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

[Michael Walle]

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