[RFC RFT PATCH v3 0/2] Add nvmem support for dynamic partitions

[RFC RFT PATCH v3 0/2] Add nvmem support for dynamic partitions

[Ansuel Smith]

This very small series comes to fix the very annyoing problem of
partitions declared by parser at runtime NOT supporting nvmem cells
definition.

The current implementation is very generic. The idea is to provide an of
node if defined for everyone and not strictly limit this to nvmem stuff.
But still the actual change is done only for nvmem-cells mtd. (just to
make sure) This can totally change by removing the compatible check.

The idea here is that a user can still use these dynamic parsers
instead of declaring a fixed-partition and also declare how nvmem-cells
are defined for the partition.
This live with the assumption that dynamic partition have always the
same name and they are known. (this is the case for smem-part partition
that would require a bootloader reflash to change and for parsers like
cmdlinepart where the name is always the same.)
With this assumption, it's easy to fix this problem. Just introduce a
new partition node that will declare just these special partition.
Mtdcore then will check if these special declaration are present and
connect the dynamic partition with the OF node present in the dts. Nvmem
will automagically fin the OF node and cells will be works based on the
data provided by the parser.

The initial idea was to create a special nvmem driver with a special
compatible where a user would declare the mtd partition name and this
driver would search it and register the nvmem cells but that became
difficult really fast, mtd notifier system is problematic for this kind
of stuff. So here is the better implementation. A variant of this is
already tested on openwrt where we have devices that use cmdlinepart.
(that current variant have defined in the dts the exact copy of
cmdlinepart in the fixed-partition scheme and we patched the cmdlinepart
parser to scan this fixed-partition node (that is ignored as cmdlinepart
have priority) and connect the dynamic partition with the dts node)

I provided an example of this in the documentation commit.
In short it's needed to add to the partitions where the compatible parser
is declared, a partition with just the label declared (instead of the reg).
Then declare some nvmem-cells and it will all work at runtime.
Mtdcore will check if a node with the same label is present and assign an
OF node to the MTD.

I currently tested this on my device that have smem-part and the
gmac driver use nvmem to get the mac-address. This works correctly and
the same address is provided.

v3:
- Fix warning from bot (function not declared as static)
- Updated code to support also node name
- Made partition label optional
v2:
- Simplify this. Drop dynamic-partition
- Fix problem with parser with ko
- Do not pollude mtd_get_of_node
- Fix problem with Documentation

Ansuel Smith (2):
  dt-bindings: mtd: partitions: Document new partition-dynamic nodes
  mtd: core: introduce of support for dynamic partitions

 .../mtd/partitions/partition-dynamic.yaml     | 56 +++++++++++++++++++
 .../mtd/partitions/qcom,smem-part.yaml        |  4 ++
 drivers/mtd/mtdcore.c                         | 56 +++++++++++++++++++
 3 files changed, 116 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mtd/partitions/partition-dynamic.yaml

-- 
2.34.1

[RFC RFT PATCH v3 1/2] dt-bindings: mtd: partitions: Document new partition-dynamic nodes

[Ansuel Smith]

Document new partition-dynamic nodes used to provide an OF node for
partition registred at runtime by parsers. This is required for nvmem
system to declare and detect nvmem-cells.

With these special partitions, the reg / offset is not required.
The node name must be in the form of "partition name"-dynamic.
If the partition can't be displayed using the node name, it's possible
to use the label binding that will be used instead of the node name.
The node name or the label binding is used to match the partition
allocated by the parser at runtime and the parser will provide reg
and offset of the mtd.

NVMEM will use the data from the parser and provide the NVMEM cells
declared in the DTS, "connecting" the dynamic partition with a
static declaration of cells in them.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 .../mtd/partitions/partition-dynamic.yaml     | 56 +++++++++++++++++++
 .../mtd/partitions/qcom,smem-part.yaml        |  4 ++
 2 files changed, 60 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mtd/partitions/partition-dynamic.yaml

