| Message ID | 20221018154202.4634-2-zajec5@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [V3,1/2] dt-bindings: mtd: partitions: u-boot: allow dynamic subpartitions | expand |
On Tue, 18 Oct 2022 17:42:02 +0200, Rafał Miłecki wrote: > From: Rafał Miłecki <rafal@milecki.pl> > > Broadcom uses U-Boot for a lot of their bcmbca familiy chipsets. U-Boot > stores its configuration in an environment data block. > > Such blocks are usually stored on flash as a separated partition at > hardcoded address. Broadcom however decided to: > 1. Store env data block inside U-Boot partition > 2. Avoid sticking to hardcoded offsets > 3. Use custom header with "uEnv" magic and env data length > > Example (length 0x4000): > $ hexdump -n 32 -C -s 0x40000 /dev/mtdblock0 > 00040000 76 6e 45 75 00 40 00 00 34 89 7a 82 49 4d 41 47 |vnEu.@..4.z.IMAG| > 00040010 45 3d 4e 41 4e 44 3a 31 4d 2c 31 30 32 34 4d 00 |E=NAND:1M,1024M.| > (0x40000 offset is unit specific and can change) > > Starting with the commit 118f3fbe517f4 ("dt-bindings: mtd: partitions: > support label/name only partition") DT can describe partitions matching > them by a name (without specifying actual address). With that feature > and this binding change it's possible to: > 1. Specify DT node for Broadcom's U-Boot env data subpartition > 2. Add nodes for specific environment data variables > 3. Reference them as NVMEM cells > > This binding is unlikely to help Broadcom's U-Boot. U-Boot SPL needs to > find environment data early (before it accesses DTB) and it does that by > looking for an "uEnv" magic. Dirty way. > > This binding can however be used by operating systems. It allows > describing cleanly U-Boot, its env data and variables. It tells > operating system about Broadcom-specific env data so it can parse it. > > Signed-off-by: Rafał Miłecki <rafal@milecki.pl> > --- > V2: Work on better commit body & add example > V3: Avoid duplicated "mac" label > --- > .../devicetree/bindings/nvmem/u-boot,env.yaml | 21 +++++++++++++++++++ > 1 file changed, 21 insertions(+) > Applied, thanks!
diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml index e96bca99f2d9..cbc5c69fd405 100644 --- a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml +++ b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml @@ -38,6 +38,8 @@ properties: const: u-boot,env-redundant-bool - description: Two redundant blocks with active having higher counter const: u-boot,env-redundant-count + - description: Broadcom's variant with custom header + const: brcm,env reg: maxItems: 1 @@ -73,3 +75,22 @@ examples: }; }; }; + - | + partitions { + compatible = "fixed-partitions"; + #address-cells = <1>; + #size-cells = <1>; + + partition@0 { + reg = <0x0 0x100000>; + compatible = "brcm,u-boot"; + label = "u-boot"; + + partition-u-boot-env { + compatible = "brcm,env"; + + ethaddr { + }; + }; + }; + };