Subject: [PATCH v2] cxl: Remove core/acpi.c and cxl core dependency on ACPI

From: Robert Richter <[email-masked]>
Date: Tue, 15 Jul 2025 12:40:16 +0200

>From Dave [1]:

"""
It was a mistake to introduce core/acpi.c and putting ACPI dependency on
cxl_core when adding the extended linear cache support.
"""

Current implementation calls hmat_get_extended_linear_cache_size() of
the ACPI subsystem. That external reference causes issue running
cxl_test as there is no way to "mock" that function and ignore it when
using cxl test.

Instead of working around that using cxlrd ops and extensively
expanding cxl_test code [1], just move HMAT calls out of the core
module to cxl_acpi. Implement this by adding a @cache_size member to
struct cxl_root_decoder. During initialization the cache size is
determined and added to the root decoder object in cxl_acpi. Later on
in cxl_core the cache_size parameter is used to setup extended linear
caching.

[1] https://patch.msgid.link/[email-masked]

[ dj: Remove core/acpi.o from tools/testing/cxl/Kbuild ]

Cc: Dave Jiang <[email-masked]>
Signed-off-by: Robert Richter <[email-masked]>
Reviewed-by: Alison Schofield <[email-masked]>
Reviewed-by: Jonathan Cameron <[email-masked]>
Reviewed-by: Dave Jiang <[email-masked]>
Link: https://patch.msgid.link/[email-masked]
Signed-off-by: Dave Jiang <[email-masked]>
Signed-off-by: Robert Richter <[email-masked]>
---
v2:
 * fixed linux-next build error (htmldocs)
---
 drivers/cxl/acpi.c        | 59 +++++++++++++++++++++++++++++++++++++++
 drivers/cxl/core/Makefile |  1 -
 drivers/cxl/core/acpi.c   | 11 --------
 drivers/cxl/core/core.h   |  2 --
 drivers/cxl/core/region.c |  7 +----
 drivers/cxl/cxl.h         |  2 ++
 tools/testing/cxl/Kbuild  |  1 -
 7 files changed, 62 insertions(+), 21 deletions(-)
 delete mode 100644 drivers/cxl/core/acpi.c

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index a1a99ec3f12c..712624cba2b6 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -335,6 +335,63 @@ static int add_or_reset_cxl_resource(struct resource *parent, struct resource *r
 	return rc;
 }
 
+static int cxl_acpi_set_cache_size(struct cxl_root_decoder *cxlrd)
+{
+	struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
+	struct range *hpa = &cxld->hpa_range;
+	resource_size_t size = range_len(hpa);
+	resource_size_t start = hpa->start;
+	resource_size_t cache_size;
+	struct resource res;
+	int nid, rc;
+
+	res = DEFINE_RES(start, size, 0);
+	nid = phys_to_target_node(start);
+
+	rc = hmat_get_extended_linear_cache_size(&res, nid, &cache_size);
+	if (rc)
+		return rc;
+
+	/*
+	 * The cache range is expected to be within the CFMWS.
+	 * Currently there is only support cache_size == cxl_size. CXL
+	 * size is then half of the total CFMWS window size.
+	 */
+	size = size >> 1;
+	if (cache_size && size != cache_size) {
+		dev_warn(&cxld->dev,
+			 "Extended Linear Cache size %pa != CXL size %pa. No Support!",
+			 &cache_size, &size);
+		return -ENXIO;
+	}
+
+	cxlrd->cache_size = cache_size;
+
+	return 0;
+}
+
+static void cxl_setup_extended_linear_cache(struct cxl_root_decoder *cxlrd)
+{
+	int rc;
+
+	rc = cxl_acpi_set_cache_size(cxlrd);
+	if (!rc)
+		return;
+
+	if (rc != -EOPNOTSUPP) {
+		/*
+		 * Failing to support extended linear cache region resize does not
+		 * prevent the region from functioning. Only causes cxl list showing
+		 * incorrect region size.
+		 */
+		dev_warn(cxlrd->cxlsd.cxld.dev.parent,
+			 "Extended linear cache calculation failed rc:%d\n", rc);
+	}
+
+	/* Ignoring return code */
+	cxlrd->cache_size = 0;
+}
+
 DEFINE_FREE(put_cxlrd, struct cxl_root_decoder *,
 	    if (!IS_ERR_OR_NULL(_T)) put_device(&_T->cxlsd.cxld.dev))
 DEFINE_FREE(del_cxl_resource, struct resource *, if (_T) del_cxl_resource(_T))
@@ -394,6 +451,8 @@ static int __cxl_parse_cfmws(struct acpi_cedt_cfmws *cfmws,
 		ig = CXL_DECODER_MIN_GRANULARITY;
 	cxld->interleave_granularity = ig;
 
