dt-bindings: nvmem: u-boot,env: Add support for u-boot,env-size

Add support for u-boot,env-size new property.

Permit to declare a custom size of the U-Boot env that differs than the partition size where the U-Boot env is located.

U-Boot env is validated by calculating the CRC32 on the entire env and in some specific case, the env size might differ from the partition size resulting in wrong CRC32 calculation than the expected one saved at the start of the partition.

This happens when U-Boot is compiled by hardcoding a specific env size but the env is actually placed in a bigger partition, resulting in needing to provide a custom value.

Declaring this property, this value will be used for NVMEM size instead of the mtd partition.

Add also an example to make it clear the scenario of mismatched partition size and actual U-Boot env.

Signed-off-by Christian Marangi <[email protected]>

---
 .../devicetree/bindings/nvmem/u-boot,env.yaml | 47 +++++++++++++++++++
 1 file changed, 47 insertions(+)

Documentation/devicetree/bindings/nvmem/u-boot,env.yaml +47 -0

index 36d97fb87865..3970725a2c57 100644
@@ -44,6 +44,24 @@ properties:
   reg:
     maxItems: 1
 
+  u-boot,env-size:
+    description: |
+      Permit to declare a custom size of the U-Boot env that differs than the
+      partition size where the U-Boot env is located.
+
+      U-Boot env is validated by calculating the CRC32 on the entire env
+      and in some specific case, the env size might differ from the partition
+      size resulting in wrong CRC32 calculation than the expected one saved at
+      the start of the partition.
+
+      This happens when U-Boot is compiled by hardcoding a specific env size
+      but the env is actually placed in a bigger partition, resulting in needing
+      to provide a custom value.
+
+      Declaring this property, this value will be used for NVMEM size instead of
+      the mtd partition.
+    $ref: /schemas/types.yaml#/definitions/uint32
+
   bootcmd:
     type: object
     description: Command to use for automatic booting

@@ -99,3 +117,32 @@ examples:
             };
         };
     };
+  - |
+    partitions {
+        compatible = "fixed-partitions";
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        partition@0 {
+            reg = <0x0 0xc80000>;
+            label = "qcadata";
+            read-only;
+        };
+
+        partition@c80000 {
+            label = "APPSBL";
+            reg = <0xc80000 0x500000>;
+            read-only;
+        };
+
+        partition@1180000 {
+            compatible = "u-boot,env";
+            reg = <0x1180000 0x80000>;
+
+            u-boot,env-size = <0x40000>;
+
+            mac1: ethaddr {
+                #nvmem-cell-cells = <1>;
+            };
+        };
+    };

Signature · 1 line

2.40.1

Quoted 5 lines · Christian Marangi

Add support for u-boot,env-size new property.

Permit to declare a custom size of the U-Boot env that differs than the partition size where the U-Boot env is located.

Quoted 4 lines

U-Boot env is validated by calculating the CRC32 on the entire env and in some specific case, the env size might differ from the partition size resulting in wrong CRC32 calculation than the expected one saved at the start of the partition.

Why can't you just change the partition size? There is no size really because it is just defined in DT.

Quoted 4 lines

This happens when U-Boot is compiled by hardcoding a specific env size but the env is actually placed in a bigger partition, resulting in needing to provide a custom value.

If u-boot is compiled that way, then shouldn't it have that size contained within it? What happens when the DT doesn't match?

Quoted 6 lines

Declaring this property, this value will be used for NVMEM size instead of the mtd partition.

Add also an example to make it clear the scenario of mismatched partition size and actual U-Boot env.

If we do have this, then perhaps there is a generic need for a data size property.

Quoted 71 lines

Signed-off-by Christian Marangi <[email protected]>

---
 .../devicetree/bindings/nvmem/u-boot,env.yaml | 47 +++++++++++++++++++
 1 file changed, 47 insertions(+)

Documentation/devicetree/bindings/nvmem/u-boot,env.yaml +47 -0

index 36d97fb87865..3970725a2c57 100644
@@ -44,6 +44,24 @@ properties:
   reg:
     maxItems: 1
 
+  u-boot,env-size:
+    description: |
+      Permit to declare a custom size of the U-Boot env that differs than the
+      partition size where the U-Boot env is located.
+
+      U-Boot env is validated by calculating the CRC32 on the entire env
+      and in some specific case, the env size might differ from the partition
+      size resulting in wrong CRC32 calculation than the expected one saved at
+      the start of the partition.
+
+      This happens when U-Boot is compiled by hardcoding a specific env size
+      but the env is actually placed in a bigger partition, resulting in needing
+      to provide a custom value.
+
+      Declaring this property, this value will be used for NVMEM size instead of
+      the mtd partition.
+    $ref: /schemas/types.yaml#/definitions/uint32
+
   bootcmd:
     type: object
     description: Command to use for automatic booting

@@ -99,3 +117,32 @@ examples:
             };
         };
     };
+  - |
+    partitions {
+        compatible = "fixed-partitions";
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        partition@0 {
+            reg = <0x0 0xc80000>;
+            label = "qcadata";
+            read-only;
+        };
+
+        partition@c80000 {
+            label = "APPSBL";
+            reg = <0xc80000 0x500000>;
+            read-only;
+        };
+
+        partition@1180000 {
+            compatible = "u-boot,env";
+            reg = <0x1180000 0x80000>;
+
+            u-boot,env-size = <0x40000>;
+
+            mac1: ethaddr {
+                #nvmem-cell-cells = <1>;
+            };
+        };
+    };

Signature · 1 line

2.40.1