFIG_SIZE:
> > +		*cmd_rc = scm_ndctl_config_size(buf);
> > +		return 0;
> > +
> > +	case ND_CMD_GET_CONFIG_DATA:
> > +		*cmd_rc = scm_ndctl_config_read(scm_data, buf);
> > +		return 0;
> > +
> > +	case ND_CMD_SET_CONFIG_DATA:
> > +		*cmd_rc = scm_ndctl_config_write(scm_data, buf);
> > +		return 0;
> > +
> > +	default:
> > +		return -ENOTTY;
> > +	}
> > +}
> > +
> > +static ssize_t serial_show(struct device *dev,
> > +			   struct device_attribute *attr, char *buf)
> > +{
> > +	struct nvdimm *nvdimm = to_nvdimm(dev);
> > +	struct scm_data *scm_data = nvdimm_provider_data(nvdimm);
> > +	const struct ocxl_fn_config *config =
> > ocxl_function_config(scm_data->ocxl_fn);
> > +
> > +	return sprintf(buf, "0x%llx\n", config->serial);
> > +}
> > +static DEVICE_ATTR_RO(serial);
> > +
> > +static struct attribute *scm_dimm_attributes[] = {
> > +	&dev_attr_serial.attr,
> > +	NULL,
> > +};
> > +
> > +static umode_t scm_dimm_attr_visible(struct kobject *kobj,
> > +				     struct attribute *a, int n)
> > +{
> > +	return a->mode;
> > +}
> > +
> > +static const struct attribute_group scm_dimm_attribute_group = {
> > +	.name = "ocxl",
> > +	.attrs = scm_dimm_attributes,
> > +	.is_visible = scm_dimm_attr_visible,
> > +};
> > +
> > +static const struct attribute_group *scm_dimm_attribute_groups[] =
> > {
> > +	&nvdimm_attribute_group,
> > +	&nd_device_attribute_group,
> > +	&scm_dimm_attribute_group,
> > +	NULL,
> > +};
> > +
> > +/**
> > + * scm_reserve_metadata() - Reserve space for nvdimm metadata
> > + * @scm_data: The SCM device data
> > + * @lpc_mem: The resource representing the LPC memory of the SCM
> > device
> > + */
> > +static int scm_reserve_metadata(struct scm_data *scm_data,
> > +				struct resource *lpc_mem)
> > +{
> > +	scm_data->metadata_addr = devm_memremap(&scm_data->dev,
> > lpc_mem->start,
> > +						SCM_LABEL_AREA_SIZE,
> > MEMREMAP_WB);
> > +	if (IS_ERR(scm_data->metadata_addr))
> > +		return PTR_ERR(scm_data->metadata_addr);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * scm_register_lpc_mem() - Discover persistent memory on a device
> > and register it with the NVDIMM subsystem
> > + * @scm_data: The SCM device data
> > + * Return: 0 on success
> > + */
> > +static int scm_register_lpc_mem(struct scm_data *scm_data)
> > +{
> > +	struct nd_region_desc region_desc;
> > +	struct nd_mapping_desc nd_mapping_desc;
> > +	struct resource *lpc_mem;
> > +	const struct ocxl_afu_config *config;
> > +	const struct ocxl_fn_config *fn_config;
> > +	int rc;
> > +	unsigned long nvdimm_cmd_mask = 0;
> > +	unsigned long nvdimm_flags = 0;
> > +	int target_node;
> > +	char serial[16+1];
> > +
> > +	// Set up the reserved metadata area
> > +	rc = ocxl_afu_map_lpc_mem(scm_data->ocxl_afu);
> > +	if (rc < 0)
> > +		return rc;
> > +
> > +	lpc_mem = ocxl_afu_lpc_mem(scm_data->ocxl_afu);
> > +	if (lpc_mem == NULL || lpc_mem->start == 0)
> > +		return -EINVAL;
> > +
> > +	config = ocxl_afu_config(scm_data->ocxl_afu);
> > +	fn_config = ocxl_function_config(scm_data->ocxl_fn);
> > +
> > +	rc = scm_reserve_metadata(scm_data, lpc_mem);
> > +	if (rc)
> > +		return rc;
> > +
> > +	scm_data->bus_desc.attr_groups = scm_pmem_attribute_groups;
> > +	scm_data->bus_desc.provider_name = "ocxl-scm";
> > +	scm_data->bus_desc.ndctl = scm_ndctl;
> > +	scm_data->bus_desc.module = THIS_MODULE;
> > +
> > +	scm_data->nvdimm_bus = nvdimm_bus_register(&scm_data->dev,
> > +			       &scm_data->bus_desc);
> 
> odd alignment.

