cxl: Remove core/acpi.c and cxl core dependency on ACPI

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/20250610172938.139428-1-dave.jiang@intel.com

[ dj: Remove core/acpi.o from tools/testing/cxl/Kbuild ]
[ dj: Add kdoc for cxlrd->cache_size ]

Cc: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Robert Richter <rrichter@amd.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20250711151529.787470-1-rrichter@amd.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

4 files changed, 1 insertions, 20 deletions

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;