[PATCH 4/8] nvmem: layouts: u-boot-env: add optional "env-size" property

srini
2025-11-14T11:07:01Z

From: Jascha Sundaresan <flizarthanon@gmail.com>

Some devices reserve a larger NVMEM region for the U-Boot environment
than the actual environment data length used by U-Boot itself. The CRC32
in the U-Boot header is calculated over the smaller data length, causing
CRC validation to fail when Linux reads the full partition.

Allow an optional device tree property "env-size" to specify the
environment data size to use for CRC computation.

v2: add missing $ref line to DT binding

Signed-off-by: Jascha Sundaresan <flizarthanon@gmail.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Srinivas Kandagatla <srini@kernel.org>
---
.../devicetree/bindings/nvmem/layouts/u-boot,env.yaml | 7 +++++++
drivers/nvmem/layouts/u-boot-env.c | 4 +++-
2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env.yaml b/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env.yaml
index 56a8f55d4a09..e9e75c38bd11 100644
--- a/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env.yaml
+++ b/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env.yaml
@@ -46,6 +46,12 @@ properties:
type: object
description: Command to use for automatic booting

+ env-size:
+ description:
+ Size in bytes of the environment data used by U-Boot for CRC
+ calculation. If omitted, the full NVMEM region size is used.
+ $ref: /schemas/types.yaml#/definitions/uint32
+
ethaddr:
type: object
description: Ethernet interfaces base MAC address.
@@ -104,6 +110,7 @@ examples:

partition-u-boot-env {
compatible = "brcm,env";
+ env-size = <0x20000>;

ethaddr {
};
diff --git a/drivers/nvmem/layouts/u-boot-env.c b/drivers/nvmem/layouts/u-boot-env.c
index a27eeb08146f..ab32bf1291af 100644
--- a/drivers/nvmem/layouts/u-boot-env.c
+++ b/drivers/nvmem/layouts/u-boot-env.c
@@ -99,10 +99,12 @@ int u_boot_env_parse(struct device *dev, struct nvmem_device *nvmem,
uint32_t crc32;
uint32_t calc;
uint8_t *buf;
+ u32 env_size;
int bytes;
int err;

- dev_size = nvmem_dev_size(nvmem);
+ dev_size = device_property_read_u32(dev, "env-size", &env_size) ?
+ nvmem_dev_size(nvmem) : (size_t)env_size;

buf = kzalloc(dev_size, GFP_KERNEL);
if (!buf) {
--
2.51.0