[PATCH v3 04/14] cxl/region: Introduce a cxl_region driver

[Ben Widawsky <ben.widawsky@intel.com>]

The cxl_region driver is responsible for managing the HDM decoder
programming in the CXL topology. Once a region is created it must be
configured and bound to the driver in order to activate it.

The following is a sample of how such controls might work:

region=$(cat /sys/bus/cxl/devices/decoder0.0/create_region)
echo $region > /sys/bus/cxl/devices/decoder0.0/create_region
echo 2 > /sys/bus/cxl/devices/decoder0.0/region0.0:0/interleave
echo $((256<<20)) > /sys/bus/cxl/devices/decoder0.0/region0.0:0/size
echo mem0 > /sys/bus/cxl/devices/decoder0.0/region0.0:0/target0
echo mem1 > /sys/bus/cxl/devices/decoder0.0/region0.0:0/target1
echo region0.0:0 > /sys/bus/cxl/drivers/cxl_region/bind

In order to handle the eventual rise in failure modes of binding a
region, a new trace event is created to help track these failures for
debug and reconfiguration paths in userspace.

Reported-by: kernel test robot <lkp@intel.com> (v2)
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
Changes since v2:
- Add CONFIG_CXL_REGION
- Check ways/granularity in sanitize
---
 .../driver-api/cxl/memory-devices.rst         |   3 +
 drivers/cxl/Kconfig                           |   4 +
 drivers/cxl/Makefile                          |   2 +
 drivers/cxl/core/core.h                       |   1 +
 drivers/cxl/core/port.c                       |  17 +-
 drivers/cxl/core/region.c                     |  25 +-
 drivers/cxl/cxl.h                             |  31 ++
 drivers/cxl/region.c                          | 349 ++++++++++++++++++
 drivers/cxl/region.h                          |   4 +
 9 files changed, 431 insertions(+), 5 deletions(-)
 create mode 100644 drivers/cxl/region.c

diff --git a/Documentation/driver-api/cxl/memory-devices.rst b/Documentation/driver-api/cxl/memory-devices.rst
index 66ddc58a21b1..8cb4dece5b17 100644
--- a/Documentation/driver-api/cxl/memory-devices.rst
+++ b/Documentation/driver-api/cxl/memory-devices.rst
@@ -364,6 +364,9 @@ CXL Core
 
 CXL Regions
 -----------
+.. kernel-doc:: drivers/cxl/region.c
+   :doc: cxl region
+
 .. kernel-doc:: drivers/cxl/region.h
    :identifiers:
 
diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
index b88ab956bb7c..742847503c16 100644
--- a/drivers/cxl/Kconfig
+++ b/drivers/cxl/Kconfig
@@ -98,4 +98,8 @@ config CXL_PORT
 	default CXL_BUS
 	tristate
 
+config CXL_REGION
+	default CXL_PORT
+	tristate
+
 endif
diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile
index ce267ef11d93..02a4776e7ab9 100644
--- a/drivers/cxl/Makefile
+++ b/drivers/cxl/Makefile
@@ -5,9 +5,11 @@ obj-$(CONFIG_CXL_MEM) += cxl_mem.o
 obj-$(CONFIG_CXL_ACPI) += cxl_acpi.o
 obj-$(CONFIG_CXL_PMEM) += cxl_pmem.o
 obj-$(CONFIG_CXL_PORT) += cxl_port.o
+obj-$(CONFIG_CXL_REGION) += cxl_region.o
 
 cxl_mem-y := mem.o
 cxl_pci-y := pci.o
 cxl_acpi-y := acpi.o
 cxl_pmem-y := pmem.o
 cxl_port-y := port.o
+cxl_region-y := region.o
diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 35fd08d560e2..b8a154da34df 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -7,6 +7,7 @@
 extern const struct device_type cxl_nvdimm_bridge_type;
 extern const struct device_type cxl_nvdimm_type;
 extern const struct device_type cxl_memdev_type;
+extern const struct device_type cxl_region_type;
 
 extern struct attribute_group cxl_base_attribute_group;
 
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 0826208b2bdf..0847e6ce19ef 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -9,6 +9,7 @@
 #include <linux/idr.h>
 #include <cxlmem.h>
 #include <cxlpci.h>
+#include <region.h>
 #include <cxl.h>
 #include "core.h"
 
