powerpc/powernv: Move core and fadump_release_opalcore under new kobject

The /sys/firmware/opal/core and /sys/kernel/fadump_release_opalcore
sysfs files are used to export and release the OPAL memory on PowerNV
platform. let's organize them into a new kobject under
/sys/firmware/opal/mpipl/ directory.

A symlink is added to maintain the backward compatibility for
/sys/firmware/opal/core sysfs file.

Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191211160910.21656-5-sourabhjain@linux.ibm.com

Documentation/ABI/removed/sysfs-kernel-fadump_release_opalcore

@@ -1,3 +1,5 @@
+This ABI is moved to /sys/firmware/opal/mpipl/release_core.
+
 What:		/sys/kernel/fadump_release_opalcore
 Date:		Sep 2019
 Contact:	linuxppc-dev@lists.ozlabs.org

Documentation/powerpc/firmware-assisted-dump.rst

@@ -112,13 +112,13 @@ to ensure that crash data is preserved to process later.
 
 -- On OPAL based machines (PowerNV), if the kernel is build with
    CONFIG_OPAL_CORE=y, OPAL memory at the time of crash is also
-   exported as /sys/firmware/opal/core file. This procfs file is
+   exported as /sys/firmware/opal/mpipl/core file. This procfs file is
    helpful in debugging OPAL crashes with GDB. The kernel memory
    used for exporting this procfs file can be released by echo'ing
-   '1' to /sys/kernel/fadump_release_opalcore node.
+   '1' to /sys/firmware/opal/mpipl/release_core node.
 
    e.g.
-     # echo 1 > /sys/kernel/fadump_release_opalcore
+     # echo 1 > /sys/firmware/opal/mpipl/release_core
 
 Implementation details:
 -----------------------
@@ -283,14 +283,17 @@ Here is the list of files under kernel sysfs:
     enhanced to use this interface to release the memory reserved for
     dump and continue without 2nd reboot.
 
- /sys/kernel/fadump_release_opalcore
+Note: /sys/kernel/fadump_release_opalcore sysfs has moved to
+      /sys/firmware/opal/mpipl/release_core
+
+ /sys/firmware/opal/mpipl/release_core
 
     This file is available only on OPAL based machines when FADump is
     active during capture kernel. This is used to release the memory
-    used by the kernel to export /sys/firmware/opal/core file. To
+    used by the kernel to export /sys/firmware/opal/mpipl/core file. To
     release this memory, echo '1' to it:
 
-    echo 1  > /sys/kernel/fadump_release_opalcore
+    echo 1  > /sys/firmware/opal/mpipl/release_core
 
 Here is the list of files under powerpc debugfs:
 (Assuming debugfs is mounted on /sys/kernel/debug directory.)

arch/powerpc/platforms/powernv/opal-core.c

@@ -71,6 +71,7 @@ static LIST_HEAD(opalcore_list);
 static struct opalcore_config *oc_conf;
 static const struct opal_mpipl_fadump *opalc_metadata;
 static const struct opal_mpipl_fadump *opalc_cpu_metadata;
+struct kobject *mpipl_kobj;
 
 /*
  * Set crashing CPU's signal to SIGUSR1. if the kernel is triggered
@@ -428,7 +429,7 @@ static void opalcore_cleanup(void)
 		return;
 
 	/* Remove OPAL core sysfs file */
-	sysfs_remove_bin_file(opal_kobj, &opal_core_attr);
+	sysfs_remove_bin_file(mpipl_kobj, &opal_core_attr);
 	oc_conf->ptload_phdr = NULL;
 	oc_conf->ptload_cnt = 0;
 
@@ -563,9 +564,9 @@ error_out:
 	of_node_put(np);
 }
 
-static ssize_t fadump_release_opalcore_store(struct kobject *kobj,
+static ssize_t release_core_store(struct kobject *kobj,
-					     struct kobj_attribute *attr,
+				  struct kobj_attribute *attr,
-					     const char *buf, size_t count)
+				  const char *buf, size_t count)
 {
 	int input = -1;
 
@@ -589,9 +590,23 @@ static ssize_t fadump_release_opalcore_store(struct kobject *kobj,
 	return count;
 }
 
-static struct kobj_attribute opalcore_rel_attr = __ATTR(fadump_release_opalcore,
+static struct kobj_attribute opalcore_rel_attr = __ATTR_WO(release_core);
-						0200, NULL,
+
-						fadump_release_opalcore_store);
+static struct attribute *mpipl_attr[] = {
+	&opalcore_rel_attr.attr,
+	NULL,
+};
+
+static struct bin_attribute *mpipl_bin_attr[] = {
+	&opal_core_attr,
+	NULL,
+
+};
+
+static struct attribute_group mpipl_group = {
+	.attrs = mpipl_attr,
+	.bin_attrs =  mpipl_bin_attr,
+};
 
 static int __init opalcore_init(void)
 {
@@ -609,7 +624,7 @@ static int __init opalcore_init(void)
 	 * then capture the dump.
 	 */
 	if (!(is_opalcore_usable())) {
-		pr_err("Failed to export /sys/firmware/opal/core\n");
+		pr_err("Failed to export /sys/firmware/opal/mpipl/core\n");
 		opalcore_cleanup();
 		return rc;
 	}
@@ -617,18 +632,28 @@ static int __init opalcore_init(void)
 	/* Set OPAL core file size */
 	opal_core_attr.size = oc_conf->opalcore_size;
 
+	mpipl_kobj = kobject_create_and_add("mpipl", opal_kobj);
+	if (!mpipl_kobj) {
+		pr_err("unable to create mpipl kobject\n");
+		return -ENOMEM;
+	}
+
 	/* Export OPAL core sysfs file */
-	rc = sysfs_create_bin_file(opal_kobj, &opal_core_attr);
+	rc = sysfs_create_group(mpipl_kobj, &mpipl_group);
-	if (rc != 0) {
+	if (rc) {
-		pr_err("Failed to export /sys/firmware/opal/core\n");
+		pr_err("mpipl sysfs group creation failed (%d)", rc);
 		opalcore_cleanup();
 		return rc;
 	}
-
+	/* The /sys/firmware/opal/core is moved to /sys/firmware/opal/mpipl/
-	rc = sysfs_create_file(kernel_kobj, &opalcore_rel_attr.attr);
+	 * directory, need to create symlink at old location to maintain
+	 * backward compatibility.
+	 */
+	rc = compat_only_sysfs_link_entry_to_kobj(opal_kobj, mpipl_kobj,
+						  "core", NULL);
 	if (rc) {
-		pr_warn("unable to create sysfs file fadump_release_opalcore (%d)\n",
+		pr_err("unable to create core symlink (%d)\n", rc);
-			rc);
+		return rc;
 	}
 
 	return 0;