nvmem: add support for nvmem-cells binding

Recently, nvmem cell and MTD partition bindings were made to coexist:
Partitions can now be compatible = "nvmem-cells"; which registers a
NVMEM provider and interprets its child nodes as cells. Teach barebox
about this. This allows fetching NVMEM cells from MTD partitions and
hostfiles.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20210619034516.6737-5-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

3 files changed, 48 insertions, 6 deletions

diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 6330f3d6e6..53c02dc785 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -3,7 +3,7 @@
 #
 
 obj-$(CONFIG_NVMEM)		+= nvmem_core.o
-nvmem_core-y			:= core.o regmap.o
+nvmem_core-y			:= core.o regmap.o partition.o
 
 obj-$(CONFIG_NVMEM_RMEM)	+= rmem.o
 
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 3c14e390de..c060e627db 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -205,7 +205,7 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 	nvmem->size = config->size;
 	nvmem->dev.parent = config->dev;
 	nvmem->bus = config->bus;
-	np = config->dev->device_node;
+	np = config->cdev ? config->cdev->device_node : config->dev->device_node;
 	nvmem->dev.device_node = np;
 	nvmem->priv = config->priv;
 
@@ -223,10 +223,12 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 		return ERR_PTR(rval);
 	}
 
-	rval = nvmem_register_cdev(nvmem, config->name);
-	if (rval) {
-		kfree(nvmem);
-		return ERR_PTR(rval);
+	if (!config->cdev) {
+		rval = nvmem_register_cdev(nvmem, config->name);
+		if (rval) {
+			kfree(nvmem);
+			return ERR_PTR(rval);
+		}
 	}
 
 	list_add_tail(&nvmem->node, &nvmem_devs);
diff --git a/drivers/nvmem/partition.c b/drivers/nvmem/partition.c
new file mode 100644
index 0000000000..3f0bdc58de
--- /dev/null
+++ b/drivers/nvmem/partition.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <common.h>
+#include <driver.h>
+#include <malloc.h>
+#include <xfuncs.h>
+#include <errno.h>
+#include <init.h>
+#include <io.h>
+#include <linux/nvmem-provider.h>
+
+static int nvmem_cdev_write(void *ctx, unsigned offset, const void *val, size_t bytes)
+{
+	return cdev_write(ctx, val, bytes, offset, 0);
+}
+
+static int nvmem_cdev_read(void *ctx, unsigned offset, void *buf, size_t bytes)
+{
+	return cdev_read(ctx, buf, bytes, offset, 0);
+}
+
+static struct nvmem_bus nvmem_cdev_bus = {
+	.read = nvmem_cdev_read,
+	.write = nvmem_cdev_write,
+};
+
+struct nvmem_device *nvmem_partition_register(struct cdev *cdev)
+{
+	struct nvmem_config config = {};
+
+	config.name = cdev->name;
+	config.dev = cdev->dev;
+	config.cdev = cdev;
+	config.priv = cdev;
+	config.stride = 1;
+	config.word_size = 1;
+	config.size = cdev->size;
+	config.bus = &nvmem_cdev_bus;
+
+	return nvmem_register(&config);
+}