[U-Boot] [PATCH 4/4 v2] xilinx: Add new Zynq board

[Joe Hershberger]

Hi Michal,

On Thu, Aug 16, 2012 at 1:12 AM, Michal Simek <monstr at monstr.eu> wrote:
> Hi Joe,
>
>
> On 08/15/2012 07:31 PM, Joe Hershberger wrote:
>>
>> Hi Michal,
>>
>> I believe this is a fundamental misunderstanding of the Zynq architecture.
>
>
> I don't think that this is not my fundamental misunderstanding.
>
>
>>
>> With the microblaze and virtex ppc architecture you basically have an
>> FPGA that happens to have a processor in it.  The Zynq architecture is
>> the opposite... an ARM system that happens to have an FPGA attached to
>> it.
>
>
> We are working in this area for quite a long time to be convinced that
> this is the best solution we can make. And even this is only one way how
> to maintain this platform. Creating new u-boot board description for every
> board or configuration is bad idea.
>
>
>>
>> The different boards have plenty of hard IP and peripherals available
>> for all of the key interfaces that u-boot needs to be aware of.
>> Certainly there can be other peripherals added to the fabric and those
>> can be handles with device tree.  Generally these boards are well
>> defined, unlike microblaze targets.
>
>
>
> Zynq is not like any other ARM based board. There is still a lot of space
> for configuring it and you need all the time any input from user even
> if you use reference board. All reference boards contains a lot of
> connectors
> which started with FMC, pins, configurable options.

It is possible to add custom features in the fabric.  I agree that it
is not reasonable to support many different possible things there.
That should be left to the user to customize.

On the other hand, I think it should be easy to use a given board
without first learning everything about it.  Please consider each
board as though it has no fabric.  What can be supported on the board
with what is connected to the MIO port?  Can it run u-boot?  Access
memory?  Access Ethernet or USB?  Boot Linux?  In general, the answer
to all these is yes.  However each board has different things
populated.  Different RAM, different types of flash interfaces,
different Ethernet phys, etc.

If I get a Zed board and you get a ZC702 board, we should not each
have to write a DTS file and customize all the other config file
settings when those differences are known based on the board, just
because it is possible to further extend each of these boards beyond
their MIO capabilities.

-Joe