@@ -49,6 +50,8 @@ static int cxl_device_id(struct device *dev)
 	}
 	if (dev->type == &cxl_memdev_type)
 		return CXL_DEVICE_MEMORY_EXPANDER;
+	if (dev->type == &cxl_region_type)
+		return CXL_DEVICE_REGION;
 	return 0;
 }
 
@@ -1425,13 +1428,23 @@ static int cxl_bus_match(struct device *dev, struct device_driver *drv)
 
 static int cxl_bus_probe(struct device *dev)
 {
-	int rc;
+	int id = cxl_device_id(dev);
+	int rc = -ENODEV;
 
 	cxl_nested_lock(dev);
-	rc = to_cxl_drv(dev->driver)->probe(dev);
+	if (id == CXL_DEVICE_REGION) {
+		/* Regions cannot bind until parameters are set */
+		struct cxl_region *cxlr = to_cxl_region(dev);
+
+		if (is_cxl_region_configured(cxlr))
+			rc = to_cxl_drv(dev->driver)->probe(dev);
+	} else {
+		rc = to_cxl_drv(dev->driver)->probe(dev);
+	}
 	cxl_nested_unlock(dev);
 
 	dev_dbg(dev, "probe: %d\n", rc);
+
 	return rc;
 }
 
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 3b48e0469fc7..784e4ba25128 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -12,6 +12,8 @@
 #include <cxl.h>
 #include "core.h"
 
+#include "core.h"
+
 /**
  * DOC: cxl core region
  *
@@ -26,10 +28,27 @@ static const struct attribute_group region_interleave_group;
 
 static bool is_region_active(struct cxl_region *cxlr)
 {
-	/* TODO: Regions can't be activated yet. */
-	return false;
+	return cxlr->active;
 }
 
+/*
+ * Most sanity checking is left up to region binding. This does the most basic
+ * check to determine whether or not the core should try probing the driver.
+ */
+bool is_cxl_region_configured(const struct cxl_region *cxlr)
+{
+	/* zero sized regions aren't a thing. */
+	if (cxlr->config.size <= 0)
+		return false;
+
+	/* all regions have at least 1 target */
+	if (!cxlr->config.targets[0])
+		return false;
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(is_cxl_region_configured);
+
 static void remove_target(struct cxl_region *cxlr, int target)
 {
 	struct cxl_memdev *cxlmd;
@@ -316,7 +335,7 @@ static const struct attribute_group *region_groups[] = {
 
 static void cxl_region_release(struct device *dev);
 
-static const struct device_type cxl_region_type = {
+const struct device_type cxl_region_type = {
 	.name = "cxl_region",
 	.release = cxl_region_release,
 	.groups = region_groups
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index b9f0099c1f39..d1a8ca19c9ea 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -81,6 +81,31 @@ static inline int cxl_to_interleave_ways(u8 eniw)
 	}
 }
 
+static inline bool cxl_is_interleave_ways_valid(int iw)
+{
+	switch (iw) {
+		case 0 ... 4:
+		case 6:
+		case 8:
+		case 12:
+		case 16:
+			return true;
+		default:
+			return false;
+	}
+
+	unreachable();
+}
+
+static inline bool cxl_is_interleave_granularity_valid(int ig)
+{
+	if (!is_power_of_2(ig))
+		return false;
+
+	/* 16K is the max */
+	return ((ig >> 15) == 0);
+}
+
 /* CXL 2.0 8.2.8.1 Device Capabilities Array Register */
 #define CXLDEV_CAP_ARRAY_OFFSET 0x0
 #define   CXLDEV_CAP_ARRAY_CAP_ID 0
@@ -199,6 +224,10 @@ void __iomem *devm_cxl_iomap_block(struct device *dev, resource_size_t addr,
 #define CXL_DECODER_F_ENABLE    BIT(5)
 #define CXL_DECODER_F_MASK  GENMASK(5, 0)
 
