[U-Boot] [PATCH v2] sun8i: On H3 Use words 1-3 instead of just word 3 from the SID

[Hans de Goede]

Hi,

On 29-07-16 12:28, Ian Campbell wrote:
> On Fri, 2016-07-29 at 11:49 +0200, Hans de Goede wrote:
>> It seems that bytes 13-14 of the SID / bytes 1-2 from word 3 of the
>> SID
>> are always 0 on H3 making it a poor candidate to use as source for
>> the
>> serialnr / mac-address, and the other non constant words (1 and 2)
>> also
>> have quite a few bits which are the same for some boards,
>>
>> This commits switches to using words 1 - 3 ex-or-ed together to get a
>> more unique value for the mac-address / serialnr.
>>
>> Cc: Chen-Yu Tsai <wens at csie.org>
>> Cc: Corentin LABBE <clabbe.montjoie at gmail.com>
>> Cc: Amit Singh Tomar <amittomer25 at gmail.com>
>> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
>> ---
>> Changes in v2:
>> -ex-or all 3 words together instead of picking a different word
>> ---
>>  board/sunxi/board.c | 15 +++++++++++++++
>>  1 file changed, 15 insertions(+)
>>
>> diff --git a/board/sunxi/board.c b/board/sunxi/board.c
>> index ef3fe26..e0734fb 100644
>> --- a/board/sunxi/board.c
>> +++ b/board/sunxi/board.c
>> @@ -623,6 +623,21 @@ static void setup_environment(const void *fdt)
>>
>>  	ret = sunxi_get_sid(sid);
>>  	if (ret == 0 && sid[0] != 0 && sid[3] != 0) {
>
> Could/should this check be removed now? Or should sid[1]/sid[2] be
> included?

Good point, the check is there because some A10 / A20 boards have an
all 0 sid, now that we make sure that the NIC specific bytes of the
mac are not all 0, only checking for sid[0] != 0 should be enough
to capture non initialized sid-s.

>> +#ifdef CONFIG_MACH_SUN8I_H3
>>> +		/*
>>> +		 * The single words 1 - 3 of the SID have quite a few bits
>>> +		 * which are the same on many models on the H3, so we ex-or
>>> +		 * them together to get a bit more unique value.
>>> +		 *
>>> +		 * Note we only do this on the H3 as we cannot change the
>>> +		 * algorithm on other SoCs since those have been using
>>> +		 * fixed mac-addresses based on only using word 3 for a
>>> +		 * a long time and changing a fixed mac-address with an
>>>> +		 * u-boot update is not good.
>
> I wonder if we should invert this, i.e. make it not use this new method
> on all existing models. That would mean that all future models will
> automatically use this new (IMHO better) scheme instead of requiring it
> to be manually added each time (which we are sure to forget to do).

Good point, I'll fix this and the above check for v3.

Regards,

Hans