netdev - [PATCH v22 11/25] cxl/hdm: Add support for getting region from committed decoder

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Message-ID: <20251205115248.772945-12-alejandro.lucero-palau@amd.com>
Date: Fri, 5 Dec 2025 11:52:34 +0000
From: <alejandro.lucero-palau@....com>
To: <linux-cxl@...r.kernel.org>, <netdev@...r.kernel.org>,
	<dan.j.williams@...el.com>, <edward.cree@....com>, <davem@...emloft.net>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <edumazet@...gle.com>,
	<dave.jiang@...el.com>
CC: Alejandro Lucero <alucerop@....com>
Subject: [PATCH v22 11/25]  cxl/hdm: Add support for getting region from committed decoder

From: Alejandro Lucero <alucerop@....com>

A Type2 device configured by the BIOS can already have its HDM
committed. Add a cxl_get_committed_decoder() function for cheking
so after memdev creation. A CXL region should have been created
during memdev initialization, therefore a Type2 driver can ask for
such a region for working with the HPA. If the HDM is not committed,
a Type2 driver will create the region after obtaining proper HPA
and DPA space.

Signed-off-by: Alejandro Lucero <alucerop@....com>
---
 drivers/cxl/core/hdm.c | 44 ++++++++++++++++++++++++++++++++++++++++++
 include/cxl/cxl.h      |  3 +++
 2 files changed, 47 insertions(+)

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index d3a094ca01ad..fa99657440d1 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -92,6 +92,7 @@ static void parse_hdm_decoder_caps(struct cxl_hdm *cxlhdm)
 static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
 {
 	struct cxl_hdm *cxlhdm;
+	struct cxl_port *port;
 	void __iomem *hdm;
 	u32 ctrl;
 	int i;
@@ -105,6 +106,10 @@ static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
 	if (!hdm)
 		return true;
 
+	port = cxlhdm->port;
+	if (is_cxl_endpoint(port))
+		return false;
+
 	/*
 	 * If HDM decoders are present and the driver is in control of
 	 * Mem_Enable skip DVSEC based emulation
@@ -686,6 +691,45 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, u64 size)
 	return devm_add_action_or_reset(&port->dev, cxl_dpa_release, cxled);
 }
 
+static int find_committed_decoder(struct device *dev, const void *data)
+{
+	struct cxl_endpoint_decoder *cxled;
+	struct cxl_port *port;
+
+	if (!is_endpoint_decoder(dev))
+		return 0;
+
+	cxled = to_cxl_endpoint_decoder(dev);
+	port = cxled_to_port(cxled);
+
+	return cxled->cxld.id == (port->hdm_end);
+}
+
+struct cxl_endpoint_decoder *cxl_get_committed_decoder(struct cxl_memdev *cxlmd,
+						       struct cxl_region **cxlr)
+{
+	struct cxl_port *endpoint = cxlmd->endpoint;
+	struct cxl_endpoint_decoder *cxled;
+	struct device *cxled_dev;
+
+	if (!endpoint)
+		return NULL;
+
+	guard(rwsem_read)(&cxl_rwsem.dpa);
+	cxled_dev = device_find_child(&endpoint->dev, NULL,
+				      find_committed_decoder);
+
+	if (!cxled_dev)
+		return NULL;
+
+	cxled = to_cxl_endpoint_decoder(cxled_dev);
+	*cxlr = cxled->cxld.region;
+
+	put_device(cxled_dev);
+	return cxled;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_get_committed_decoder, "CXL");
+
 static void cxld_set_interleave(struct cxl_decoder *cxld, u32 *ctrl)
 {
 	u16 eig;
diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
index 043fc31c764e..2ff3c19c684c 100644
--- a/include/cxl/cxl.h
+++ b/include/cxl/cxl.h
@@ -250,4 +250,7 @@ int cxl_set_capacity(struct cxl_dev_state *cxlds, u64 capacity);
 struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
 				       struct cxl_dev_state *cxlds,
 				       const struct cxl_memdev_ops *ops);
+struct cxl_region;
+struct cxl_endpoint_decoder *cxl_get_committed_decoder(struct cxl_memdev *cxlmd,
+						       struct cxl_region **cxlr);
 #endif /* __CXL_CXL_H__ */
-- 
2.34.1