diff --git a/Documentation/devicetree/bindings/mtd/partitions/partition-dynamic.yaml b/Documentation/devicetree/bindings/mtd/partitions/partition-dynamic.yaml
new file mode 100644
index 000000000000..e0efa58e4fac
--- /dev/null
+++ b/Documentation/devicetree/bindings/mtd/partitions/partition-dynamic.yaml
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mtd/partitions/partition-dynamic.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Dynamic Partition
+
+description: |
+  This binding describes a single flash partition that is dynamically allocated
+  by a dedicated parser that is not a fixed-partition parser.
+
+  A dynamic partition require the node ending with the "-dynamic" tag and if the
+  dynamic partition name can't be displayed using the node name, the label
+  properties can be used. The node name or the label have to match the dynamic
+  partition allocated by the parser.
+
+  These special partition definition can be used to give a dynamic partition
+  an OF node to declare NVMEM cells. An example is declaring the partition
+  label and all the NVMEM cells in it. The parser will detect the correct reg
+  and offset and the NVMEM will register the cells in it based on the data
+  extracted by the parser.
+
+maintainers:
+  - Ansuel Smith <ansuelsmth@gmail.com>
+
+properties:
+  label:
+    description: The label / name for the partition assigned by the parser at
+      runtime. This is needed for sybsystem like NVMEM to define cells and
+      register with this OF node.
+
+additionalProperties: true
+
+examples:
+  - |
+    flash {
+      partitions {
+        compatible = "qcom,smem-part";
+
+        art-dynamic {
+          compatible = "nvmem-cells";
+          #address-cells = <1>;
+          #size-cells = <1>;
+          label = "0:art";
+
+          macaddr_art_0: macaddr@0 {
+            reg = <0x0 0x6>;
+          };
+
+          macaddr_art_6: macaddr@6 {
+            reg = <0x6 0x6>;
+          };
+        };
+      };
+    };
diff --git a/Documentation/devicetree/bindings/mtd/partitions/qcom,smem-part.yaml b/Documentation/devicetree/bindings/mtd/partitions/qcom,smem-part.yaml
index cf3f8c1e035d..1d7d9b3378c3 100644
--- a/Documentation/devicetree/bindings/mtd/partitions/qcom,smem-part.yaml
+++ b/Documentation/devicetree/bindings/mtd/partitions/qcom,smem-part.yaml
@@ -19,6 +19,10 @@ properties:
   compatible:
     const: qcom,smem-part
 
+patternProperties:
+  "-dynamic$":
+    $ref: "partition-dynamic.yaml#"
+
 required:
   - compatible
 
-- 
2.34.1

[RFC RFT PATCH v3 2/2] mtd: core: introduce of support for dynamic partitions

[Ansuel Smith]

We have many parser that register mtd partitions at runtime. One example
is the cmdlinepart or the smem-part parser where the compatible is defined
in the dts and the partitions gets detected and registered by the
parser. This is problematic for the NVMEM subsystem that requires an OF node
to detect NVMEM cells.

To fix this problem, introduce an additional logic that will try to
assign an OF node to the MTD if declared.

On MTD addition, it will be checked if the MTD has an OF node and if
not declared will check if a partition with the same name / label is
declared in DTS. If an exact match is found, the partition dynamically
allocated by the parser will have a connected OF node.

The NVMEM subsystem will detect the OF node and register any NVMEM cells
declared statically in the DTS.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 drivers/mtd/mtdcore.c | 56 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 9186268d361b..80e28a288f65 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -563,6 +563,61 @@ static int mtd_nvmem_add(struct mtd_info *mtd)
 	return 0;
 }
 
+static void mtd_check_of_node(struct mtd_info *mtd)
+{
+	struct device_node *partitions, *parent_dn, *mtd_dn = NULL;
+	const char *mtd_name, *suffix = "-dynamic";
+	int plen, suffix_len = 8;
+	struct mtd_info *parent;
+	bool found = false;
+
+	/* Check if MTD already has a device node */
+	if (dev_of_node(&mtd->dev))
+		return;
+
+	/* Check if a partitions node exist */
+	parent = mtd->parent;
+	parent_dn = dev_of_node(&parent->dev);
+	if (!parent_dn)
+		return;
+
+	partitions = of_get_child_by_name(parent_dn, "partitions");
+	if (!partitions)
+		goto exit_parent;
+
+	/* Search if a partition is defined with the same name */
+	for_each_child_of_node(partitions, mtd_dn) {
+		mtd_name = of_get_property(mtd_dn, "label", &plen);
+		if (!mtd_name) {
+			mtd_name = of_get_property(mtd_dn, "name", &plen);
+
+			/* Check correct suffix */
+			if (plen <= suffix_len ||
+			    strncmp(mtd_name + plen - suffix_len, suffix, suffix_len))
+				continue;
+
+			plen = plen - suffix_len;
+		}
+
+		if (!strncmp(mtd->name, mtd_name, plen)) {
+			found = true;
+			break;
+		}
+	}
+
+	if (!found)
+		goto exit_partitions;
+
+	/* Set of_node only for nvmem */
+	if (of_device_is_compatible(mtd_dn, "nvmem-cells"))
+		mtd_set_of_node(mtd, mtd_dn);
+
+exit_partitions:
+	of_node_put(partitions);
+exit_parent:
+	of_node_put(parent_dn);
+}
+
 /**
  *	add_mtd_device - register an MTD device
  *	@mtd: pointer to new MTD device info structure
@@ -668,6 +723,7 @@ int add_mtd_device(struct mtd_info *mtd)
 	mtd->dev.devt = MTD_DEVT(i);
 	dev_set_name(&mtd->dev, "mtd%d", i);
 	dev_set_drvdata(&mtd->dev, mtd);
+	mtd_check_of_node(mtd);
 	of_node_get(mtd_get_of_node(mtd));
 	error = device_register(&mtd->dev);
 	if (error)
-- 
2.34.1