Ok

> 
> > +	if (!scm_data->nvdimm_bus)
> > +		return -EINVAL;
> > +
> > +	scm_data->scm_res.start = (u64)lpc_mem->start +
> > SCM_LABEL_AREA_SIZE;
> > +	scm_data->scm_res.end = (u64)lpc_mem->start + config-
> > >lpc_mem_size - 1;
> > +	scm_data->scm_res.name = "SCM persistent memory";
> > +
> > +	set_bit(ND_CMD_GET_CONFIG_SIZE, &nvdimm_cmd_mask);
> > +	set_bit(ND_CMD_GET_CONFIG_DATA, &nvdimm_cmd_mask);
> > +	set_bit(ND_CMD_SET_CONFIG_DATA, &nvdimm_cmd_mask);
> > +
> > +	set_bit(NDD_ALIASING, &nvdimm_flags);
> > +
> > +	snprintf(serial, sizeof(serial), "%llx", fn_config->serial);
> > +	nd_mapping_desc.nvdimm = nvdimm_create(scm_data->nvdimm_bus,
> > scm_data,
> > +				 scm_dimm_attribute_groups,
> > +				 nvdimm_flags, nvdimm_cmd_mask,
> > +				 0, NULL);
> > +	if (!nd_mapping_desc.nvdimm)
> > +		return -ENOMEM;
> > +
> > +	if (nvdimm_bus_check_dimm_count(scm_data->nvdimm_bus, 1))
> > +		return -EINVAL;
> > +
> > +	nd_mapping_desc.start = scm_data->scm_res.start;
> > +	nd_mapping_desc.size = resource_size(&scm_data->scm_res);
> > +	nd_mapping_desc.position = 0;
> > +
> > +	scm_data->nd_set.cookie1 = fn_config->serial + 1; // allow for
> > empty serial
> > +	scm_data->nd_set.cookie2 = fn_config->serial + 1;
> > +
> > +	target_node = of_node_to_nid(scm_data->pdev->dev.of_node);
> > +
> > +	memset(&region_desc, 0, sizeof(region_desc));
> > +	region_desc.res = &scm_data->scm_res;
> > +	region_desc.attr_groups = scm_pmem_region_attribute_groups;
> > +	region_desc.numa_node = NUMA_NO_NODE;
> > +	region_desc.target_node = target_node;
> > +	region_desc.num_mappings = 1;
> > +	region_desc.mapping = &nd_mapping_desc;
> > +	region_desc.nd_set = &scm_data->nd_set;
> > +
> > +	set_bit(ND_REGION_PAGEMAP, &region_desc.flags);
> > +	/*
> > +	 * NB: libnvdimm copies the data from ndr_desc into it's own
> > +	 * structures so passing a stack pointer is fine.
> > +	 */
> > +	scm_data->nd_region = nvdimm_pmem_region_create(scm_data-
> > >nvdimm_bus,
> > +			      &region_desc);
> > +	if (!scm_data->nd_region)
> > +		return -EINVAL;
> > +
> > +	dev_info(&scm_data->dev,
> > +		 "Onlining %lluMB of persistent memory\n",
> > +		 nd_mapping_desc.size / SZ_1M);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * allocate_scm_minor() - Allocate a minor number to use for an
> > SCM device
> > + * @scm_data: The SCM device to associate the minor with
> > + * Return: the allocated minor number
> > + */
> > +static int allocate_scm_minor(struct scm_data *scm_data)
> > +{
> > +	int minor;
> > +
> > +	mutex_lock(&minors_idr_lock);
> > +	minor = idr_alloc(&minors_idr, scm_data, 0, SCM_NUM_MINORS,
> > GFP_KERNEL);
> > +	mutex_unlock(&minors_idr_lock);
> > +	return minor;
> > +}
> > +
> > +static void free_scm_minor(struct scm_data *scm_data)
> > +{
> > +	mutex_lock(&minors_idr_lock);
> > +	idr_remove(&minors_idr, MINOR(scm_data->dev.devt));
> > +	mutex_unlock(&minors_idr_lock);
