powerpc: Add SCOM infrastructure

SCOM is a side-band configuration bus implemented on some processors.
This code provides a way for code to map and operate on devices via
SCOM, while the details of how that is implemented is left up to a
SCOM "controller" in the platform code.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

3 files changed, 201 insertions, 0 deletions

diff --git a/arch/powerpc/sysdev/Kconfig b/arch/powerpc/sysdev/Kconfig
index cfc18770af79..d775fd148d13 100644
--- a/arch/powerpc/sysdev/Kconfig
+++ b/arch/powerpc/sysdev/Kconfig
@@ -15,3 +15,10 @@ config PPC_MSI_BITMAP
 
 source "arch/powerpc/sysdev/xics/Kconfig"
 
+config PPC_SCOM
+	bool
+
+config SCOM_DEBUGFS
+	bool "Expose SCOM controllers via debugfs"
+	depends on PPC_SCOM
+	default n
diff --git a/arch/powerpc/sysdev/Makefile b/arch/powerpc/sysdev/Makefile
index 9516e7598573..6076e0074a87 100644
--- a/arch/powerpc/sysdev/Makefile
+++ b/arch/powerpc/sysdev/Makefile
@@ -58,6 +58,8 @@ ifeq ($(CONFIG_SUSPEND),y)
 obj-$(CONFIG_6xx)		+= 6xx-suspend.o
 endif
 
+obj-$(CONFIG_PPC_SCOM)		+= scom.o
+
 subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
 
 obj-$(CONFIG_PPC_XICS)		+= xics/
diff --git a/arch/powerpc/sysdev/scom.c b/arch/powerpc/sysdev/scom.c
new file mode 100644
index 000000000000..b2593ce30c9b
--- /dev/null
+++ b/arch/powerpc/sysdev/scom.c
@@ -0,0 +1,192 @@
+/*
+ * Copyright 2010 Benjamin Herrenschmidt, IBM Corp
+ *                <benh@kernel.crashing.org>
+ *     and        David Gibson, IBM Corporation.
+ *
+ *   This program is free software;  you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program;  if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/debugfs.h>
+#include <linux/slab.h>
+#include <asm/prom.h>
+#include <asm/scom.h>
+
+const struct scom_controller *scom_controller;
+EXPORT_SYMBOL_GPL(scom_controller);
+
+struct device_node *scom_find_parent(struct device_node *node)
+{
+	struct device_node *par, *tmp;
+	const u32 *p;
+
+	for (par = of_node_get(node); par;) {
+		if (of_get_property(par, "scom-controller", NULL))
+			break;
+		p = of_get_property(par, "scom-parent", NULL);
+		tmp = par;
+		if (p == NULL)
+			par = of_get_parent(par);
+		else
+			par = of_find_node_by_phandle(*p);
+		of_node_put(tmp);
+	}
+	return par;
+}
+EXPORT_SYMBOL_GPL(scom_find_parent);
+
+scom_map_t scom_map_device(struct device_node *dev, int index)
+{
+	struct device_node *parent;
+	unsigned int cells, size;
+	const u32 *prop;
+	u64 reg, cnt;
+	scom_map_t ret;
+
+	parent = scom_find_parent(dev);
+
+	if (parent == NULL)
+		return 0;
+
+	prop = of_get_property(parent, "#scom-cells", NULL);
+	cells = prop ? *prop : 1;
+
+	prop = of_get_property(dev, "scom-reg", &size);
+	if (!prop)
+		return 0;
+	size >>= 2;
+
+	if (index >= (size / (2*cells)))
+		return 0;
+
+	reg = of_read_number(&prop[index * cells * 2], cells);
+	cnt = of_read_number(&prop[index * cells * 2 + cells], cells);
+
+	ret = scom_map(parent, reg, cnt);
+	of_node_put(parent);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(scom_map_device);
+
+#ifdef CONFIG_SCOM_DEBUGFS
+struct scom_debug_entry {
+	struct device_node *dn;
+	unsigned long addr;
+	scom_map_t map;
+	spinlock_t lock;
+	char name[8];
+	struct debugfs_blob_wrapper blob;
+};
+
+static int scom_addr_set(void *data, u64 val)
+{
+	struct scom_debug_entry *ent = data;
+
+	ent->addr = 0;
+	scom_unmap(ent->map);
+
+	ent->map = scom_map(ent->dn, val, 1);
+	if (scom_map_ok(ent->map))
+		ent->addr = val;
+	else
+		return -EFAULT;
+
+	return 0;
+}
+
+static int scom_addr_get(void *data, u64 *val)
+{
+	struct scom_debug_entry *ent = data;
+	*val = ent->addr;
+	return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(scom_addr_fops, scom_addr_get, scom_addr_set,
+			"0x%llx\n");
+
+static int scom_val_set(void *data, u64 val)
+{
+	struct scom_debug_entry *ent = data;
+
+	if (!scom_map_ok(ent->map))
+		return -EFAULT;
+
+	scom_write(ent->map, 0, val);
+
+	return 0;
+}
+
+static int scom_val_get(void *data, u64 *val)
+{
+	struct scom_debug_entry *ent = data;
+
+	if (!scom_map_ok(ent->map))
+		return -EFAULT;
+
+	*val = scom_read(ent->map, 0);
+	return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(scom_val_fops, scom_val_get, scom_val_set,
+			"0x%llx\n");
+
+static int scom_debug_init_one(struct dentry *root, struct device_node *dn,
+			       int i)
+{
+	struct scom_debug_entry *ent;
+	struct dentry *dir;
+
+	ent = kzalloc(sizeof(*ent), GFP_KERNEL);
+	if (!ent)
+		return -ENOMEM;
+
+	ent->dn = of_node_get(dn);
+	ent->map = SCOM_MAP_INVALID;
+	spin_lock_init(&ent->lock);
+	snprintf(ent->name, 8, "scom%d", i);
+	ent->blob.data = dn->full_name;
+	ent->blob.size = strlen(dn->full_name);
+
+	dir = debugfs_create_dir(ent->name, root);
+	if (!dir) {
+		of_node_put(dn);
+		kfree(ent);
+		return -1;
+	}
+
+	debugfs_create_file("addr", 0600, dir, ent, &scom_addr_fops);
+	debugfs_create_file("value", 0600, dir, ent, &scom_val_fops);
+	debugfs_create_blob("path", 0400, dir, &ent->blob);
+
+	return 0;
+}
+
+static int scom_debug_init(void)
+{
+	struct device_node *dn;
+	struct dentry *root;
+	int i, rc;
+
+	root = debugfs_create_dir("scom", powerpc_debugfs_root);
+	if (!root)
+		return -1;
+
+	i = rc = 0;
+	for_each_node_with_property(dn, "scom-controller")
+		rc |= scom_debug_init_one(root, dn, i++);
+
+	return rc;
+}
+device_initcall(scom_debug_init);
+#endif /* CONFIG_SCOM_DEBUGFS */