cxl/hdm: Enumerate allocated DPA

In preparation for provisioning CXL regions, add accounting for the DPA
space consumed by existing regions / decoders. Recall, a CXL region is a
memory range comprised from one or more endpoint devices contributing a
mapping of their DPA into HPA space through a decoder.

Record the DPA ranges covered by committed decoders at initial probe of
endpoint ports relative to a per-device resource tree of the DPA type
(pmem or volatile-ram).

The cxl_dpa_rwsem semaphore is introduced to globally synchronize DPA
state across all endpoints and their decoders at once. The vast majority
of DPA operations are reads as region creation is expected to be as rare
as disk partitioning and volume creation. The device_lock() for this
synchronization is specifically avoided for concern of entangling with
sysfs attribute removal.

Co-developed-by: Ben Widawsky <bwidawsk@kernel.org>
Signed-off-by: Ben Widawsky <bwidawsk@kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/165784327682.1758207.7914919426043855876.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

3 files changed, 149 insertions, 11 deletions

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index 650363d5272f..47e3af440b3d 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -153,10 +153,107 @@ void cxl_dpa_debug(struct seq_file *file, struct cxl_dev_state *cxlds)
 }
 EXPORT_SYMBOL_NS_GPL(cxl_dpa_debug, CXL);
 
+/*
+ * Must be called in a context that synchronizes against this decoder's
+ * port ->remove() callback (like an endpoint decoder sysfs attribute)
+ */
+static void __cxl_dpa_release(struct cxl_endpoint_decoder *cxled)
+{
+	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+	struct cxl_dev_state *cxlds = cxlmd->cxlds;
+	struct resource *res = cxled->dpa_res;
+	resource_size_t skip_start;
+
+	lockdep_assert_held_write(&cxl_dpa_rwsem);
+
+	/* save @skip_start, before @res is released */
+	skip_start = res->start - cxled->skip;
+	__release_region(&cxlds->dpa_res, res->start, resource_size(res));
+	if (cxled->skip)
+		__release_region(&cxlds->dpa_res, skip_start, cxled->skip);
+	cxled->skip = 0;
+	cxled->dpa_res = NULL;
+}
+
+static void cxl_dpa_release(void *cxled)
+{
+	down_write(&cxl_dpa_rwsem);
+	__cxl_dpa_release(cxled);
+	up_write(&cxl_dpa_rwsem);
+}
+
+static int __cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
+			     resource_size_t base, resource_size_t len,
+			     resource_size_t skipped)
+{
+	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+	struct cxl_port *port = cxled_to_port(cxled);
+	struct cxl_dev_state *cxlds = cxlmd->cxlds;
+	struct device *dev = &port->dev;
+	struct resource *res;
+
+	lockdep_assert_held_write(&cxl_dpa_rwsem);
+
+	if (!len)
+		return 0;
+
+	if (cxled->dpa_res) {
+		dev_dbg(dev, "decoder%d.%d: existing allocation %pr assigned\n",
+			port->id, cxled->cxld.id, cxled->dpa_res);
+		return -EBUSY;
+	}
+
+	if (skipped) {
+		res = __request_region(&cxlds->dpa_res, base - skipped, skipped,
+				       dev_name(&cxled->cxld.dev), 0);
+		if (!res) {
+			dev_dbg(dev,
+				"decoder%d.%d: failed to reserve skipped space\n",
+				port->id, cxled->cxld.id);
+			return -EBUSY;
+		}
+	}
+	res = __request_region(&cxlds->dpa_res, base, len,
+			       dev_name(&cxled->cxld.dev), 0);
+	if (!res) {
+		dev_dbg(dev, "decoder%d.%d: failed to reserve allocation\n",
+			port->id, cxled->cxld.id);
+		if (skipped)
+			__release_region(&cxlds->dpa_res, base - skipped,
+					 skipped);
+		return -EBUSY;
+	}
+	cxled->dpa_res = res;
+	cxled->skip = skipped;
+
+	return 0;
+}
+
+static int devm_cxl_dpa_reserve(struct cxl_endpoint_decoder *cxled,
+				resource_size_t base, resource_size_t len,
+				resource_size_t skipped)
+{
+	struct cxl_port *port = cxled_to_port(cxled);
+	int rc;
+
+	down_write(&cxl_dpa_rwsem);
+	rc = __cxl_dpa_reserve(cxled, base, len, skipped);
+	up_write(&cxl_dpa_rwsem);
+
+	if (rc)
+		return rc;
+
+	return devm_add_action_or_reset(&port->dev, cxl_dpa_release, cxled);
+}
+
 static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
-			    int *target_map, void __iomem *hdm, int which)
+			    int *target_map, void __iomem *hdm, int which,
+			    u64 *dpa_base)
 {
-	u64 size, base;
+	struct cxl_endpoint_decoder *cxled = NULL;
+	u64 size, base, skip, dpa_size;
+	bool committed;
+	u32 remainder;
 	int i, rc;
 	u32 ctrl;
 	union {
@@ -164,11 +261,15 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
 		unsigned char target_id[8];
 	} target_list;
 