> > +}
> > +
> > +/**
> > + * free_scm() - Free all members of an SCM struct
> > + * @scm_data: the SCM metadata to clear
> > + */
> > +static void free_scm(struct scm_data *scm_data)
> > +{
> > +	int rc;
> > +
> > +	if (scm_data->nvdimm_bus)
> > +		nvdimm_bus_unregister(scm_data->nvdimm_bus);
> > +
> > +	free_scm_minor(scm_data);
> > +
> > +	if (scm_data->metadata_addr)
> > +		devm_memunmap(&scm_data->dev, scm_data->metadata_addr);
> > +
> > +	if (scm_data->ocxl_context) {
> > +		rc = ocxl_context_detach(scm_data->ocxl_context);
> > +		if (rc == -EBUSY)
> > +			dev_warn(&scm_data->dev, "Timeout detaching
> > ocxl context\n");
> > +		else
> > +			ocxl_context_free(scm_data->ocxl_context);
> > +
> > +	}
> > +
> > +	if (scm_data->ocxl_afu)
> > +		ocxl_afu_put(scm_data->ocxl_afu);
> > +
> > +	if (scm_data->ocxl_fn)
> > +		ocxl_function_close(scm_data->ocxl_fn);
> > +
> > +	kfree(scm_data);
> > +}
> > +
> > +/**
> > + * free_scm_dev - Free an SCM device
> > + * @dev: The device struct
> > + */
> > +static void free_scm_dev(struct device *dev)
> > +{
> > +	struct scm_data *scm_data = container_of(dev, struct scm_data,
> > dev);
> > +
> > +	free_scm(scm_data);
> > +}
> > +
> > +/**
> > + * scm_register - Register an SCM device with the kernel
> > + * @scm_data: the SCM metadata
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int scm_register(struct scm_data *scm_data)
> > +{
> > +	int rc;
> > +	int minor = allocate_scm_minor(scm_data);
> > +
> > +	if (minor < 0)
> > +		return minor;
> > +
> > +	scm_data->dev.release = free_scm_dev;
> > +	rc = dev_set_name(&scm_data->dev, "ocxl-scm%d", minor);
> > +	if (rc < 0)
> > +		return rc;
> > +
> > +	scm_data->dev.devt = MKDEV(MAJOR(scm_dev), minor);
> > +	scm_data->dev.class = scm_class;
> > +	scm_data->dev.parent = &scm_data->pdev->dev;
> > +
> > +	rc = device_register(&scm_data->dev);
> > +	return rc;
> 	return device_register(&scm_data->dev);
> 
> Assuming nothing else is added inbetween in later patches...
> If it is then ignore this one.
> 
Ok

> > +}
> > +
> > +/**
> > + * scm_remove() - Free an OpenCAPI Storage Class Memory device
> > + * @pdev: the PCI device information struct
> > + */
> > +static void scm_remove(struct pci_dev *pdev)
> > +{
> > +	if (PCI_FUNC(pdev->devfn) == 0) {
> > +		struct scm_function_0 *scm_func_0 =
> > pci_get_drvdata(pdev);
> > +
> > +		if (scm_func_0) {
> > +			ocxl_function_close(scm_func_0->ocxl_fn);
> > +			scm_func_0->ocxl_fn = NULL;
> > +		}
> > +	} else {
> > +		struct scm_data *scm_data = pci_get_drvdata(pdev);
> > +
> > +		if (scm_data)
> > +			device_unregister(&scm_data->dev);
> > +	}
> > +}
> > +
> > +/**
> > + * scm_probe_function_0 - Set up function 0 for an OpenCAPI
> > Storage Class Memory device
> Overly long line + not consistent on () after function name.
> 
> IIRC either () or not is fine, but should be consistent in a gven
> file.

