Problems to Allwinner H3's eFUSE/SID

[Icenowy Zheng]

19.12.2016, 23:30, "Hans de Goede" <hdegoede at redhat.com>:
> Hi,
>
> On 19-12-16 16:22, Icenowy Zheng wrote:
>>  Hi everyone,
>>
>>  Today, I and KotCzarny on IRC of linux-sunxi found a problem in the SID
>>  controller of H3 (incl. H2+).
>>
>>  See https://irclog.whitequark.org/linux-sunxi/2016-12-19 .
>>
>>  Two read method of the H3 eFUSE is used in the BSP: by register accessing, or
>>  directly access 0x01c14200.
>>
>>  From http://linux-sunxi.org/SID_Register_Guide we can see a difference between
>>  the H3 SIDs read out by sunxi-fel and the H3 SIDs read out by devmem2 (in
>>  legacy kernel).
>>
>>  According to the source of H2+ BSP[1], H2+ and H3 can be differed by the last
>>  byte of the first word of SID. (0x42 and 0x83 is H2+, 0x00 and 0x81 is H3,
>>  0x58 is H3D (currently not known SoC) )
>>
>>  However, all the SIDs retrieved by `sunxi-fel sid`, both H2+ and H3, start
>>  with 0x02004620, which do not match this rule.
>>
>>  The readout by devmem2 is satisfying this rule: their first word is
>>  0x02c00081, matches H3.
>>
>>  Then I found the SID-reading code from BSP U-Boot[2], which is based on
>>  register operations. With this kind of code (I wrote one prototype in
>>  userspace with /dev/mem), I got "02c00081 74004620 50358720 3c27048e" on
>>  my Orange Pi One. ("02004620 74358720 5027048e 3c0000c3" with sunxi-fel sid)
>>  And, after accessing to the SID by registers, the value of *0x01c14200 become
>>  also "02c00081".
>>
>>  With direct access to 0x01c14200 after boot with mainline kernel, I got also
>>  "02004620".
>>
>>  Then I altered the program to do the register operations with sunxi-fel, the
>>  result is also "02c00081", and changed `sunxi-fel sid` result to "02c00081".
>>
>>  Summary:
>>
>>  +-----------------------------------------------+----------------+
>>  | Read situation | The first word |
>>  +-----------------------------------------------+----------------+
>>  | Direct read by sunxi-fel | 02004620 |
>>  | Direct read in mainline /dev/mem | 02004620 |
>>  | Direct read in legacy /dev/mem | 02c00081 |
>>  | Register access in FEL | 02c00081 |
>>  | Register access in mainline | 02c00081 |
>>  | Direct read after register access in FEL | 02c00081 |
>>  | Direct read after register access in mainline | 02c00081 |
>>  +-----------------------------------------------+----------------+
>>
>>  According to some facts:
>>  - The register based access to SID is weird: it needs ~5 register
>>    operations per word of SID.
>>  - Reading via register access will change the value when reading by accessing
>>    0x01c14200.
>>  - In the u-boot code[2] there's some functions which read out the SID by
>>    registers and then abandoned the value.
>>  - This mismatch do not exist on A64.
>>
>>  I think that: Allwinner designed a "cache" to the SID to make the simplify the
>>  code to read it, and it automatically loaded the cache when booting; however,
>>  when doing first cache on H3, some byte shifts occured, and the value become
>>  wrong. A manual read on H3 can make the cache right again. This is a silicon
>>  bug, and fixed in A64.
>>
>>  This raises a problem: currently many systems has used the misread SID value to
>>  generated lots of MAC addresses, and workaround this SID bug will change them.
>>
>>  However, if this bug is not workarounded, the sun8i-ths driver won't work well
>>  (as some calibartion value lies in eFUSE). I think some early user of this
>>  driver has already experienced bad readout value.
>>  (The calibration value differs on my opi1 and KotCzarny's opipc)
>>
>>  And many wrong SID values have been generated by `sunxi-fel sid`. (Although I
>>  think sunxi-fel must have the workaround)
>>
>>  Note: in this email, "SID" and "eFUSE" both indicate the controller on H3/A64
>>  at 0x01c14000, which is a OTP memory implemented by eFUSE technique.
>>
>>  Furthermore, A83T may also have this problem, testers are welcome!
>>
>>  [1] http://filez.zoobab.com/allwinner/h2/201609022/lichee/linux-3.4/arch/arm/mach-sunxi/sun8i.c
>>  [2] http://filez.zoobab.com/allwinner/h2/201609022/lichee/brandy/u-boot-2011.09/arch/arm/cpu/armv7/sun8iw7/efuse.c
>>
>>  Experiments:
>>  - https://gist.github.com/Icenowy/2f4859ab1bc05814522fc7445179a8c9
>>    A SID readout shell script via FEL with register access.
>>  - https://31.135.195.151:20281/d/efuse/
>>    A SID readout program via /dev/mem with register access by KotCzarny.
>>    (with statically compiled binary)
>
> Good detective work!
>
> I believe this would best be fixed by making u-boot use the register access
> method to get the SID on affected chips, and make sure u-boot reads the
> SID at-least once.

Yes.

However, what I considered is that fixing this bug will change H3 devices'
MAC addresses, as they are derived from SID.

Maybe we should add #ifdef's to MAC generation code after this fix.

(This is why I will create this discussion)

P.S. Are you still the maintainer of sunxi boards support of u-boot? The
MAINTAINER file in board/sunxi indicates this.

I've sent out a new board support several days ago (Orange Pi Zero), and got
one "Reviewd-By". Could you look at it?


>
> Can you write a patch for this ?
>
> Regards,
>
> Hans