[RFC PATCH v2 27/28] cxl/region: Gather HDM decoder resources

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

Prepare for HDM decoder programming by iterating through all components
and obtaining a cxl_decoder for each.

Programming a CXL region to accept memory transactions over a set of
devices requires programming HDM decoders for every component that is
part of the hierarchy enabling the region (host bridges, switches, and
endpoints). For this to be possible, each of these components must have
an available HDM decoder, which is a limited hardware resource.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
 drivers/cxl/core/bus.c |  8 ++++++
 drivers/cxl/cxl.h      |  3 ++
 drivers/cxl/port.c     | 53 ++++++++++++++++++++++++++++++++++
 drivers/cxl/region.c   | 65 +++++++++++++++++++++++++++++++++++++++---
 drivers/cxl/region.h   |  4 +++
 drivers/cxl/trace.h    | 21 ++++++++++++++
 6 files changed, 150 insertions(+), 4 deletions(-)

diff --git a/drivers/cxl/core/bus.c b/drivers/cxl/core/bus.c
index 3042e6e6f5b3..a75fb2c7e094 100644
--- a/drivers/cxl/core/bus.c
+++ b/drivers/cxl/core/bus.c
@@ -327,6 +327,14 @@ static bool is_endpoint_decoder(struct device *dev)
 	return dev->type == &cxl_decoder_endpoint_type;
 }
 
+bool is_cxl_decoder(struct device *dev)
+{
+	return dev->type == &cxl_decoder_switch_type ||
+	       dev->type == &cxl_decoder_endpoint_type ||
+	       dev->type == &cxl_decoder_root_type;
+}
+EXPORT_SYMBOL_GPL(is_cxl_decoder);
+
 bool is_root_decoder(struct device *dev)
 {
 	return dev->type == &cxl_decoder_root_type;
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 63554c9cebf0..79d22992fddf 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -335,11 +335,14 @@ int cxl_add_dport(struct cxl_port *port, struct device *dport, int port_id,
 struct cxl_dport *cxl_get_root_dport(struct device *dev);
 struct cxl_dport *cxl_find_dport_by_dev(struct cxl_port *port,
 					struct device *dev);
+struct cxl_decoder *cxl_pop_decoder(struct cxl_port *port);
+void cxl_push_decoder(struct cxl_decoder *cxld);
 
 struct cxl_decoder *to_cxl_decoder(struct device *dev);
 bool is_root_decoder(struct device *dev);
 struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
 				      unsigned int nr_targets);
+bool is_cxl_decoder(struct device *dev);
 int cxl_decoder_add_locked(struct cxl_decoder *cxld, int *target_map);
 int cxl_decoder_add(struct cxl_decoder *cxld, int *target_map);
 int cxl_decoder_autoremove(struct device *host, struct cxl_decoder *cxld);
diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
index 3ddfd7673a56..5d35ccf2407f 100644
--- a/drivers/cxl/port.c
+++ b/drivers/cxl/port.c
@@ -35,6 +35,59 @@
  * presenting APIs to other drivers to utilize the decoders.
  */
 
+static int unused_decoder(struct device *dev, void *data)
+{
+	struct cxl_decoder *cxld;
+
+	if (!is_cxl_decoder(dev))
+		return 0;
+
+	if (dev_WARN_ONCE(dev, is_root_decoder(dev),
+			  "Root decoders can't be present"))
+		return 0;
+
+	cxld = to_cxl_decoder(dev);
+	if (cxld->flags & CXL_DECODER_F_EN)
+		return 0;
+
+	/*
+	 * Mark this decoder as enabled to prevent other entities from thinking
+	 * it's available.
+	 */
+	cxld->flags |= CXL_DECODER_F_EN;
+
+	return 1;
+}
+
+/**
+ * cxl_pop_decoder() - Obtains an available decoder resource
+ * @port: Owner of the decoder resource
+ */
+struct cxl_decoder *cxl_pop_decoder(struct cxl_port *port)
+{
+	struct device *cxldd;
+
+	cxldd = device_find_child(&port->dev, NULL, unused_decoder);
+	if (!cxldd)
+		return ERR_PTR(-EBUSY);
+
+	/* Keep the reference */
+
+	return to_cxl_decoder(cxldd);
+}
+EXPORT_SYMBOL_GPL(cxl_pop_decoder);
+
+/**
+ * cxl_push_decoder() - Restores decoder resource to the port
+ * @cxld: the decoder resource to replace
+ */
+void cxl_push_decoder(struct cxl_decoder *cxld)
+{
+	cxld->flags &= ~CXL_DECODER_F_EN;
+	put_device(&cxld->dev);
+}
+EXPORT_SYMBOL_GPL(cxl_push_decoder);
+
 struct cxl_port_data {
 	struct cxl_component_regs regs;
 
diff --git a/drivers/cxl/region.c b/drivers/cxl/region.c
index 3276c7243c2a..f4d190ede3ee 100644
--- a/drivers/cxl/region.c
+++ b/drivers/cxl/region.c
@@ -450,9 +450,32 @@ static struct cxl_decoder *find_cfmws(const struct cxl_region *region,
 	return NULL;
 }
 
