[U-Boot] [PATCH v3 1/4] mips: add base support for atheros ath79 based SOCs

[Daniel Schwierzeck]

Am 27.12.2015 um 12:04 schrieb Marek Vasut:
> On Sunday, December 27, 2015 at 11:18:25 AM, Wills Wang wrote:
>> On 12/27/2015 06:09 PM, Marek Vasut wrote:
>>> On Sunday, December 27, 2015 at 09:07:36 AM, Wills Wang wrote:
>>>> On 12/27/2015 03:38 PM, Marek Vasut wrote:
>>>>> On Sunday, December 27, 2015 at 08:33:26 AM, Wills Wang wrote:
>>>>>> On 12/27/2015 02:37 AM, Marek Vasut wrote:
>>>>>>> On Saturday, December 26, 2015 at 07:29:51 PM, Wills Wang wrote:
>>>>>>>> WASP is ar9341.
>>>>>>>
>>>>>>> Please do not top post.
>>>>>>>
>>>>>>> Did you try if the memory is accessible on your platform ? AR9331 I
>>>>>>> have here has the SRAM at 0xbd007000 , just like that machine in [1]
>>>>>>> .
>>>>>>
>>>>>> I found there is a memory segment at 0xbd000000...0xbd007fff. it's
>>>>>> independent of DDR physical memory, can be read and wrote, but
>>>>>> hardware can't boot up if don't execute lowlevel_init.S when define
>>>>>> CONFIG_SYS_INIT_SP_ADDR=0xbd007000 to set C stack into SRAM.
>>>>>
>>>>> Stack grows down, so of course if you put stack at the beginning of
>>>>> SRAM, that cannot work ;-) Put it at the end , 0xbd008000.
>>>>
>>>> This memory segment was mapped circularly at 0xbd000000...0xbdffffff.
>>>
>>> So is this area at 0xbd008000 usable for stack or not ?
>>
>> Same times board can boot up, but in a very unstable. i use the
>> following setting:
>>
>> #define CONFIG_SYS_INIT_RAM_ADDR    0xbd000000
> 
> Should be 0xbd007000
> 
>> #define CONFIG_SYS_INIT_RAM_SIZE    (32 * SZ_1K)
> 
> Should be 4 KiB large.
> 
>> #define CONFIG_SYS_INIT_SP_OFFSET \
>>      (CONFIG_SYS_INIT_RAM_SIZE - GENERATED_GBL_DATA_SIZE)
>> #define CONFIG_SYS_INIT_SP_ADDR \
>>      (CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_INIT_SP_OFFSET)
> 
> Did you investigate why the board has problems ?
> 

according to the description above by Wills those three defines setup
the values correctly for start.S:

#define CONFIG_SYS_INIT_RAM_ADDR    0xbd000000
#define CONFIG_SYS_INIT_RAM_SIZE    (32 * SZ_1K)
#define CONFIG_SYS_INIT_SP_ADDR \
        (CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_INIT_RAM_SIZE)

The stack pointer will then be set to the end of the SRAM area with a 16
Byte alignment. The resulting address should be 0xbd007ff0. From this
address, the size of gd_t and CONFIG_SYS_MALLOC_F_LEN will be
subtracted. The remaining space is available for the initial stack.

Which value did you chose for CONFIG_SYS_MALLOC_F_LEN? It must be big
enough to satisfy all malloc requests by the DM stack and small enough
to fit in 32k minus stack size and gd_t size.

Important note: do net set CONFIG_SKIP_LOWLEVEL_INIT yet because that
leaves you without initialized RAM or caches. If the setup does not work
yet, you likely need to init some extra bits to make the SRAM working.

-- 
- Daniel