On 6/23/22 21:01, Frank Rowand wrote:
> On 6/23/22 19:15, Frank Rowand wrote:
>> Hi Clement,
>>
>> I said that I would send a patch to do this, but have failed to follow
>> through. Sorry about that.
>>
>>
>> On 6/23/22 06:50, Clément Léger wrote:
>>> 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 with of_fdt_unflatten().
>>>
>>> Co-developed-by: Rob Herring <robh@xxxxxxxxxx>
>>> Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
>>> Signed-off-by: Clément Léger <clement.leger@xxxxxxxxxxx>
>>> ---
>>> drivers/of/Makefile | 2 +-
>>> drivers/of/base.c | 18 ++++++++++++++++--
>>> drivers/of/empty_root.dts | 6 ++++++
>>> 3 files changed, 23 insertions(+), 3 deletions(-)
>>> create mode 100644 drivers/of/empty_root.dts
>>>
>>> diff --git a/drivers/of/Makefile b/drivers/of/Makefile
>>> index e0360a44306e..ce56c8b95c83 100644
>>> --- a/drivers/of/Makefile
>>> +++ b/drivers/of/Makefile
>>> @@ -1,5 +1,5 @@
>>> # SPDX-License-Identifier: GPL-2.0
>>> -obj-y = base.o device.o platform.o property.o
>>> +obj-y = base.o empty_root.dtb.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
>>> diff --git a/drivers/of/base.c b/drivers/of/base.c
>>> index d4f98c8469ed..43e0f027a49c 100644
>>> --- a/drivers/of/base.c
>>> +++ b/drivers/of/base.c
>>> @@ -22,6 +22,7 @@
>>> #include <linux/module.h>
>>> #include <linux/of.h>
>>> #include <linux/of_device.h>
>>> +#include <linux/of_fdt.h>
>>> #include <linux/of_graph.h>
>>> #include <linux/spinlock.h>
>>> #include <linux/slab.h>
>>> @@ -163,6 +164,8 @@ void __of_phandle_cache_inv_entry(phandle handle)
>>> phandle_cache[handle_hash] = NULL;
>>> }
>>>
>>> +extern const char __dtb_empty_root_begin[];
>>> +
>>> void __init of_core_init(void)
>>> {
>>> struct device_node *np;
>>> @@ -176,6 +179,18 @@ void __init of_core_init(void)
>>> pr_err("failed to register existing nodes\n");
>>> return;
>>> }
>>> +
>>> + if (!of_root) {
>>> + void *dt;
>>> + const unsigned long *fdt = (const unsigned long *)
>>> + __dtb_empty_root_begin;
>>> + dt = of_fdt_unflatten_tree(fdt, NULL, &of_root);
>>> + if (!dt) {
>>> + pr_err("Failed to setup empty root dt\n");
>>> + return;
>>> + }
>>> + }
>>> +
>>> for_each_of_allnodes(np) {
>>> __of_attach_node_sysfs(np);
>>> if (np->phandle && !phandle_cache[of_phandle_cache_hash(np->phandle)])
>>> @@ -184,8 +199,7 @@ void __init of_core_init(void)
>>> mutex_unlock(&of_mutex);
>>>
>>> /* Symlink in /proc as required by userspace ABI */
>>> - if (of_root)
>>> - proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
>>> + proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
>>> }
>>
>> This approach is adding an additional method of unflattening the tree.
>> I would prefer to consolidate in a single location.
>>
>> I have leveraged this patch series into a different patch series to
>> accomplish that. I have boot tested with one configuration, but want
>> to test two more configurations before sending the new series. It
>> should only take "a few minutes".
>
> "a few minutes" is taking longer than expected. One of the devicetree
> interrupt unittests is not giving the expected result for one of the
> configurations I am checking.
The test is ok. The problem was unrelated asynchronous output to the
console intermingled with test output.
My suggested alternative patch series is at:
https://lore.kernel.org/r/20220624034327.2542112-1-frowand.list@xxxxxxxxx
-Frank
>
> -Frank
>
>>
>> -Frank
>>
>>>
>>> static struct property *__of_find_property(const struct device_node *np,
>>> diff --git a/drivers/of/empty_root.dts b/drivers/of/empty_root.dts
>>> new file mode 100644
>>> index 000000000000..cf9e97a60f48
>>> --- /dev/null
>>> +++ b/drivers/of/empty_root.dts
>>> @@ -0,0 +1,6 @@
>>> +// SPDX-License-Identifier: GPL-2.0-only
>>> +/dts-v1/;
>>> +
>>> +/ {
>>> +
>>> +};
>>
>
