[PATCH 07/13] cxl/acpi: Handle 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.

All decoders manage a host physical address space while active. Only the
root decoder has constraints on location and size. As a result, it makes
most sense for the root decoder to be responsible for managing the
entire address space, and mid-level decoders and endpoints can ask the
root decoder for suballocations.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
 drivers/cxl/acpi.c   | 30 ++++++++++++++++++++++++++++++
 drivers/cxl/cxl.h    |  2 ++
 drivers/cxl/region.c | 12 ++++++------
 3 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index 4c746a6ef48c..a7ce0d660b34 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright(c) 2021 Intel Corporation. All rights reserved. */
 #include <linux/platform_device.h>
+#include <linux/genalloc.h>
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
@@ -73,6 +74,27 @@ static int cxl_acpi_cfmws_verify(struct device *dev,
 	return 0;
 }
 
+/*
+ * Every decoder while active has an address space that it is decoding. However,
+ * only the root level decoders have fixed host physical address space ranges.
+ */
+static int cxl_create_cfmws_address_space(struct cxl_decoder *cxld,
+					  struct acpi_cedt_cfmws *cfmws)
+{
+	const int order = ilog2(SZ_256M * cxld->interleave_ways);
+	struct device *dev = &cxld->dev;
+	struct gen_pool *pool;
+
+	pool = devm_gen_pool_create(dev, order, NUMA_NO_NODE, dev_name(dev));
+	if (IS_ERR(pool))
+		return PTR_ERR(pool);
+
+	cxld->address_space = pool;
+
+	return gen_pool_add(cxld->address_space, cfmws->base_hpa,
+			    cfmws->window_size, NUMA_NO_NODE);
+}
+
 struct cxl_cfmws_context {
 	struct device *dev;
 	struct cxl_port *root_port;
@@ -113,6 +135,14 @@ static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
 	cxld->interleave_ways = CFMWS_INTERLEAVE_WAYS(cfmws);
 	cxld->interleave_granularity = CFMWS_INTERLEAVE_GRANULARITY(cfmws);
 
+	rc = cxl_create_cfmws_address_space(cxld, cfmws);
+	if (rc) {
+		dev_err(dev,
+			"Failed to create CFMWS address space for decoder\n");
+		put_device(&cxld->dev);
+		return 0;
+	}
+
 	rc = cxl_decoder_add(cxld, target_map);
 	if (rc)
 		put_device(&cxld->dev);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index b318cabfc4a2..19e65ed35796 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -207,6 +207,7 @@ enum cxl_decoder_type {
  * @target_type: accelerator vs expander (type2 vs type3) selector
  * @flags: memory type capabilities and locking
  * @region_ida: allocator for region ids.
+ * @address_space: Used/free address space for regions.
  * @nr_targets: number of elements in @target
  * @target: active ordered target list in current decoder configuration
  */
@@ -222,6 +223,7 @@ struct cxl_decoder {
 	enum cxl_decoder_type target_type;
 	unsigned long flags;
 	struct ida region_ida;
+	struct gen_pool *address_space;
 	const int nr_targets;
 	struct cxl_dport *target[];
 };
diff --git a/drivers/cxl/region.c b/drivers/cxl/region.c
index 9174925b67e3..b458d7b97120 100644
--- a/drivers/cxl/region.c
+++ b/drivers/cxl/region.c
@@ -126,7 +126,7 @@ static bool find_cdat_dsmas(const struct cxl_region *region)
 
 /**
  * qtg_match() - Does this CFMWS have desirable QTG for the endpoint
- * @cfmws: The CFMWS for the region
+ * @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
@@ -134,7 +134,7 @@ static bool find_cdat_dsmas(const struct cxl_region *region)
  *
  * Returns true if the QTG ID of the CFMWS matches the endpoint
  */
-static bool qtg_match(const struct cxl_decoder *cfmws,
+static bool qtg_match(const struct cxl_decoder *rootd,
 		      const struct cxl_memdev *endpoint)
 {
 	/* TODO: */
@@ -143,7 +143,7 @@ static bool qtg_match(const struct cxl_decoder *cfmws,
 
 /**
  * region_xhb_config_valid() - determine cross host bridge validity
- * @cfmws: The CFMWS to check against
+ * @rootd: The root decoder to check against
  * @region: The region being programmed
  *
  * The algorithm is outlined in 2.13.14 "Verify XHB configuration sequence" of
@@ -152,7 +152,7 @@ static bool qtg_match(const struct cxl_decoder *cfmws,
  * Returns true if the configuration is valid.
  */
 static bool region_xhb_config_valid(const struct cxl_region *region,
-				    const struct cxl_decoder *cfmws)
+				    const struct cxl_decoder *rootd)
 {
 	/* TODO: */
 	return true;
@@ -160,7 +160,7 @@ static bool region_xhb_config_valid(const struct cxl_region *region,
 
 /**
  * region_hb_rp_config_valid() - determine root port ordering is correct
- * @cfmws: CFMWS decoder for this @region
+ * @rootd: root decoder for this @region
  * @region: Region to validate
  *
  * The algorithm is outlined in 2.13.15 "Verify HB root port configuration
@@ -169,7 +169,7 @@ static bool region_xhb_config_valid(const struct cxl_region *region,
  * Returns true if the configuration is valid.
  */
 static bool region_hb_rp_config_valid(const struct cxl_region *region,
-				      const struct cxl_decoder *cfmws)
+				      const struct cxl_decoder *rootd)
 {
 	/* TODO: */
 	return true;
-- 
2.34.1