bootsource: allow DT aliases and bootrom numbering to differ

So far, we had no explicit mapping table between bootsource_instance
and device id numbering in barebox and mostly depended on DT aliases
reflecting the numbering of the bootrom. Add a new bootsource_set()
that optionally consults a mapping table in the DT to arrive at the
correct numbers.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20220720055042.3510276-3-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 36 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/barebox/aliases.rst b/Documentation/devicetree/bindings/barebox/aliases.rst
new file mode 100644
index 0000000000..527cc85ef6
--- /dev/null
+++ b/Documentation/devicetree/bindings/barebox/aliases.rst
@@ -0,0 +1,36 @@
+barebox DT aliases
+==================
+
+barebox can use the properties in the ``/aliases`` node to arrive
+at deterministic names for devices, e.g.::
+
+.. code-block:: none
+   / {
+   	aliases {
+   		mmc0 = &sdhci;
+   		wdog0 = &iwdg;
+   	};
+   };
+
+will assign the MMC device created from probing the node at ``&sdhci``
+the name ``/dev/mmc0``. Similarly, the watchdog device created from
+probing the node at ``&iwdg`` will be named ``wdog0``.
+
+By default, barebox will assume the aliases in the DT to align with
+the bootsource communicated by the firmware. If this is not the case,
+a device tree override is possible via an
+``/aliases/barebox,bootsource-${bootsource}${bootsource_instance}``
+property:
+
+.. code-block:: none
+
+  &{/aliases} {
+	mmc0 = &sdmmc0;
+	mmc1 = &sdhci;
+	barebox,bootsource-mmc0 = &sdhci;
+	barebox,bootsource-mmc1 = &sdmmc0;
+  };
+
+This will ensure that when booting from MMC, ``/dev/mmc${bootsource_instance}``
+will point at the correct boot device, despite bootrom and board DT alias
+order being different.