+#define cxl_is_pmem_t3(flags)                                                  \
+	(((flags) & (CXL_DECODER_F_TYPE3 | CXL_DECODER_F_PMEM)) ==             \
+	 (CXL_DECODER_F_TYPE3 | CXL_DECODER_F_PMEM))
+
 enum cxl_decoder_type {
        CXL_DECODER_ACCELERATOR = 2,
        CXL_DECODER_EXPANDER = 3,
@@ -357,6 +386,7 @@ struct cxl_dport *devm_cxl_add_dport(struct cxl_port *port,
 				     resource_size_t component_reg_phys);
 struct cxl_dport *cxl_find_dport_by_dev(struct cxl_port *port,
 					const struct device *dev);
+struct cxl_port *ep_find_cxl_port(struct cxl_memdev *cxlmd, unsigned int depth);
 
 struct cxl_decoder *to_cxl_decoder(struct device *dev);
 bool is_root_decoder(struct device *dev);
@@ -404,6 +434,7 @@ void cxl_driver_unregister(struct cxl_driver *cxl_drv);
 #define CXL_DEVICE_PORT			3
 #define CXL_DEVICE_ROOT			4
 #define CXL_DEVICE_MEMORY_EXPANDER	5
+#define CXL_DEVICE_REGION		6
 
