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of: Create of_root if no dtb provided by firmware

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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(). Otherwise, the call to
unflatten(_and_copy)?_device_tree() will create an empty root node.

We make of_have_populated_dt() return true only if the DTB was loaded by
firmware so that existing callers don't change behavior after this
patch. The call in the of platform code is removed because it prevents
overlays from creating platform devices when the empty root node is
used.

[sboyd@kernel.org: Update of_have_populated_dt() to treat this empty dtb
as not populated. Drop setup_of() initcall]

Signed-off-by: Frank Rowand <frowand.list@gmail.com>
Link: https://lore.kernel.org/r/20230317053415.2254616-2-frowand.list@gmail.com
Cc: Rob Herring <robh+dt@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20240217010557.2381548-3-sboyd@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
This commit is contained in:
Frank Rowand
2024-02-16 17:05:51 -08:00
committed by Rob Herring
parent dc1460fe1b
commit 7b937cc243
6 changed files with 55 additions and 18 deletions
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3
drivers/of/platform.c
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@@ -512,9 +512,6 @@ static int __init of_platform_default_populate_init(void)
device_links_supplier_sync_state_pause();
if (!of_have_populated_dt())
return -ENODEV;
if (IS_ENABLED(CONFIG_PPC)) {
struct device_node *boot_display = NULL;
struct platform_device *dev;