tools/testing/cxl: Introduce a mock memory device + driver

Introduce an emulated device-set plus driver to register CXL memory
devices, 'struct cxl_memdev' instances, in the mock cxl_test topology.
This enables the development of HDM Decoder (Host-managed Device Memory
Decoder) programming flow (region provisioning) in an environment that
can be updated alongside the kernel as it gains more functionality.

Whereas the cxl_pci module looks for CXL memory expanders on the 'pci'
bus, the cxl_mock_mem module attaches to CXL expanders on the platform
bus emitted by cxl_test.

Acked-by: Ben Widawsky <ben.widawsky@intel.com>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/163116440099.2460985.10692549614409346604.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/pmem.c

@@ -51,16 +51,16 @@ struct cxl_nvdimm_bridge *to_cxl_nvdimm_bridge(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(to_cxl_nvdimm_bridge);
 
-static int match_nvdimm_bridge(struct device *dev, const void *data)
+__mock int match_nvdimm_bridge(struct device *dev, const void *data)
 {
 	return dev->type == &cxl_nvdimm_bridge_type;
 }
 
-struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(void)
+struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_nvdimm *cxl_nvd)
 {
 	struct device *dev;
 
-	dev = bus_find_device(&cxl_bus_type, NULL, NULL, match_nvdimm_bridge);
+	dev = bus_find_device(&cxl_bus_type, NULL, cxl_nvd, match_nvdimm_bridge);
 	if (!dev)
 		return NULL;
 	return to_cxl_nvdimm_bridge(dev);

drivers/cxl/cxl.h

@@ -327,7 +327,7 @@ struct cxl_nvdimm_bridge *devm_cxl_add_nvdimm_bridge(struct device *host,
 struct cxl_nvdimm *to_cxl_nvdimm(struct device *dev);
 bool is_cxl_nvdimm(struct device *dev);
 int devm_cxl_add_nvdimm(struct device *host, struct cxl_memdev *cxlmd);
-struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(void);
+struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_nvdimm *cxl_nvd);
 
 /*
  * Unit test builds overrides this to __weak, find the 'strong' version

drivers/cxl/pmem.c

@@ -39,7 +39,7 @@ static int cxl_nvdimm_probe(struct device *dev)
 	struct nvdimm *nvdimm;
 	int rc;
 
-	cxl_nvb = cxl_find_nvdimm_bridge();
+	cxl_nvb = cxl_find_nvdimm_bridge(cxl_nvd);
 	if (!cxl_nvb)
 		return -ENXIO;
 

tools/testing/cxl/Kbuild

@@ -33,4 +33,6 @@ cxl_core-y += $(CXL_CORE_SRC)/memdev.o
 cxl_core-y += $(CXL_CORE_SRC)/mbox.o
 cxl_core-y += config_check.o
 
+cxl_core-y += mock_pmem.o
+
 obj-m += test/

tools/testing/cxl/mock_pmem.c

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2021 Intel Corporation. All rights reserved. */
+#include <cxl.h>
+#include "test/mock.h"
+#include <core/core.h>
+
+int match_nvdimm_bridge(struct device *dev, const void *data)
+{
+	int index, rc = 0;
+	struct cxl_mock_ops *ops = get_cxl_mock_ops(&index);
+	const struct cxl_nvdimm *cxl_nvd = data;
+
+	if (ops) {
+		if (dev->type == &cxl_nvdimm_bridge_type &&
+		    (ops->is_mock_dev(dev->parent->parent) ==
+		     ops->is_mock_dev(cxl_nvd->dev.parent->parent)))
+			rc = 1;
+	} else
+		rc = dev->type == &cxl_nvdimm_bridge_type;
+
+	put_cxl_mock_ops(index);
+
+	return rc;
+}

tools/testing/cxl/test/Kbuild

@@ -1,6 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
+ccflags-y := -I$(srctree)/drivers/cxl/
+
 obj-m += cxl_test.o
 obj-m += cxl_mock.o
+obj-m += cxl_mock_mem.o
 