Ok
> 
> > + * This is important as it enables templates higher than 0 across
> > all other functions,
> > + * which in turn enables higher bandwidth accesses
> > + * which in turn enables higher bandwidth accesses
> 
> Repeated line.
Ok
> 
> > + * @pdev: the PCI device information struct
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int scm_probe_function_0(struct pci_dev *pdev)
> > +{
> > +	struct scm_function_0 *scm_func_0 = NULL;
> > +	struct ocxl_fn *fn;
> > +
> > +	scm_func_0 = kzalloc(sizeof(*scm_func_0), GFP_KERNEL);
> > +	if (!scm_func_0)
> > +		return -ENOMEM;
> > +
> > +	scm_func_0->pdev = pdev;
> > +	fn = ocxl_function_open(pdev);
> > +	if (IS_ERR(fn)) {
> > +		kfree(scm_func_0);
> > +		dev_err(&pdev->dev, "failed to open OCXL function\n");
> > +		return PTR_ERR(fn);
> > +	}
> > +	scm_func_0->ocxl_fn = fn;
> > +
> > +	pci_set_drvdata(pdev, scm_func_0);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * scm_probe - Init an OpenCAPI Storage Class Memory device
> > + * @pdev: the PCI device information struct
> > + * @ent: The entry from scm_pci_tbl
> > + * Return: 0 on success, negative on failure
> > + */
> > +static int scm_probe(struct pci_dev *pdev, const struct
> > pci_device_id *ent)
> > +{
> > +	struct scm_data *scm_data = NULL;
> 
> Always set in paths that use it.
Ok

> 
> > +
> > +	if (PCI_FUNC(pdev->devfn) == 0)
> > +		return scm_probe_function_0(pdev);
> > +	else if (PCI_FUNC(pdev->devfn) != 1)
> > +		return 0;
> > +
> > +	scm_data = kzalloc(sizeof(*scm_data), GFP_KERNEL);
> > +	if (!scm_data) {
> > +		dev_err(&pdev->dev, "Could not allocate SCM
> > metadata\n");
> > +		goto err;
> > +	}
> > +	scm_data->pdev = pdev;
> > +
> > +	pci_set_drvdata(pdev, scm_data);
> > +
> > +	scm_data->ocxl_fn = ocxl_function_open(pdev);
> > +	if (IS_ERR(scm_data->ocxl_fn)) {
> > +		kfree(scm_data);
> > +		scm_data = NULL;
> 
> Doesn't seem like scm_data is used anywhere in the rror path..
Ok
> 
> > +		pci_set_drvdata(pdev, NULL);
> > +		dev_err(&pdev->dev, "failed to open OCXL function\n");
> > +		goto err;
> > +	}
> > +
> > +	scm_data->ocxl_afu = ocxl_function_fetch_afu(scm_data->ocxl_fn, 
> > 0);
> > +	if (scm_data->ocxl_afu == NULL) {
> > +		dev_err(&pdev->dev, "Could not get OCXL AFU from
> > function\n");
> > +		goto err;
> 
> The comment below suggests to me that free_scm will only be called if
> we succeed
> in scm_register?  If so isn't there more error handling to be done
> until that
> happens?
> 

I've moved that comment up - once device_register has been called (even
if the call fails), the free handler should always be called via
device_put.

