cxl/region: Add region autodiscovery

Region autodiscovery is an asynchronous state machine advanced by
cxl_port_probe(). After the decoders on an endpoint port are enumerated
they are scanned for actively enabled instances. Each active decoder is
flagged for auto-assembly CXL_DECODER_F_AUTO and attached to a region.
If a region does not already exist for the address range setting of the
decoder one is created. That creation process may race with other
decoders of the same region being discovered since cxl_port_probe() is
asynchronous. A new 'struct cxl_root_decoder' lock, @range_lock, is
introduced to mitigate that race.

Once all decoders have arrived, "p->nr_targets == p->interleave_ways",
they are sorted by their relative decode position. The sort algorithm
involves finding the point in the cxl_port topology where one leg of the
decode leads to deviceA and the other deviceB. At that point in the
topology the target order in the 'struct cxl_switch_decoder' indicates
the relative position of those endpoint decoders in the region.

>From that point the region goes through the same setup and validation
steps as user-created regions, but instead of programming the decoders
it validates that driver would have written the same values to the
decoders as were already present.

Tested-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/167601999958.1924368.9366954455835735048.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index ca76879af1de..c8ee4bb8cce6 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -261,6 +261,8 @@ resource_size_t cxl_rcrb_to_component(struct device *dev,
  * cxl_decoder flags that define the type of memory / devices this
  * decoder supports as well as configuration lock status See "CXL 2.0
  * 8.2.5.12.7 CXL HDM Decoder 0 Control Register" for details.
+ * Additionally indicate whether decoder settings were autodetected,
+ * user customized.
  */
 #define CXL_DECODER_F_RAM   BIT(0)
 #define CXL_DECODER_F_PMEM  BIT(1)
@@ -334,12 +336,22 @@ static inline const char *cxl_decoder_mode_name(enum cxl_decoder_mode mode)
 	return "mixed";
 }
 
+/*
+ * Track whether this decoder is reserved for region autodiscovery, or
+ * free for userspace provisioning.
+ */
+enum cxl_decoder_state {
+	CXL_DECODER_STATE_MANUAL,
+	CXL_DECODER_STATE_AUTO,
+};
+
 /**
  * struct cxl_endpoint_decoder - Endpoint  / SPA to DPA decoder
  * @cxld: base cxl_decoder_object
  * @dpa_res: actively claimed DPA span of this decoder
  * @skip: offset into @dpa_res where @cxld.hpa_range maps
  * @mode: which memory type / access-mode-partition this decoder targets
+ * @state: autodiscovery state
  * @pos: interleave position in @cxld.region
  */
 struct cxl_endpoint_decoder {
@@ -347,6 +359,7 @@ struct cxl_endpoint_decoder {
 	struct resource *dpa_res;
 	resource_size_t skip;
 	enum cxl_decoder_mode mode;
+	enum cxl_decoder_state state;
 	int pos;
 };
 
@@ -380,6 +393,7 @@ typedef struct cxl_dport *(*cxl_calc_hb_fn)(struct cxl_root_decoder *cxlrd,
  * @region_id: region id for next region provisioning event
  * @calc_hb: which host bridge covers the n'th position by granularity
  * @platform_data: platform specific configuration data
+ * @range_lock: sync region autodiscovery by address range
  * @cxlsd: base cxl switch decoder
  */
 struct cxl_root_decoder {
@@ -387,6 +401,7 @@ struct cxl_root_decoder {
 	atomic_t region_id;
 	cxl_calc_hb_fn calc_hb;
 	void *platform_data;
+	struct mutex range_lock;
 	struct cxl_switch_decoder cxlsd;
 };
 
@@ -436,6 +451,13 @@ struct cxl_region_params {
  */
 #define CXL_REGION_F_INCOHERENT 0
 
+/*
+ * Indicate whether this region has been assembled by autodetection or
+ * userspace assembly. Prevent endpoint decoders outside of automatic
+ * detection from being added to the region.
+ */
+#define CXL_REGION_F_AUTO 1
+
 /**
  * struct cxl_region - CXL region
  * @dev: This region's device
@@ -699,6 +721,8 @@ struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct device *dev);
 #ifdef CONFIG_CXL_REGION
 bool is_cxl_pmem_region(struct device *dev);
 struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev);
+int cxl_add_to_region(struct cxl_port *root,
+		      struct cxl_endpoint_decoder *cxled);
 #else
 static inline bool is_cxl_pmem_region(struct device *dev)
 {
@@ -708,6 +732,11 @@ static inline struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev)
 {
 	return NULL;
 }
+static inline int cxl_add_to_region(struct cxl_port *root,
+				    struct cxl_endpoint_decoder *cxled)
+{
+	return 0;
+}
 #endif
 
 /*