Re: [RFC PATCH 0/4] mtd: core: OTP nvmem provider support

From: Michael Walle
Date: Tue Mar 30 2021 - 05:50:12 EST


Hi Srinivas,

Am 2021-03-30 11:42, schrieb Srinivas Kandagatla:
On 22/03/2021 18:19, Michael Walle wrote:
The goal is to fetch a (base) MAC address from the OTP region of a SPI NOR
flash.

This is the first part, where I try to add the nvmem provider support to
the MTD core.

I'm not sure about the device tree bindings. Consider the following two
variants:

(1)
flash@0 {
..

otp {
compatible = "mtd-user-otp";
#address-cells = <1>;
#size-cells = <1>;

serial-number@0 {
reg = <0x0 0x8>;
};
};
};

(2)
flash@0 {
..

otp {
compatible = "mtd-user-otp";
#address-cells = <1>;
#size-cells = <1>;

some-useful-name {
compatible = "nvmem-cells";

serial-number@0 {
reg = <0x0 0x8>;
};
};
};
};

Both bindings use a subnode "opt[-N]". We cannot have the nvmem cells as
children to the flash node because of the legacy partition binding.

(1) seems to be the form which is used almost everywhere in the kernel.
That is, the nvmem cells are just children of the parent node.

(2) seem to be more natural, because there might also be other properties
inside the otp subnode and might be more future-proof.

At the moment this patch implements (1).



Have you looked at this series[1], are you both trying to do the same thing?

Yes, I've seen these, but they are for MTD partitions. OTP regions are not
MTD partitions (and cannot be mapped to them).

-michael


[1] https://lore.kernel.org/linux-mtd/20210312062830.20548-2-ansuelsmth@xxxxxxxxx/T/

--srini


Michael Walle (4):
nvmem: core: allow specifying of_node
dt-bindings: mtd: add YAML schema for the generic MTD bindings
dt-bindings: mtd: add OTP bindings
mtd: core: add OTP nvmem provider support

.../devicetree/bindings/mtd/common.txt | 16 +-
.../devicetree/bindings/mtd/mtd.yaml | 110 +++++++++++++
drivers/mtd/mtdcore.c | 149 ++++++++++++++++++
drivers/nvmem/core.c | 4 +-
include/linux/mtd/mtd.h | 2 +
include/linux/nvmem-provider.h | 2 +
6 files changed, 267 insertions(+), 16 deletions(-)
create mode 100644 Documentation/devicetree/bindings/mtd/mtd.yaml