 cxl_test-y := cxl.o
 cxl_mock-y := mock.o
+cxl_mock_mem-y := mem.o

tools/testing/cxl/test/cxl.c

@@ -17,6 +17,7 @@ static struct platform_device *cxl_acpi;
 static struct platform_device *cxl_host_bridge[NR_CXL_HOST_BRIDGES];
 static struct platform_device
 	*cxl_root_port[NR_CXL_HOST_BRIDGES * NR_CXL_ROOT_PORTS];
+struct platform_device *cxl_mem[NR_CXL_HOST_BRIDGES * NR_CXL_ROOT_PORTS];
 
 static struct acpi_device acpi0017_mock;
 static struct acpi_device host_bridge[NR_CXL_HOST_BRIDGES] = {
@@ -36,6 +37,11 @@ static struct acpi_device host_bridge[NR_CXL_HOST_BRIDGES] = {
 
 static bool is_mock_dev(struct device *dev)
 {
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(cxl_mem); i++)
+		if (dev == &cxl_mem[i]->dev)
+			return true;
 	if (dev == &cxl_acpi->dev)
 		return true;
 	return false;
@@ -405,6 +411,44 @@ static void mock_companion(struct acpi_device *adev, struct device *dev)
 #define SZ_512G (SZ_64G * 8)
 #endif
 
+static struct platform_device *alloc_memdev(int id)
+{
+	struct resource res[] = {
+		[0] = {
+			.flags = IORESOURCE_MEM,
+		},
+		[1] = {
+			.flags = IORESOURCE_MEM,
+			.desc = IORES_DESC_PERSISTENT_MEMORY,
+		},
+	};
+	struct platform_device *pdev;
+	int i, rc;
+
+	for (i = 0; i < ARRAY_SIZE(res); i++) {
+		struct cxl_mock_res *r = alloc_mock_res(SZ_256M);
+
+		if (!r)
+			return NULL;
+		res[i].start = r->range.start;
+		res[i].end = r->range.end;
+	}
+
+	pdev = platform_device_alloc("cxl_mem", id);
+	if (!pdev)
+		return NULL;
+
+	rc = platform_device_add_resources(pdev, res, ARRAY_SIZE(res));
+	if (rc)
+		goto err;
+
+	return pdev;
+
+err:
+	platform_device_put(pdev);
+	return NULL;
+}
+
 static __init int cxl_test_init(void)
 {
 	int rc, i;
@@ -460,9 +504,27 @@ static __init int cxl_test_init(void)
 		cxl_root_port[i] = pdev;
 	}
 
+	BUILD_BUG_ON(ARRAY_SIZE(cxl_mem) != ARRAY_SIZE(cxl_root_port));
+	for (i = 0; i < ARRAY_SIZE(cxl_mem); i++) {
+		struct platform_device *port = cxl_root_port[i];
+		struct platform_device *pdev;
+
+		pdev = alloc_memdev(i);
+		if (!pdev)
+			goto err_mem;
+		pdev->dev.parent = &port->dev;
+
+		rc = platform_device_add(pdev);
+		if (rc) {
+			platform_device_put(pdev);
+			goto err_mem;
+		}
+		cxl_mem[i] = pdev;
+	}
+
 	cxl_acpi = platform_device_alloc("cxl_acpi", 0);
 	if (!cxl_acpi)
-		goto err_port;
+		goto err_mem;
 
 	mock_companion(&acpi0017_mock, &cxl_acpi->dev);
 	acpi0017_mock.dev.bus = &platform_bus_type;
@@ -475,6 +537,9 @@ static __init int cxl_test_init(void)
 
 err_add:
 	platform_device_put(cxl_acpi);
+err_mem:
+	for (i = ARRAY_SIZE(cxl_mem) - 1; i >= 0; i--)
+		platform_device_unregister(cxl_mem[i]);
 err_port:
 	for (i = ARRAY_SIZE(cxl_root_port) - 1; i >= 0; i--)
 		platform_device_unregister(cxl_root_port[i]);
@@ -495,6 +560,8 @@ static __exit void cxl_test_exit(void)
 	int i;
 
 	platform_device_unregister(cxl_acpi);
+	for (i = ARRAY_SIZE(cxl_mem) - 1; i >= 0; i--)
+		platform_device_unregister(cxl_mem[i]);
 	for (i = ARRAY_SIZE(cxl_root_port) - 1; i >= 0; i--)
 		platform_device_unregister(cxl_root_port[i]);
 	for (i = ARRAY_SIZE(cxl_host_bridge) - 1; i >= 0; i--)