Re: [RFC PATCH v6 1/2] hw/misc/sifive_u_otp: Add write function and write-once protection

[Bin Meng]

Hi Green,

On Mon, Sep 28, 2020 at 6:12 PM Green Wan <green.wan@sifive.com> wrote:
>
>  - Add write operation to update fuse data bit when PWE bit is on.
>  - Add array, fuse_wo, to store the 'written' status for all bits
>    of OTP to block the write operation.
>
> Signed-off-by: Green Wan <green.wan@sifive.com>
> Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
> ---
>  hw/misc/sifive_u_otp.c         | 30 +++++++++++++++++++++++++++++-
>  include/hw/misc/sifive_u_otp.h |  3 +++
>  2 files changed, 32 insertions(+), 1 deletion(-)
>

I am not sure how you tested this. I wrote a simple U-Boot command to
call U-Boot sifive-otp driver to test the write functionality, but it
failed.

=> misc write otp@10070000 0 80200000 10
=> misc read  otp@10070000 0 80400000 10
=> md 80400000
80400000: ffffffff ffffffff ffffffff ffffffff    ................
80400010: 00000000 00000000 00000000 00000000    ................
80400020: 00000000 00000000 00000000 00000000    ................
80400030: 00000000 00000000 00000000 00000000    ................
80400040: 00000000 00000000 00000000 00000000    ................
80400050: 00000000 00000000 00000000 00000000    ................
80400060: 00000000 00000000 00000000 00000000    ................
80400070: 00000000 00000000 00000000 00000000    ................
80400080: 00000000 00000000 00000000 00000000    ................
80400090: 00000000 00000000 00000000 00000000    ................
804000a0: 00000000 00000000 00000000 00000000    ................
804000b0: 00000000 00000000 00000000 00000000    ................
804000c0: 00000000 00000000 00000000 00000000    ................
804000d0: 00000000 00000000 00000000 00000000    ................
804000e0: 00000000 00000000 00000000 00000000    ................
804000f0: 00000000 00000000 00000000 00000000    ................
=> misc write otp@10070000 0 80200010 10
=> misc read  otp@10070000 0 80400010 10
=> md 80400000
80400000: ffffffff ffffffff ffffffff ffffffff    ................
80400010: ffffffff ffffffff ffffffff ffffffff    ................
80400020: 00000000 00000000 00000000 00000000    ................
80400030: 00000000 00000000 00000000 00000000    ................
80400040: 00000000 00000000 00000000 00000000    ................
80400050: 00000000 00000000 00000000 00000000    ................
80400060: 00000000 00000000 00000000 00000000    ................
80400070: 00000000 00000000 00000000 00000000    ................
80400080: 00000000 00000000 00000000 00000000    ................
80400090: 00000000 00000000 00000000 00000000    ................
804000a0: 00000000 00000000 00000000 00000000    ................
804000b0: 00000000 00000000 00000000 00000000    ................
804000c0: 00000000 00000000 00000000 00000000    ................
804000d0: 00000000 00000000 00000000 00000000    ................
804000e0: 00000000 00000000 00000000 00000000    ................
804000f0: 00000000 00000000 00000000 00000000    ................

But it can read the serial number at offset 0x3f0

=> misc read  otp@10070000 3f0 80400010 10
=> md 80400000
80400000: ffffffff ffffffff ffffffff ffffffff    ................
80400010: 00000001 fffffffe ffffffff ffffffff    ................
80400020: 00000000 00000000 00000000 00000000    ................
80400030: 00000000 00000000 00000000 00000000    ................
80400040: 00000000 00000000 00000000 00000000    ................
80400050: 00000000 00000000 00000000 00000000    ................
80400060: 00000000 00000000 00000000 00000000    ................
80400070: 00000000 00000000 00000000 00000000    ................
80400080: 00000000 00000000 00000000 00000000    ................
80400090: 00000000 00000000 00000000 00000000    ................
804000a0: 00000000 00000000 00000000 00000000    ................
804000b0: 00000000 00000000 00000000 00000000    ................
804000c0: 00000000 00000000 00000000 00000000    ................
804000d0: 00000000 00000000 00000000 00000000    ................
804000e0: 00000000 00000000 00000000 00000000    ................
804000f0: 00000000 00000000 00000000 00000000    ................

Regards,
Bin