[RFC PATCH v7 0/2] Add file-backed and write-once features to OTP

[Green Wan]

patch [1/2] - add write function and wrire-once feature
patch [2/2] - add file backend support

Test Steps: (should work even only 1/2 is applied)
 1) Follow instructions to prepare fw_payload - 
https://github.com/riscv/opensbi/blob/master/docs/platform/sifive_fu540.md
    a) build 1-round opensbi
       $ cd opensbi
       $ OBJCOPY=riscv64-buildroot-linux-gnu-objcopy \
       LD=riscv64-buildroot-linux-gnu-ld \
       CC=riscv64-buildroot-linux-gnu-gcc \
       make PLATFORM=sifive/fu540
    b) build u-boot
       # Make sure the 'CONFIG_SIFIVE_OTP=y' is set
       $ cd u-boot
       $ 
OPENSBI=/xxx/opensbi/build/platform/sifive/fu540/firmware/fw_dynamic.bin \
       ARCH=riscv \
       CROSS_COMPILE=riscv64-buildroot-linux-gnu- \
       make
    c) generate fw_payload.elf
       $ cd opensbi
       $ OBJCOPY=riscv64-buildroot-linux-gnu-objcopy \
       LD=riscv64-buildroot-linux-gnu-ld \
       CC=riscv64-buildroot-linux-gnu-gcc \
       make PLATFORM=sifive/fu540 FW_PAYLOAD_PATH=/xxx/u-boot/u-boot.bin
 2) Apply uboot test patch - 
http://patchwork.ozlabs.org/project/uboot/patch/1602657292-82815-1-git-send-email-bmeng.cn@gmail.com/
    Rebuild u-boot and fw_payload.elf
 3) Generate empty otp image. (skip this if only 1/2 is applied.)
    $ dd if=/dev/zero of=./otp.img bs=1k count=16
 4) run qemu with fw_payload.elf
    $ qemu-system-riscv64 -M sifive_u -m 256M -nographic -bios none \
      -kernel ../opensbi/build/platform/sifive/fu540/firmware/fw_payload.elf \
      -d guest_errors -drive if=none,format=raw,file=otp.img 
 5) (uboot otp driver should do some read/write already) Run read/write in 
u-boot

# dump mem before test
=> md 80200000 10
80200000: 84ae822a 00061297 7642b283 10529073    *.........Bvs.R.
80200010: 10401073 031b52c1 13134010 71330153    s.@..R...@..S.3q
80200020: 850a0053 28c0b0ef 812a81aa 00062297    S......(..*.."..
80200030: 94c2b283 a92f4905 16630862 22970209    .....I/.b.c...."
=> md 80400000 10
80400000: 00000000 00000000 00000000 00000000    ................
80400010: 00000000 00000000 00000000 00000000    ................
80400020: 00000000 00000000 00000000 00000000    ................
80400030: 00000000 00000000 00000000 00000000    ................

# check read function and see if serial is set
=> misc read  otp@10070000 3f0 80400000 10
=> md 80400000 10
80400000: 00000001 fffffffe 00000000 00000000    ................
80400010: 00000000 00000000 00000000 00000000    ................
80400020: 00000000 00000000 00000000 00000000    ................
80400030: 00000000 00000000 00000000 00000000    ................

# check write function
=> misc write otp@10070000 0 80200000 10
=> misc read  otp@10070000 0 80400000 10
=> md 80400000 10
80400000: 84ae822a 00061297 7642b283 10529073    *.........Bvs.R.
80400010: 00000000 00000000 00000000 00000000    ................
80400020: 00000000 00000000 00000000 00000000    ................
80400030: 00000000 00000000 00000000 00000000    ................
=>

Changelogs:
v6 to v7:
 - Fix bug in MACRO, SET_FUSEARRAY_BIT.
 - Add serial initialization in sifive_u_otp_reset().
 - revise write-once error message.

v5 to v6:
 - Rebase to latest. (sifive_u_otp.* are moved to hw/misc)
 - Put the example command to commit message.
 - Refine errp handle when check backend drive.
 - Remove unnecessary debug message.

v4 to v5:
 - Change the patch order
 - Add write operation to update pdin to fuse[] bit by bit 
 - Fix wrong protection for offset 0x0~0x38
 - Add SIFIVE_U_OTP_PWE_EN definition
 - Refine access macro for fuse[] and fuse_wo[]

Summary of Patches 
 - First patch is to add write opertion to update pdin data to fuse[] bit
   by bit. Add 'write-once' feature to block second write to same bit of
   the OTP memory.

 - Second patch is to add file-backed implementation to allow users to use
   '-drive' to assign an OTP raw image file. OTP image file must be bigger
   than 16K.

       For example, '-drive if=none,format=raw,file=otp.img'

Testing
 - Tested on sifive_u for both qemu and u-boot.

Green Wan (2):
  hw/misc/sifive_u_otp: Add write function and write-once protection
  hw/misc/sifive_u_otp: Add backend drive support

 hw/misc/sifive_u_otp.c         | 95 +++++++++++++++++++++++++++++++++-
 include/hw/misc/sifive_u_otp.h |  5 ++
 2 files changed, 99 insertions(+), 1 deletion(-)

-- 
2.17.1