[PATCH 6/6] cxl/region: Handle region's address space allocation

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

Regions are carved out of an addresses space which is claimed by top
level decoders, and subsequently their children decoders. Regions are
created with a size and therefore must fit, with proper alignment, in
that address space. The support for doing this fitting is handled by the
driver automatically.

As an example, a platform might configure a top level decoder to claim
1TB of address space @ 0x800000000 -> 0x10800000000; it would be
possible to create M regions with appropriate alignment to occupy that
address space. Each of those regions would have a host physical address
somewhere in the range between 32G and 1.3TB, and the location will be
determined by the logic added here.

The request_region() usage is not strictly mandatory at this point as
the actual handling of the address space is done with genpools. It is
highly likely however that the resource/region APIs will become useful
in the not too distant future.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
 drivers/cxl/core.c   | 13 +++++++++++++
 drivers/cxl/cxl.h    |  2 ++
 drivers/cxl/region.c | 31 +++++++++++++++++++++++++++++--
 3 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/core.c b/drivers/cxl/core.c
index 0e598a18e95f..b57ee627bc6a 100644
--- a/drivers/cxl/core.c
+++ b/drivers/cxl/core.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright(c) 2020 Intel Corporation. All rights reserved. */
 #include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/genalloc.h>
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/pci.h>
@@ -607,6 +608,18 @@ devm_cxl_add_decoder(struct device *host, struct cxl_port *port, int nr_targets,
 	rc = devm_add_action_or_reset(host, unregister_dev, dev);
 	if (rc)
 		return ERR_PTR(rc);
+
+	cxld->address_space =
+		devm_gen_pool_create(dev, ilog2(SZ_256M * cxld->interleave_ways),
+				     NUMA_NO_NODE, dev_name(dev));
+	if (IS_ERR(cxld->address_space))
+		return ERR_CAST(cxld->address_space);
+
+	rc = gen_pool_add(cxld->address_space, cxld->res.start,
+			  resource_size(&cxld->res), NUMA_NO_NODE);
+	if (rc)
+		return ERR_PTR(rc);
+
 	return cxld;
 
 err:
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index b08f0969abeb..b5b728155d86 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -193,6 +193,7 @@ enum cxl_decoder_type {
  * @region_ida: allocator for region ids.
  * @regions: List of regions mapped (may be disabled) by this decoder.
  * @youngest: Last region created for this decoder.
+ * @address_space: Used/free address space for regions.
  * @target: active ordered target list in current decoder configuration
  */
 struct cxl_decoder {
@@ -206,6 +207,7 @@ struct cxl_decoder {
 	struct ida region_ida;
 	struct list_head regions;
 	struct cxl_region *youngest;
+	struct gen_pool *address_space;
 	struct cxl_dport *target[];
 };
 
diff --git a/drivers/cxl/region.c b/drivers/cxl/region.c
index 62bca8b30349..0554f3fff7ac 100644
--- a/drivers/cxl/region.c
+++ b/drivers/cxl/region.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright(c) 2021 Intel Corporation. All rights reserved. */
 #include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/genalloc.h>
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/sizes.h>
@@ -388,9 +389,33 @@ int cxl_delete_region(struct cxl_decoder *cxld, const char *region_name)
 	return 0;
 }
 
+static int allocate_region_addr(struct cxl_region *region)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(region->dev.parent);
+	unsigned long start;
+
+	start = gen_pool_alloc(cxld->address_space, region->requested_size);
+	if (!start) {
+		trace_cxl_region_bind(region, "Couldn't allocate address space");
+		return -ENOMEM;
+	}
+
+	region->res =
+		__request_region(&cxld->res, start, region->requested_size,
+				 dev_name(&region->dev), IORESOURCE_EXCLUSIVE);
+	if (IS_ERR(region->res)) {
+		trace_cxl_region_bind(region, "Couldn't obtain region");
+		gen_pool_free(cxld->address_space, start,
+			      region->requested_size);
+		return PTR_ERR(region->res);
+	}
+
+	return 0;
+}
+
 static int bind_region(struct cxl_region *region)
 {
-	int i;
+	int i, rc;
 
 	if (dev_WARN_ONCE(&region->dev, !cxl_is_region_configured(region),
 			  "unconfigured regions can't be probed (race?)\n")) {
@@ -408,7 +433,9 @@ static int bind_region(struct cxl_region *region)
 			return -ENXIO;
 		}
 
-	/* TODO: Allocate from decoder's address space */
+	rc = allocate_region_addr(region);
+	if (rc)
+		return rc;
 
 	/* TODO: program HDM decoders */
 
-- 
2.32.0