1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Copyright(c) 2022 Intel Corporation. All rights reserved. */
3 #include <linux/debugfs.h>
4 #include <linux/device.h>
5 #include <linux/module.h>
6 #include <linux/pci.h>
7
8 #include "cxlmem.h"
9 #include "cxlpci.h"
10
11 /**
12 * DOC: cxl mem
13 *
14 * CXL memory endpoint devices and switches are CXL capable devices that are
15 * participating in CXL.mem protocol. Their functionality builds on top of the
16 * CXL.io protocol that allows enumerating and configuring components via
17 * standard PCI mechanisms.
18 *
19 * The cxl_mem driver owns kicking off the enumeration of this CXL.mem
20 * capability. With the detection of a CXL capable endpoint, the driver will
21 * walk up to find the platform specific port it is connected to, and determine
22 * if there are intervening switches in the path. If there are switches, a
23 * secondary action is to enumerate those (implemented in cxl_core). Finally the
24 * cxl_mem driver adds the device it is bound to as a CXL endpoint-port for use
25 * in higher level operations.
26 */
27
enable_suspend(void * data)28 static void enable_suspend(void *data)
29 {
30 cxl_mem_active_dec();
31 }
32
remove_debugfs(void * dentry)33 static void remove_debugfs(void *dentry)
34 {
35 debugfs_remove_recursive(dentry);
36 }
37
cxl_mem_dpa_show(struct seq_file * file,void * data)38 static int cxl_mem_dpa_show(struct seq_file *file, void *data)
39 {
40 struct device *dev = file->private;
41 struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
42
43 cxl_dpa_debug(file, cxlmd->cxlds);
44
45 return 0;
46 }
47
cxl_mem_probe(struct device * dev)48 static int cxl_mem_probe(struct device *dev)
49 {
50 struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
51 struct cxl_port *parent_port;
52 struct cxl_dport *dport;
53 struct dentry *dentry;
54 int rc;
55
56 /*
57 * Someone is trying to reattach this device after it lost its port
58 * connection (an endpoint port previously registered by this memdev was
59 * disabled). This racy check is ok because if the port is still gone,
60 * no harm done, and if the port hierarchy comes back it will re-trigger
61 * this probe. Port rescan and memdev detach work share the same
62 * single-threaded workqueue.
63 */
64 if (work_pending(&cxlmd->detach_work))
65 return -EBUSY;
66
67 dentry = cxl_debugfs_create_dir(dev_name(dev));
68 debugfs_create_devm_seqfile(dev, "dpamem", dentry, cxl_mem_dpa_show);
69 rc = devm_add_action_or_reset(dev, remove_debugfs, dentry);
70 if (rc)
71 return rc;
72
73 rc = devm_cxl_enumerate_ports(cxlmd);
74 if (rc)
75 return rc;
76
77 parent_port = cxl_mem_find_port(cxlmd, &dport);
78 if (!parent_port) {
79 dev_err(dev, "CXL port topology not found\n");
80 return -ENXIO;
81 }
82
83 device_lock(&parent_port->dev);
84 if (!parent_port->dev.driver) {
85 dev_err(dev, "CXL port topology %s not enabled\n",
86 dev_name(&parent_port->dev));
87 rc = -ENXIO;
88 goto unlock;
89 }
90
91 rc = devm_cxl_add_endpoint(cxlmd, dport);
92 unlock:
93 device_unlock(&parent_port->dev);
94 put_device(&parent_port->dev);
95 if (rc)
96 return rc;
97
98 /*
99 * The kernel may be operating out of CXL memory on this device,
100 * there is no spec defined way to determine whether this device
101 * preserves contents over suspend, and there is no simple way
102 * to arrange for the suspend image to avoid CXL memory which
103 * would setup a circular dependency between PCI resume and save
104 * state restoration.
105 *
106 * TODO: support suspend when all the regions this device is
107 * hosting are locked and covered by the system address map,
108 * i.e. platform firmware owns restoring the HDM configuration
109 * that it locked.
110 */
111 cxl_mem_active_inc();
112 return devm_add_action_or_reset(dev, enable_suspend, NULL);
113 }
114
115 static struct cxl_driver cxl_mem_driver = {
116 .name = "cxl_mem",
117 .probe = cxl_mem_probe,
118 .id = CXL_DEVICE_MEMORY_EXPANDER,
119 };
120
121 module_cxl_driver(cxl_mem_driver);
122
123 MODULE_LICENSE("GPL v2");
124 MODULE_IMPORT_NS(CXL);
125 MODULE_ALIAS_CXL(CXL_DEVICE_MEMORY_EXPANDER);
126 /*
127 * create_endpoint() wants to validate port driver attach immediately after
128 * endpoint registration.
129 */
130 MODULE_SOFTDEP("pre: cxl_port");
131