+	if (is_endpoint_decoder(&cxld->dev))
+		cxled = to_cxl_endpoint_decoder(&cxld->dev);
+
 	ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(which));
 	base = ioread64_hi_lo(hdm + CXL_HDM_DECODER0_BASE_LOW_OFFSET(which));
 	size = ioread64_hi_lo(hdm + CXL_HDM_DECODER0_SIZE_LOW_OFFSET(which));
+	committed = !!(ctrl & CXL_HDM_DECODER0_CTRL_COMMITTED);
 
-	if (!(ctrl & CXL_HDM_DECODER0_CTRL_COMMITTED))
+	if (!committed)
 		size = 0;
 	if (base == U64_MAX || size == U64_MAX) {
 		dev_warn(&port->dev, "decoder%d.%d: Invalid resource range\n",
@@ -181,8 +282,8 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
 		.end = base + size - 1,
 	};
 
-	/* switch decoders are always enabled if committed */
-	if (ctrl & CXL_HDM_DECODER0_CTRL_COMMITTED) {
+	/* decoders are enabled if committed */
+	if (committed) {
 		cxld->flags |= CXL_DECODER_F_ENABLE;
 		if (ctrl & CXL_HDM_DECODER0_CTRL_LOCK)
 			cxld->flags |= CXL_DECODER_F_LOCK;
@@ -211,14 +312,35 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
 	if (rc)
 		return rc;
 
-	if (is_endpoint_decoder(&cxld->dev))
+	if (!cxled) {
+		target_list.value =
+			ioread64_hi_lo(hdm + CXL_HDM_DECODER0_TL_LOW(which));
+		for (i = 0; i < cxld->interleave_ways; i++)
+			target_map[i] = target_list.target_id[i];
+
 		return 0;
+	}
 
-	target_list.value =
-		ioread64_hi_lo(hdm + CXL_HDM_DECODER0_TL_LOW(which));
-	for (i = 0; i < cxld->interleave_ways; i++)
-		target_map[i] = target_list.target_id[i];
+	if (!committed)
+		return 0;
 
+	dpa_size = div_u64_rem(size, cxld->interleave_ways, &remainder);
+	if (remainder) {
+		dev_err(&port->dev,
+			"decoder%d.%d: invalid committed configuration size: %#llx ways: %d\n",
+			port->id, cxld->id, size, cxld->interleave_ways);
+		return -ENXIO;
+	}
+	skip = ioread64_hi_lo(hdm + CXL_HDM_DECODER0_SKIP_LOW(which));
+	rc = devm_cxl_dpa_reserve(cxled, *dpa_base + skip, dpa_size, skip);
+	if (rc) {
+		dev_err(&port->dev,
+			"decoder%d.%d: Failed to reserve DPA range %#llx - %#llx\n (%d)",
+			port->id, cxld->id, *dpa_base,
+			*dpa_base + dpa_size + skip - 1, rc);
+		return rc;
+	}
+	*dpa_base += dpa_size + skip;
 	return 0;
 }
 
@@ -231,6 +353,7 @@ int devm_cxl_enumerate_decoders(struct cxl_hdm *cxlhdm)
 	void __iomem *hdm = cxlhdm->regs.hdm_decoder;
 	struct cxl_port *port = cxlhdm->port;
 	int i, committed;
+	u64 dpa_base = 0;
 	u32 ctrl;
 
 	/*
@@ -277,7 +400,7 @@ int devm_cxl_enumerate_decoders(struct cxl_hdm *cxlhdm)
 			cxld = &cxlsd->cxld;
 		}
 
-		rc = init_hdm_decoder(port, cxld, target_map, hdm, i);
+		rc = init_hdm_decoder(port, cxld, target_map, hdm, i, &dpa_base);
 		if (rc) {
 			put_device(&cxld->dev);
 			return rc;
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index e0b1e2e4dfee..5fe8b59a0b18 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -56,6 +56,8 @@
 #define   CXL_HDM_DECODER0_CTRL_TYPE BIT(12)
 #define CXL_HDM_DECODER0_TL_LOW(i) (0x20 * (i) + 0x24)
 #define CXL_HDM_DECODER0_TL_HIGH(i) (0x20 * (i) + 0x28)
+#define CXL_HDM_DECODER0_SKIP_LOW(i) CXL_HDM_DECODER0_TL_LOW(i)
+#define CXL_HDM_DECODER0_SKIP_HIGH(i) CXL_HDM_DECODER0_TL_HIGH(i)
 
 static inline int cxl_hdm_decoder_count(u32 cap_hdr)
 {
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index bfa2eaf649a9..ed731124fa10 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -50,6 +50,19 @@ static inline struct cxl_memdev *to_cxl_memdev(struct device *dev)
 	return container_of(dev, struct cxl_memdev, dev);
 }
 
+static inline struct cxl_port *cxled_to_port(struct cxl_endpoint_decoder *cxled)
+{
+	return to_cxl_port(cxled->cxld.dev.parent);
+}
+
+static inline struct cxl_memdev *
+cxled_to_memdev(struct cxl_endpoint_decoder *cxled)
+{
+	struct cxl_port *port = to_cxl_port(cxled->cxld.dev.parent);
+
+	return to_cxl_memdev(port->uport);
+}
+
 bool is_cxl_memdev(struct device *dev);
 static inline bool is_cxl_endpoint(struct cxl_port *port)
 {