+static void put_all_decoders(struct decoder_programming *p)
+{
+	int i;
+
+	for (i = 0; i < CXL_DECODER_MAX_INTERLEAVE; i++) {
+		if (p->hbs[i].cxld) {
+			cxl_push_decoder(p->hbs[i].cxld);
+			p->hbs[i].cxld = NULL;
+		}
+
+		if (p->ep_cxld[i]) {
+			cxl_push_decoder(p->ep_cxld[i]);
+			p->ep_cxld[i] = NULL;
+		}
+	}
+}
+
+static void release_decoders(void *p)
+{
+	put_all_decoders(p);
+}
+
 /**
  * gather_hdm_decoders() - Amass all HDM decoders in the hierarchy
  * @region: The region to be programmed
+ * @p: Programming state that will gather decoders
  *
  * Programming the hardware such that the correct set of devices receive the
  * correct memory traffic requires all connected components in the hierarchy to
@@ -461,10 +484,44 @@ static struct cxl_decoder *find_cfmws(const struct cxl_region *region,
  * Returns 0 if an HDM decoder was obtained for each component, else returns a
  * negative error code.
  */
-static int gather_hdm_decoders(const struct cxl_region *region)
+static int gather_hdm_decoders(const struct cxl_region *region, struct decoder_programming *p)
 {
-	/* TODO: */
-	return 0;
+	struct cxl_memdev *ep;
+	struct cxl_port *hbs[CXL_DECODER_MAX_INTERLEAVE];
+	int i, hb_count = get_unique_hostbridges(region, hbs);
+
+	for_each_cxl_endpoint(ep, region, i) {
+		struct cxl_port *port = ep->uport;
+
+		p->ep_cxld[i] = cxl_pop_decoder(port);
+		if (IS_ERR(p->ep_cxld[i])) {
+			int err = PTR_ERR(p->ep_cxld[i]);
+
+			trace_cxl_region_decoder(region, port);
+			p->ep_cxld[i] = NULL;
+			put_all_decoders(p);
+			return err;
+		}
+	}
+
+	/* TODO: Switches */
+
+	for (i = 0; i < hb_count; i++) {
+		struct cxl_port *hb = hbs[i];
+
+		p->hbs[i].cxld = cxl_pop_decoder(hb);
+		if (IS_ERR(p->hbs[i].cxld)) {
+			int err = PTR_ERR(p->hbs[i].cxld);
+
+			trace_cxl_region_decoder(region, hb);
+			p->hbs[i].cxld = NULL;
+			put_all_decoders(p);
+			return err;
+		}
+	}
+
+	return devm_add_action_or_reset((struct device *)&region->dev,
+					release_decoders, p);
 }
 
 static int bind_region(const struct cxl_region *region)
@@ -516,7 +573,7 @@ static int cxl_region_probe(struct device *dev)
 	if (ours)
 		put_device(&ours->dev);
 
-	ret = gather_hdm_decoders(region);
+	ret = gather_hdm_decoders(region, &region->state);
 	if (ret)
 		return ret;
 
diff --git a/drivers/cxl/region.h b/drivers/cxl/region.h
index 51f442636364..4c0b94c3c001 100644
--- a/drivers/cxl/region.h
+++ b/drivers/cxl/region.h
@@ -23,6 +23,8 @@
  * @state.hbs: Host bridge state. One per hostbridge in the interleave set.
  * @state.hbs.rp_count: Count of root ports for this region
  * @state.hbs.rp_target_list: Ordered list of downstream root ports.
+ * @state.hbs.cxld: an available decoder to set up the programming.
+ * @state.ep_cxld: available decoders for endpoint programming.
  */
 struct cxl_region {
 	struct device dev;
@@ -44,7 +46,9 @@ struct cxl_region {
 		struct {
 			int rp_count;
 			struct cxl_dport *rp_target_list[CXL_DECODER_MAX_INTERLEAVE];
+			struct cxl_decoder *cxld;
 		} hbs[CXL_DECODER_MAX_INTERLEAVE];
+		struct cxl_decoder *ep_cxld[CXL_DECODER_MAX_INTERLEAVE];
 	} state;
 };
 
diff --git a/drivers/cxl/trace.h b/drivers/cxl/trace.h
index 57fe9342817c..516a7aed8a27 100644
--- a/drivers/cxl/trace.h
+++ b/drivers/cxl/trace.h
@@ -45,6 +45,27 @@ DEFINE_EVENT(cxl_region_template, hb_rp_valid,
 	     TP_PROTO(const struct cxl_region *region, char *status),
 	     TP_ARGS(region, status));
 
+TRACE_EVENT(cxl_region_decoder,
+	TP_PROTO(const struct cxl_region *region, struct cxl_port *port),
+
+	TP_ARGS(region, port),
+
+	TP_STRUCT__entry(
+		__field(const struct cxl_region *, region)
+		__field(struct cxl_port *, port)
+		__string(rdev_name, dev_name(&region->dev))
+		__string(pdev_name, dev_name(&port->dev))
+	),
+
+	TP_fast_assign(
+		__assign_str(rdev_name, dev_name(&region->dev));
+		__assign_str(pdev_name, dev_name(&port->dev));
+	),
+
+	TP_printk("%s: HDM decoder error for %s", __get_str(rdev_name), __get_str(pdev_name))
+);
+
+
 #endif /* if !defined (__CXL_TRACE_H__) || defined(TRACE_HEADER_MULTI_READ) */
 
 /* This part must be outside protection */
-- 
2.33.1