From: frowand.list@gmail.com
To: "Rob Herring" <robh+dt@kernel.org>,
"Clément Léger" <clement.leger@bootlin.com>
Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
Lizhi Hou <lizhi.hou@xilinx.com>,
Allan Nielsen <allan.nielsen@microchip.com>,
Horatiu Vultur <horatiu.vultur@microchip.com>,
Steen Hegelund <steen.hegelund@microchip.com>,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: [PATCH 1/2] of: create of_root if no dtb provided
Date: Thu, 23 Jun 2022 22:43:26 -0500 [thread overview]
Message-ID: <20220624034327.2542112-2-frowand.list@gmail.com> (raw)
In-Reply-To: <20220624034327.2542112-1-frowand.list@gmail.com>
From: Frank Rowand <frank.rowand@sony.com>
When enabling CONFIG_OF on a platform where of_root is not populated by
firmware, we end up without a root node. In order to apply overlays and
create subnodes of the root node, we need one. Create this root node
by unflattening an empty builtin dtb.
If firmware provides a flattened device tree (FDT) then the FDT is
unflattened via setup_arch(). setup_of() is called immediately
after setup_arch(), and will create the default root node if it
does not exist.
Signed-off-by: Frank Rowand <frank.rowand@sony.com>
---
This patch modifies init/main.c. It was not clear to me whether
to add Linus to the distribution, or if the change should flow
through Rob. (I did not add Linus.)
drivers/of/Makefile | 2 +-
drivers/of/fdt.c | 19 ++++++++++++++++++-
include/linux/of_fdt.h | 2 ++
init/main.c | 2 ++
4 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index e0360a44306e..cbae92c5ed02 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -2,7 +2,7 @@
obj-y = base.o device.o platform.o property.o
obj-$(CONFIG_OF_KOBJ) += kobj.o
obj-$(CONFIG_OF_DYNAMIC) += dynamic.o
-obj-$(CONFIG_OF_FLATTREE) += fdt.o
+obj-$(CONFIG_OF_FLATTREE) += fdt.o empty_root.dtb.o
obj-$(CONFIG_OF_EARLY_FLATTREE) += fdt_address.o
obj-$(CONFIG_OF_PROMTREE) += pdt.o
obj-$(CONFIG_OF_ADDRESS) += address.o
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index a8f5b6532165..d439ded3b6c6 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -33,6 +33,12 @@
#include "of_private.h"
+/*
+ * __dtb_empty_root_begin[] magically created by cmd_dt_S_dtb in
+ * scripts/Makefile.lib
+ */
+extern void *__dtb_empty_root_begin;
+
/*
* of_fdt_limit_memory - limit the number of regions in the /memory node
* @limit: maximum entries
@@ -1332,8 +1338,13 @@ bool __init early_init_dt_scan(void *params)
*/
void __init unflatten_device_tree(void)
{
- __unflatten_device_tree(initial_boot_params, NULL, &of_root,
+ if (!initial_boot_params) {
+ initial_boot_params = (void *) __dtb_empty_root_begin;
+ unflatten_and_copy_device_tree();
+ } else {
+ __unflatten_device_tree(initial_boot_params, NULL, &of_root,
early_init_dt_alloc_memory_arch, false);
+ }
/* Get pointer to "/chosen" and "/aliases" nodes for use everywhere */
of_alias_scan(early_init_dt_alloc_memory_arch);
@@ -1373,6 +1384,12 @@ void __init unflatten_and_copy_device_tree(void)
unflatten_device_tree();
}
+void __init setup_of(void)
+{
+ if (!of_root)
+ unflatten_device_tree();
+}
+
#ifdef CONFIG_SYSFS
static ssize_t of_fdt_raw_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr,
diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index d69ad5bb1eb1..4566876db351 100644
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -81,6 +81,7 @@ extern const void *of_flat_dt_match_machine(const void *default_match,
/* Other Prototypes */
extern void unflatten_device_tree(void);
extern void unflatten_and_copy_device_tree(void);
+extern void setup_of(void);
extern void early_init_devtree(void *);
extern void early_get_first_memblock_info(void *, phys_addr_t *);
#else /* CONFIG_OF_EARLY_FLATTREE */
@@ -91,6 +92,7 @@ static inline void early_init_fdt_reserve_self(void) {}
static inline const char *of_flat_dt_get_machine_name(void) { return NULL; }
static inline void unflatten_device_tree(void) {}
static inline void unflatten_and_copy_device_tree(void) {}
+static inline void of_setup(void) {}
#endif /* CONFIG_OF_EARLY_FLATTREE */
#endif /* __ASSEMBLY__ */
diff --git a/init/main.c b/init/main.c
index 0ee39cdcfcac..8b3a60d14bea 100644
--- a/init/main.c
+++ b/init/main.c
@@ -99,6 +99,7 @@
#include <linux/kcsan.h>
#include <linux/init_syscalls.h>
#include <linux/stackdepot.h>
+#include <linux/of_fdt.h>
#include <net/net_namespace.h>
#include <asm/io.h>
@@ -949,6 +950,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
pr_notice("%s", linux_banner);
early_security_init();
setup_arch(&command_line);
+ setup_of();
setup_boot_config();
setup_command_line(command_line);
setup_nr_cpu_ids();
--
Frank Rowand <frank.rowand@sony.com>
next prev parent reply other threads:[~2022-06-24 3:44 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-24 3:43 [PATCH 0/2] of: populate of_root_node if not set (alternate) frowand.list
2022-06-24 3:43 ` frowand.list [this message]
2022-06-24 12:13 ` [PATCH 1/2] of: create of_root if no dtb provided Clément Léger
2022-06-24 16:44 ` Frank Rowand
2022-06-27 9:11 ` Clément Léger
2022-06-27 17:59 ` Rob Herring
2022-10-11 7:26 ` Clément Léger
2023-01-09 8:40 ` Clément Léger
2023-01-10 6:27 ` Frank Rowand
2023-01-10 8:12 ` Clément Léger
2023-01-24 14:34 ` Frank Rowand
2023-02-20 11:15 ` Clément Léger
2023-02-20 18:51 ` Frank Rowand
2022-06-24 3:43 ` [PATCH 2/2] of: unittest: treat missing of_root as error instead of fixing up frowand.list
2022-06-28 14:36 ` Rob Herring
2022-06-28 19:34 ` Frank Rowand
2023-02-22 3:54 [PATCH 0/2] of: populate of_root_node if not set (alternate) Frank Rowand
2023-02-22 3:54 ` [PATCH 1/2] of: create of_root if no dtb provided Frank Rowand
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