Flash OTP regions can already be read via user space. Some boards have
their serial number or MAC addresses stored in the OTP regions. Add
support for them being a (read-only) nvmem provider.
The API to read the OTP data is already in place. It distinguishes
between factory and user OTP, thus there are up to two different
providers.
Signed-off-by: Michael Walle <mich...@walle.cc>
---
Changes since RFC:
- none
drivers/mtd/mtdcore.c | 149 ++++++++++++++++++++++++++++++++++++++++
include/linux/mtd/mtd.h | 2 +
2 files changed, 151 insertions(+)
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 0bc6871c3863..92201e3d187a 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -777,6 +777,147 @@ static void mtd_set_dev_defaults(struct mtd_info *mtd)
mutex_init(&mtd->master.chrdev_lock);
}
+static ssize_t mtd_otp_size(struct mtd_info *mtd, bool is_user)
+{
+ struct otp_info *info = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ ssize_t size = 0;
+ unsigned int i;
+ size_t retlen;
+ int ret;
+
+ if (is_user)
+ ret = mtd_get_user_prot_info(mtd, PAGE_SIZE, &retlen, info);
+ else
+ ret = mtd_get_fact_prot_info(mtd, PAGE_SIZE, &retlen, info);
+ if (ret)
+ goto err;
+
+ for (i = 0; i < retlen / sizeof(*info); i++) {
+ size += info->length;
+ info++;
+ }
+
+ kfree(info);
+ return size;
+
+err:
+ kfree(info);
+ return ret;
+}
+
+static struct nvmem_device *mtd_otp_nvmem_register(struct mtd_info *mtd,
+ const char *name, int size,
+ nvmem_reg_read_t reg_read,
+ const char *compatible)
+{
+ struct nvmem_device *nvmem = NULL;
+ struct nvmem_config config = {};
+ struct device_node *np;
+
+ /* DT binding is optional */
+ np = of_get_compatible_child(mtd->dev.of_node, compatible);
+
+ /* OTP nvmem will be registered on the physical device */
+ config.dev = mtd->dev.parent;
+ config.name = name;
+ config.id = NVMEM_DEVID_NONE;
+ config.owner = THIS_MODULE;
+ config.type = NVMEM_TYPE_OTP;
+ config.root_only = true;
+ config.reg_read = reg_read;
+ config.size = size;
+ config.of_node = np;
+ config.priv = mtd;
+
+ nvmem = nvmem_register(&config);
+ /* Just ignore if there is no NVMEM support in the kernel */
+ if (IS_ERR(nvmem) && PTR_ERR(nvmem) == -EOPNOTSUPP)
+ nvmem = NULL;
+
+ of_node_put(np);
+
+ return nvmem;
+}
+
+static int mtd_nvmem_user_otp_reg_read(void *priv, unsigned int offset,
+ void *val, size_t bytes)
+{
+ struct mtd_info *mtd = priv;
+ size_t retlen;
+ int ret;
+
+ ret = mtd_read_user_prot_reg(mtd, offset, bytes, &retlen, val);
+ if (ret)
+ return ret;
+
+ return retlen == bytes ? 0 : -EIO;
+}
+
+static int mtd_nvmem_fact_otp_reg_read(void *priv, unsigned int offset,
+ void *val, size_t bytes)
+{
+ struct mtd_info *mtd = priv;
+ size_t retlen;
+ int ret;
+
+ ret = mtd_read_fact_prot_reg(mtd, offset, bytes, &retlen, val);
+ if (ret)
+ return ret;
+
+ return retlen == bytes ? 0 : -EIO;
+}
+
+static int mtd_otp_nvmem_add(struct mtd_info *mtd)
+{
+ struct nvmem_device *nvmem;
+ ssize_t size;
+ int err;
+
+ if (mtd->_get_user_prot_info && mtd->_read_user_prot_reg) {
+ size = mtd_otp_size(mtd, true);
+ if (size < 0)
+ return size;
+
+ if (size > 0) {
+ nvmem = mtd_otp_nvmem_register(mtd, "user-otp", size,
+
mtd_nvmem_user_otp_reg_read,
+ "mtd-user-otp");
+ if (IS_ERR(nvmem)) {
+ dev_err(&mtd->dev, "Failed to register OTP
NVMEM device\n");
+ return PTR_ERR(nvmem);
+ }
+ mtd->otp_user_nvmem = nvmem;
+ }
+ }
+
+ if (mtd->_get_fact_prot_info && mtd->_read_fact_prot_reg) {
+ size = mtd_otp_size(mtd, false);
+ if (size < 0) {
+ err = size;
+ goto err;
+ }
+
+ if (size > 0) {
+ nvmem = mtd_otp_nvmem_register(mtd, "factory-otp", size,
+
mtd_nvmem_fact_otp_reg_read,
+ "mtd-factory-otp");
+ if (IS_ERR(nvmem)) {
+ dev_err(&mtd->dev, "Failed to register OTP
NVMEM device\n");
+ err = PTR_ERR(nvmem);
+ goto err;
+ }
+ mtd->otp_factory_nvmem = nvmem;
+ }
+ }
+
+ return 0;
+
+err:
+ if (mtd->otp_user_nvmem)
+ nvmem_unregister(mtd->otp_user_nvmem);
+ return err;
+}
+
/**
* mtd_device_parse_register - parse partitions and register an MTD device.
*
@@ -852,6 +993,8 @@ int mtd_device_parse_register(struct mtd_info *mtd, const
char * const *types,
register_reboot_notifier(&mtd->reboot_notifier);
}
+ ret = mtd_otp_nvmem_add(mtd);
+
out:
if (ret && device_is_registered(&mtd->dev))
del_mtd_device(mtd);
@@ -873,6 +1016,12 @@ int mtd_device_unregister(struct mtd_info *master)
if (master->_reboot)
unregister_reboot_notifier(&master->reboot_notifier);
+ if (master->otp_user_nvmem)
+ nvmem_unregister(master->otp_user_nvmem);
+
+ if (master->otp_factory_nvmem)
+ nvmem_unregister(master->otp_factory_nvmem);
+
err = del_mtd_partitions(master);
if (err)
return err;
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 4aac200ca8b5..71e751d18c22 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -379,6 +379,8 @@ struct mtd_info {
int usecount;
struct mtd_debug_info dbg;
struct nvmem_device *nvmem;
+ struct nvmem_device *otp_user_nvmem;
+ struct nvmem_device *otp_factory_nvmem;
/*
* Parent device from the MTD partition point of view.
--
2.20.1
