x86, olpc: Add OLPC device-tree support

Make use of PROC_DEVICETREE to export the tree, and sparc's PROMTREE code to
call into OLPC's Open Firmware to build the tree.

v5: fix buglet with root node check (introduced in v4)

v4: address some minor style issues pointed out by Grant, and explicitly cast
    negative phandle checks to s32.

v3: rename olpc_prom to olpc_dt
  - rework Kconfig entries
  - drop devtree build hook from proc, instead adding a call to x86's
    paging_init (similarly to how sparc64 does it)
  - switch allocation from using slab to alloc_bootmem.  this allows
    the DT to be built earlier during boot (during setup_arch); the
    downside is that there are some 1200 bootmem reservations that are
    done during boot.  Not ideal..
  - add a helper olpc_ofw_is_installed function to test for the
    existence and successful detection of OLPC's OFW.

Signed-off-by: Andres Salomon <dilinger@queued.net>
LKML-Reference: <20101116220952.26526a80@queued.net>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

3 files changed, 171 insertions, 0 deletions

diff --git a/arch/x86/platform/olpc/Makefile b/arch/x86/platform/olpc/Makefile
index c31b8fcb5a86..e797428b163b 100644
--- a/arch/x86/platform/olpc/Makefile
+++ b/arch/x86/platform/olpc/Makefile
@@ -1,3 +1,4 @@
 obj-$(CONFIG_OLPC)              += olpc.o
 obj-$(CONFIG_OLPC_XO1)          += olpc-xo1.o
 obj-$(CONFIG_OLPC_OPENFIRMWARE) += olpc_ofw.o
+obj-$(CONFIG_OLPC_OPENFIRMWARE_DT)      += olpc_dt.o
diff --git a/arch/x86/platform/olpc/olpc_dt.c b/arch/x86/platform/olpc/olpc_dt.c
new file mode 100644
index 000000000000..70546975a920
--- /dev/null
+++ b/arch/x86/platform/olpc/olpc_dt.c
@@ -0,0 +1,165 @@
+/*
+ * OLPC-specific OFW device tree support code.
+ *
+ * Paul Mackerras       August 1996.
+ * Copyright (C) 1996-2005 Paul Mackerras.
+ *
+ *  Adapted for 64bit PowerPC by Dave Engebretsen and Peter Bergner.
+ *    {engebret|bergner}@us.ibm.com
+ *
+ *  Adapted for sparc by David S. Miller davem@davemloft.net
+ *  Adapted for x86/OLPC by Andres Salomon <dilinger@queued.net>
+ *
+ *      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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/bootmem.h>
+#include <linux/of.h>
+#include <linux/of_pdt.h>
+#include <asm/olpc_ofw.h>
+
+static phandle __init olpc_dt_getsibling(phandle node)
+{
+        const void *args[] = { (void *)node };
+        void *res[] = { &node };
+
+        if ((s32)node == -1)
+                return 0;
+
+        if (olpc_ofw("peer", args, res) || (s32)node == -1)
+                return 0;
+
+        return node;
+}
+
+static phandle __init olpc_dt_getchild(phandle node)
+{
+        const void *args[] = { (void *)node };
+        void *res[] = { &node };
+
+        if ((s32)node == -1)
+                return 0;
+
+        if (olpc_ofw("child", args, res) || (s32)node == -1) {
+                pr_err("PROM: %s: fetching child failed!\n", __func__);
+                return 0;
+        }
+
+        return node;
+}
+
+static int __init olpc_dt_getproplen(phandle node, const char *prop)
+{
+        const void *args[] = { (void *)node, prop };
+        int len;
+        void *res[] = { &len };
+
+        if ((s32)node == -1)
+                return -1;
+
+        if (olpc_ofw("getproplen", args, res)) {
+                pr_err("PROM: %s: getproplen failed!\n", __func__);
+                return -1;
+        }
+
+        return len;
+}
+
+static int __init olpc_dt_getproperty(phandle node, const char *prop,
+                char *buf, int bufsize)
+{
+        int plen;
+
+        plen = olpc_dt_getproplen(node, prop);
+        if (plen > bufsize || plen < 1) {
+                return -1;
+        } else {
+                const void *args[] = { (void *)node, prop, buf, (void *)plen };
+                void *res[] = { &plen };
+
+                if (olpc_ofw("getprop", args, res)) {
+                        pr_err("PROM: %s: getprop failed!\n", __func__);
+                        return -1;
+                }
+        }
+
+        return plen;
+}
+
+static int __init olpc_dt_nextprop(phandle node, char *prev, char *buf)
+{
+        const void *args[] = { (void *)node, prev, buf };
+        int success;
+        void *res[] = { &success };
+
+        buf[0] = '\0';
+
+        if ((s32)node == -1)
+                return -1;
+
+        if (olpc_ofw("nextprop", args, res) || success != 1)
+                return -1;
+
+        return 0;
+}
+
+static int __init olpc_dt_pkg2path(phandle node, char *buf,
+                const int buflen, int *len)
+{
+        const void *args[] = { (void *)node, buf, (void *)buflen };
+        void *res[] = { len };
+
+        if ((s32)node == -1)
+                return -1;
+
+        if (olpc_ofw("package-to-path", args, res) || *len < 1)
+                return -1;
+
+        return 0;
+}
+
+static unsigned int prom_early_allocated __initdata;
+
+void * __init prom_early_alloc(unsigned long size)
+{
+        void *res;
+
+        res = alloc_bootmem(size);
+        if (res)
+                memset(res, 0, size);
+
+        prom_early_allocated += size;
+
+        return res;
+}
+
+static struct of_pdt_ops prom_olpc_ops __initdata = {
+        .nextprop = olpc_dt_nextprop,
+        .getproplen = olpc_dt_getproplen,
+        .getproperty = olpc_dt_getproperty,
+        .getchild = olpc_dt_getchild,
+        .getsibling = olpc_dt_getsibling,
+        .pkg2path = olpc_dt_pkg2path,
+};
+
+void __init olpc_dt_build_devicetree(void)
+{
+        phandle root;
+
+        if (!olpc_ofw_is_installed())
+                return;
+
+        root = olpc_dt_getsibling(0);
+        if (!root) {
+                pr_err("PROM: unable to get root node from OFW!\n");
+                return;
+        }
+        of_pdt_build_devicetree(root, &prom_olpc_ops);
+
+        pr_info("PROM DT: Built device tree with %u bytes of memory.\n",
+                        prom_early_allocated);
+}
diff --git a/arch/x86/platform/olpc/olpc_ofw.c b/arch/x86/platform/olpc/olpc_ofw.c
index 787320464379..e7604f62870d 100644
--- a/arch/x86/platform/olpc/olpc_ofw.c
+++ b/arch/x86/platform/olpc/olpc_ofw.c
@@ -110,3 +110,8 @@ void __init olpc_ofw_detect(void)
                         (unsigned long)olpc_ofw_cif, (-start) >> 20);
         reserve_top_address(-start);
 }
+
+bool __init olpc_ofw_is_installed(void)
+{
+        return olpc_ofw_cif != NULL;
+}