 #define MODULE_ALIAS_CXL(type) MODULE_ALIAS("cxl:t" __stringify(type) "*")
 #define CXL_MODALIAS_FMT "cxl:t%d"
diff --git a/drivers/cxl/region.c b/drivers/cxl/region.c
new file mode 100644
index 000000000000..cc41939a2f0a
--- /dev/null
+++ b/drivers/cxl/region.c
@@ -0,0 +1,349 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2021 Intel Corporation. All rights reserved. */
+#include <linux/platform_device.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include "cxlmem.h"
+#include "region.h"
+#include "cxl.h"
+
+/**
+ * DOC: cxl region
+ *
+ * This module implements a region driver that is capable of programming CXL
+ * hardware to setup regions.
+ *
+ * A CXL region encompasses a chunk of host physical address space that may be
+ * consumed by a single device (x1 interleave aka linear) or across multiple
+ * devices (xN interleaved). The region driver has the following
+ * responsibilities:
+ *
+ * * Walk topology to obtain decoder resources for region configuration.
+ * * Program decoder resources based on region configuration.
+ * * Bridge CXL regions to LIBNVDIMM
+ * * Initiates reading and configuring LSA regions
+ * * Enumerates regions created by BIOS (typically volatile)
+ */
+
+#define region_ways(region) ((region)->config.interleave_ways)
+#define region_granularity(region) ((region)->config.interleave_granularity)
+
+static struct cxl_decoder *rootd_from_region(struct cxl_region *cxlr)
+{
+	struct device *d = cxlr->dev.parent;
+
+	if (WARN_ONCE(!is_root_decoder(d),
+		      "Corrupt topology for root region\n"))
+		return NULL;
+
+	return to_cxl_decoder(d);
+}
+
+static struct cxl_port *get_hostbridge(const struct cxl_memdev *ep)
+{
+	struct cxl_port *port = ep->port;
+
+	while (!is_cxl_root(port)) {
+		port = to_cxl_port(port->dev.parent);
+		if (port->depth == 1)
+			return port;
+	}
+
+	BUG();
+	return NULL;
+}
+
+static struct cxl_port *get_root_decoder(const struct cxl_memdev *endpoint)
+{
+	struct cxl_port *hostbridge = get_hostbridge(endpoint);
+
+	if (hostbridge)
+		return to_cxl_port(hostbridge->dev.parent);
+
+	return NULL;
+}
+
+/**
+ * sanitize_region() - Check is region is reasonably configured
+ * @cxlr: The region to check
+ *
+ * Determination as to whether or not a region can possibly be configured is
+ * described in CXL Memory Device SW Guide. In order to implement the algorithms
+ * described there, certain more basic configuration parameters must first need
+ * to be validated. That is accomplished by this function.
+ *
+ * Returns 0 if the region is reasonably configured, else returns a negative
+ * error code.
+ */
+static int sanitize_region(const struct cxl_region *cxlr)
+{
+	const int ig = region_granularity(cxlr);
+	const int iw = region_ways(cxlr);
+	int i;
+
+	if (dev_WARN_ONCE(&cxlr->dev, !is_cxl_region_configured(cxlr),
+			  "unconfigured regions can't be probed (race?)\n")) {
+		return -ENXIO;
+	}
+
+	/*
+	 * Interleave attributes should be caught by later math, but it's
+	 * easiest to find those issues here, now.
+	 */
+	if (!cxl_is_interleave_ways_valid(iw)) {
+		dev_dbg(&cxlr->dev, "Invalid number of ways\n");
+		return -ENXIO;
+	}
+
+	if (!cxl_is_interleave_granularity_valid(ig)) {
+		dev_dbg(&cxlr->dev, "Invalid interleave granularity\n");
+		return -ENXIO;
+	}
+
+	if (cxlr->config.size % (SZ_256M * iw)) {
+		dev_dbg(&cxlr->dev, "Invalid size. Must be multiple of %uM\n",
+			256 * iw);
+		return -ENXIO;
+	}
+
+	for (i = 0; i < iw; i++) {
+		if (!cxlr->config.targets[i]) {
+			dev_dbg(&cxlr->dev, "Missing memory device target%u",
+				i);
+			return -ENXIO;
+		}
+		if (!cxlr->config.targets[i]->dev.driver) {
+			dev_dbg(&cxlr->dev, "%s isn't CXL.mem capable\n",
+				dev_name(&cxlr->config.targets[i]->dev));
+			return -ENODEV;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * allocate_address_space() - Gets address space for the region.
+ * @cxlr: The region that will consume the address space
+ */
+static int allocate_address_space(struct cxl_region *cxlr)
+{
+	/* TODO */
+	return 0;
+}
+
+/**
+ * find_cdat_dsmas() - Find a valid DSMAS for the region
+ * @cxlr: The region
+ */
+static bool find_cdat_dsmas(const struct cxl_region *cxlr)
+{
+	return true;
+}
+
+/**
+ * qtg_match() - Does this root decoder have desirable QTG for the endpoint
+ * @rootd: The root decoder for the region
+ * @endpoint: Endpoint whose QTG is being compared
+ *
+ * Prior to calling this function, the caller should verify that all endpoints
+ * in the region have the same QTG ID.
+ *
+ * Returns true if the QTG ID of the root decoder matches the endpoint
+ */
+static bool qtg_match(const struct cxl_decoder *rootd,
+		      const struct cxl_memdev *endpoint)
+{
+	/* TODO: */
+	return true;
+}
+
+/**
+ * region_xhb_config_valid() - determine cross host bridge validity
+ * @cxlr: The region being programmed
+ * @rootd: The root decoder to check against
+ *
+ * The algorithm is outlined in 2.13.14 "Verify XHB configuration sequence" of
