[U-Boot] Problems to Allwinner H3's eFUSE/SID
Hans de Goede
hdegoede at redhat.com
Mon Dec 19 17:27:42 CET 2016
Hi,
On 19-12-16 17:25, Icenowy Zheng wrote:
>
>
> 20.12.2016, 00:17, "Hans de Goede" <hdegoede at redhat.com>:
>> Hi,
>>
>> On 19-12-16 17:06, Icenowy Zheng wrote:
>>> 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.
>>
>> I know, but I think we will just need to accept this onetime change
>> of the fixed MAC addresses to fix this bug. I don't think this is
>> a big problem since the driver for the H3 ethernet has not been
>> merged into the mainline kernel yet.
>>
>>> Maybe we should add #ifdef's to MAC generation code after this fix.
>>
>> I would rather not see #ifdefs for this, see above, but that is no
>> longer my call, see below.
>>
>>> (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.
>>
>> No I'm no longer the maintainer, I'm still the MAINTAINER file because
>> I have a lot of boards and as such I'm still the point of contact for
>> those boards (if there are any board specific issues / questions), but
>> as indicated in the main MAINTAINERS file Jagan Teki <jagan at openedev.com>
>> is the maintainer now.
>
> But the current status of the file will indicates you are the maintainer of boards
> support of sunxi.
No it indicates that I'm the maintainer for the defconfig files for a whole list
of boards, nothing more and nothing less.
If you think it needs to be clarified, feel free to submit a patch to make this
more clear.
Regards,
Hans
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