+	cxl_setup_extended_linear_cache(cxlrd);
+
 	if (cfmws->interleave_arithmetic == ACPI_CEDT_CFMWS_ARITHMETIC_XOR) {
 		if (ways != 1 && ways != 3) {
 			cxims_ctx = (struct cxl_cxims_context) {
diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
index 79e2ef81fde8..5ad8fef210b5 100644
--- a/drivers/cxl/core/Makefile
+++ b/drivers/cxl/core/Makefile
@@ -15,7 +15,6 @@ cxl_core-y += hdm.o
 cxl_core-y += pmu.o
 cxl_core-y += cdat.o
 cxl_core-y += ras.o
-cxl_core-y += acpi.o
 cxl_core-$(CONFIG_TRACING) += trace.o
 cxl_core-$(CONFIG_CXL_REGION) += region.o
 cxl_core-$(CONFIG_CXL_MCE) += mce.o
diff --git a/drivers/cxl/core/acpi.c b/drivers/cxl/core/acpi.c
deleted file mode 100644
index f13b4dae6ac5..000000000000
--- a/drivers/cxl/core/acpi.c
+++ /dev/null
@@ -1,11 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/* Copyright(c) 2024 Intel Corporation. All rights reserved. */
-#include <linux/acpi.h>
-#include "cxl.h"
-#include "core.h"
-
-int cxl_acpi_get_extended_linear_cache_size(struct resource *backing_res,
-					    int nid, resource_size_t *size)
-{
-	return hmat_get_extended_linear_cache_size(backing_res, nid, size);
-}
diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 6b78b10da3e1..2250c05cecc3 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -121,8 +121,6 @@ int cxl_port_get_switch_dport_bandwidth(struct cxl_port *port,
 int cxl_ras_init(void);
 void cxl_ras_exit(void);
 int cxl_gpf_port_setup(struct cxl_dport *dport);
-int cxl_acpi_get_extended_linear_cache_size(struct resource *backing_res,
-					    int nid, resource_size_t *size);
 
 #ifdef CONFIG_CXL_FEATURES
 struct cxl_feat_entry *
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 91ff3a495fbd..08ac7f483562 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3282,15 +3282,10 @@ static int cxl_extended_linear_cache_resize(struct cxl_region *cxlr,
 {
 	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
 	struct cxl_region_params *p = &cxlr->params;
-	int nid = phys_to_target_node(res->start);
 	resource_size_t size = resource_size(res);
 	resource_size_t cache_size, start;
-	int rc;
-
-	rc = cxl_acpi_get_extended_linear_cache_size(res, nid, &cache_size);
-	if (rc)
-		return rc;
 
+	cache_size = cxlrd->cache_size;
 	if (!cache_size)
 		return 0;
 
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index e7b66ca1d423..b3aab7c7d17f 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -423,6 +423,7 @@ typedef u64 (*cxl_hpa_to_spa_fn)(struct cxl_root_decoder *cxlrd, u64 hpa);
 /**
  * struct cxl_root_decoder - Static platform CXL address decoder
  * @res: host / parent resource for region allocations
+ * @cache_size: extended linear cache size if exists, otherwise zero
  * @region_id: region id for next region provisioning event
  * @hpa_to_spa: translate CXL host-physical-address to Platform system-physical-address
  * @platform_data: platform specific configuration data
@@ -432,6 +433,7 @@ typedef u64 (*cxl_hpa_to_spa_fn)(struct cxl_root_decoder *cxlrd, u64 hpa);
  */
 struct cxl_root_decoder {
 	struct resource *res;
+	resource_size_t cache_size;
 	atomic_t region_id;
 	cxl_hpa_to_spa_fn hpa_to_spa;
 	void *platform_data;
diff --git a/tools/testing/cxl/Kbuild b/tools/testing/cxl/Kbuild
index 31a2d73c963f..d07f14cb7aa4 100644
--- a/tools/testing/cxl/Kbuild
+++ b/tools/testing/cxl/Kbuild
@@ -62,7 +62,6 @@ cxl_core-y += $(CXL_CORE_SRC)/hdm.o
 cxl_core-y += $(CXL_CORE_SRC)/pmu.o
 cxl_core-y += $(CXL_CORE_SRC)/cdat.o
 cxl_core-y += $(CXL_CORE_SRC)/ras.o
-cxl_core-y += $(CXL_CORE_SRC)/acpi.o
 cxl_core-$(CONFIG_TRACING) += $(CXL_CORE_SRC)/trace.o
 cxl_core-$(CONFIG_CXL_REGION) += $(CXL_CORE_SRC)/region.o
 cxl_core-$(CONFIG_CXL_MCE) += $(CXL_CORE_SRC)/mce.o
-- 
2.39.5