> > +	}
> > +
> > +	ocxl_afu_get(scm_data->ocxl_afu);
> > +
> > +	if (scm_register(scm_data) < 0) {
> > +		dev_err(&pdev->dev, "Could not register SCM device with
> > the kernel\n");
> > +		goto err;
> > +	}
> > +
> > +	// Resources allocated below here are cleaned up in the release
> > handler
> > +
> > +	if (ocxl_context_alloc(&scm_data->ocxl_context, scm_data-
> > >ocxl_afu, NULL)) {
> > +		dev_err(&pdev->dev, "Could not allocate OCXL
> > context\n");
> > +		goto err;
> > +	}
> > +
> > +	if (ocxl_context_attach(scm_data->ocxl_context, 0, NULL)) {
> > +		dev_err(&pdev->dev, "Could not attach ocxl context\n");
> > +		goto err;
> > +	}
> > +
> > +	if (scm_register_lpc_mem(scm_data)) {
> > +		dev_err(&pdev->dev, "Could not register OCXL SCM memory
> > with libnvdimm\n");
> > +		goto err;
> > +	}
> > +
> > +	return 0;
> > +
> > +err:
> > +	/*
> > +	 * Further cleanup is done in the release handler via
> > free_scm()
> > +	 * This allows us to keep the character device live to handle
> > IOCTLs to
> > +	 * investigate issues if the card has an error
> > +	 */
> > +
> > +	dev_err(&pdev->dev,
> > +		"Error detected, will not register storage class
> > memory\n");
> > +	return -ENXIO;
> 
> Probably better to return more specific errors from the various error
> paths.
> -ENOMEM etc.
> 
I've updated the code to propogate errors up from the calls.

> 
> > +}
> > +
> > +static struct pci_driver scm_pci_driver = {
> > +	.name = "ocxl-scm",
> > +	.id_table = scm_pci_tbl,
> > +	.probe = scm_probe,
> > +	.remove = scm_remove,
> > +	.shutdown = scm_remove,
> > +};
> > +
> > +static int __init scm_init(void)
> > +{
> > +	int rc = 0;
> > +
> > +	rc = pci_register_driver(&scm_pci_driver);
> > +	if (rc)
> > +		return rc;
> > +
> > +	return 0;
> > +}
> > +
> > +static void scm_exit(void)
> > +{
> > +	pci_unregister_driver(&scm_pci_driver);
> > +}
> > +
> > +module_init(scm_init);
> > +module_exit(scm_exit);
> > +
> > +MODULE_DESCRIPTION("Storage Class Memory");
> > +MODULE_LICENSE("GPL");
> > diff --git a/drivers/nvdimm/ocxl/scm_internal.h
> > b/drivers/nvdimm/ocxl/scm_internal.h
> > new file mode 100644
> > index 000000000000..6340012e0f8a
> > --- /dev/null
> > +++ b/drivers/nvdimm/ocxl/scm_internal.h
> > @@ -0,0 +1,28 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +// Copyright 2019 IBM Corp.
> > +
> > +#include <linux/pci.h>
> > +#include <misc/ocxl.h>
> > +#include <linux/libnvdimm.h>
> > +#include <linux/mm.h>
> > +
> > +#define SCM_LABEL_AREA_SIZE	(1UL << PA_SECTION_SHIFT)
> > +
> > +struct scm_function_0 {
> > +	struct pci_dev *pdev;
> > +	struct ocxl_fn *ocxl_fn;
> > +};
> > +
> > +struct scm_data {
> > +	struct device dev;
> > +	struct pci_dev *pdev;
> > +	struct ocxl_fn *ocxl_fn;
> > +	struct nd_interleave_set nd_set;
> > +	struct nvdimm_bus_descriptor bus_desc;
> > +	struct nvdimm_bus *nvdimm_bus;
> > +	struct ocxl_afu *ocxl_afu;
> > +	struct ocxl_context *ocxl_context;
> > +	void *metadata_addr;
> > +	struct resource scm_res;
> > +	struct nd_region *nd_region;
> > +};
-- 
Alastair D'Silva
Open Source Developer
Linux Technology Centre, IBM Australia
mob: 0423 762 819

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