+ * the CXL Memory Device SW Guide (Rev1p0).
+ *
+ * Returns true if the configuration is valid.
+ */
+static bool region_xhb_config_valid(const struct cxl_region *cxlr,
+				    const struct cxl_decoder *rootd)
+{
+	/* TODO: */
+	return true;
+}
+
+/**
+ * region_hb_rp_config_valid() - determine root port ordering is correct
+ * @cxlr: Region to validate
+ * @rootd: root decoder for this @cxlr
+ *
+ * The algorithm is outlined in 2.13.15 "Verify HB root port configuration
+ * sequence" of the CXL Memory Device SW Guide (Rev1p0).
+ *
+ * Returns true if the configuration is valid.
+ */
+static bool region_hb_rp_config_valid(const struct cxl_region *cxlr,
+				      const struct cxl_decoder *rootd)
+{
+	/* TODO: */
+	return true;
+}
+
+/**
+ * rootd_contains() - determine if this region can exist in the root decoder
+ * @rootd: root decoder that potentially decodes to this region
+ * @cxlr: region to be routed by the @rootd
+ */
+static bool rootd_contains(const struct cxl_region *cxlr,
+			   const struct cxl_decoder *rootd)
+{
+	/* TODO: */
+	return true;
+}
+
+static bool rootd_valid(const struct cxl_region *cxlr,
+			const struct cxl_decoder *rootd)
+{
+	const struct cxl_memdev *endpoint = cxlr->config.targets[0];
+
+	if (!qtg_match(rootd, endpoint))
+		return false;
+
+	if (!cxl_is_pmem_t3(rootd->flags))
+		return false;
+
+	if (!region_xhb_config_valid(cxlr, rootd))
+		return false;
+
+	if (!region_hb_rp_config_valid(cxlr, rootd))
+		return false;
+
+	if (!rootd_contains(cxlr, rootd))
+		return false;
+
+	return true;
+}
+
+struct rootd_context {
+	const struct cxl_region *cxlr;
+	struct cxl_port *hbs[CXL_DECODER_MAX_INTERLEAVE];
+	int count;
+};
+
+static int rootd_match(struct device *dev, void *data)
+{
+	struct rootd_context *ctx = (struct rootd_context *)data;
+	const struct cxl_region *cxlr = ctx->cxlr;
+
+	if (!is_root_decoder(dev))
+		return 0;
+
+	return !!rootd_valid(cxlr, to_cxl_decoder(dev));
+}
+
+/*
+ * This is a roughly equivalent implementation to "Figure 45 - High-level
+ * sequence: Finding CFMWS for region" from the CXL Memory Device SW Guide
+ * Rev1p0.
+ */
+static struct cxl_decoder *find_rootd(const struct cxl_region *cxlr,
+				      const struct cxl_port *root)
+{
+	struct rootd_context ctx;
+	struct device *ret;
+
+	ctx.cxlr = cxlr;
+
+	ret = device_find_child((struct device *)&root->dev, &ctx, rootd_match);
+	if (ret)
+		return to_cxl_decoder(ret);
+
+	return NULL;
+}
+
+static int collect_ep_decoders(const struct cxl_region *cxlr)
+{
+	/* TODO: */
+	return 0;
+}
+
+static int bind_region(const struct cxl_region *cxlr)
+{
+	/* TODO: */
+	return 0;
+}
+
+static int cxl_region_probe(struct device *dev)
+{
+	struct cxl_region *cxlr = to_cxl_region(dev);
+	struct cxl_port *root_port;
+	struct cxl_decoder *rootd, *ours;
+	int ret;
+
+	device_lock_assert(&cxlr->dev);
+
+	if (cxlr->active)
+		return 0;
+
+	if (uuid_is_null(&cxlr->config.uuid))
+		uuid_gen(&cxlr->config.uuid);
+
+	/* TODO: What about volatile, and LSA generated regions? */
+
+	ret = sanitize_region(cxlr);
+	if (ret)
+		return ret;
+
+	ret = allocate_address_space(cxlr);
+	if (ret)
+		return ret;
+
+	if (!find_cdat_dsmas(cxlr))
+		return -ENXIO;
+
+	rootd = rootd_from_region(cxlr);
+	if (!rootd) {
+		dev_err(dev, "Couldn't find root decoder\n");
+		return -ENXIO;
+	}
+
+	if (!rootd_valid(cxlr, rootd)) {
+		dev_err(dev, "Picked invalid rootd\n");
+		return -ENXIO;
+	}
+
+	root_port = get_root_decoder(cxlr->config.targets[0]);
+	ours = find_rootd(cxlr, root_port);
+	if (ours != rootd)
+		dev_dbg(dev, "Picked different rootd %s %s\n",
+			dev_name(&rootd->dev), dev_name(&ours->dev));
+	if (ours)
+		put_device(&ours->dev);
+
+	ret = collect_ep_decoders(cxlr);
+	if (ret)
+		return ret;
+
+	ret = bind_region(cxlr);
+	if (!ret) {
+		cxlr->active = true;
+		dev_info(dev, "Bound");
+	}
+
+	return ret;
+}
+
+static struct cxl_driver cxl_region_driver = {
+	.name = "cxl_region",
+	.probe = cxl_region_probe,
+	.id = CXL_DEVICE_REGION,
+};
+module_cxl_driver(cxl_region_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_IMPORT_NS(CXL);
+MODULE_ALIAS_CXL(CXL_DEVICE_REGION);
diff --git a/drivers/cxl/region.h b/drivers/cxl/region.h
index eb1249e3c1d4..00a6dc729c26 100644
--- a/drivers/cxl/region.h
+++ b/drivers/cxl/region.h
@@ -13,6 +13,7 @@
  * @id: This regions id. Id is globally unique across all regions.
  * @list: Node in decoder's region list.
  * @res: Resource this region carves out of the platform decode range.
+ * @active: If the region has been activated.
  * @config: HDM decoder program config
  * @config.size: Size of the region determined from LSA or userspace.
  * @config.uuid: The UUID for this region.
@@ -25,6 +26,7 @@ struct cxl_region {
 	int id;
 	struct list_head list;
 	struct resource *res;
+	bool active;
 
 	struct {
 		u64 size;
@@ -35,4 +37,6 @@ struct cxl_region {
 	} config;
 };
 
+bool is_cxl_region_configured(const struct cxl_region *cxlr);
+
 #endif
-- 
2.35.0