[U-Boot] [PATCH 0/3] Add generic FDT memory bank decoding and gd initialization

[Igor Grinberg]

On 12/11/16 18:47, Nathan Rossi wrote:
> On 12 December 2016 at 01:08, Igor Grinberg <grinberg at compulab.co.il> wrote:
>> Hi Nathan,
>>
>> On 12/11/16 15:58, Nathan Rossi wrote:
>>> This series adds two functions for handling the memory bank decoding and
>>> initialization of global data for use by boards in their dram_init and
>>> dram_init_banksize functions.
>>
>> I might have missed some discussions on this meter,
>> can you please provide the use cases for this?
>> IMO, the bootloader's job is to initialize the DRAM, detect its size, and pass
>> the detected DRAM configuration on to an OS.
> 
> Hi Igor,
> 
> I do not think there have been any discussions on this (at least none
> that I am aware of).
> 
> Some boards (like Zynq and ZynqMP ones) are using
> CONFIG_SYS_SDRAM_SIZE to define the amount of memory that is available
> (since detection is not possible). However with the introduction of
> dtbs for some boards they are also capable of loading the size of
> memory from the embedded/appended dtb (instead of hardcoded). This
> allows for more of the board config to be loaded from the device tree
> instead of from include/configs/*.h. This however is up to the
> individual board to implement in its dram_init* functions.

Thanks for the explanation!
I assume that the key point is "detection is not possible" and therefore
we must rely on a user or a production process to place (append) the correct dtb.
Makes sense to me now and looks like an improvement to the current situation.

> 
> The first patch of the series is only adding some decoding helper
> functions to make this generic between the Zynq and ZynqMP boards as
> well as to allow for any other boards that may want to use the same
> mechanism to get the memory size from the fdt. There is no requirement
> for boards to use these functions.

Can you please next time place a similar explanation in at least the cover
letter. This way, the intent might be understood the first time ;-)
I would also like to see some parts of the above explanation in the functions
documentation (e.g. this allows to improve the DRAM configuration mechanics
on boards that cannot detect its DRAM size/config).

Thanks!

> 
> Regards,
> Nathan
> 
>>
>>>
>>> The series also changes the zynq and zynqmp board implementations to use
>>> these functions to resolve a issue with static variable use.
>>>
>>> Nathan Rossi (3):
>>>   fdt: add memory bank decoding functions for board setup
>>>   ARM: zynq: Replace board specific with generic memory bank decoding
>>>   ARM64: zynqmp: Replace board specific with generic memory bank
>>>     decoding
>>>
>>>  board/xilinx/zynq/board.c    | 112 ++-----------------------------------------
>>>  board/xilinx/zynqmp/zynqmp.c | 112 ++-----------------------------------------
>>>  include/fdtdec.h             |  25 ++++++++++
>>>  lib/fdtdec.c                 |  54 +++++++++++++++++++++
>>>  4 files changed, 85 insertions(+), 218 deletions(-)
>>>
>>
>> --
>> Regards,
>> Igor.
> 

-- 
Regards,
Igor.