[U-Boot] [PATCH 12/13] armv7: support rk3066 early back to bootrom in start.S

[Simon Glass]

Hi Pawel,

On 7 June 2017 at 09:37, Paweł Jarosz <paweljarosz3691 at gmail.com> wrote:
> Hi Simon,
>
>
> W dniu 06.06.2017 o 23:10, Simon Glass pisze:
>>
>> Hi Pawel,
>>
>> On 6 June 2017 at 12:53, Paweł Jarosz <paweljarosz3691 at gmail.com> wrote:
>>>
>>> Rockchip bootrom first reads 1KB data from nand at offset 0x10080C00 and
>>> executes it. Then waits for back to bootrom and loads another 32KB to
>>> sram
>>> which also executes. Sdram initialisation code needs to be in one of
>>> these two
>>> steps. Then bootloader loads another ~200KB of data at offset 0x60000000
>>> and jumps to it.
>>>
>>> 32KB of data is a little low for tpl + spl part and ~200KB data is to low
>>> for
>>> u-boot part(for example to boot from mmc you need to disable usb support.
>>>
>>> My solution to size problem is to move sdram initialisation code to tpl
>>> stage,
>>> move spl part to third stage(reading 200KB data) and add support for
>>> loading
>>> u-boot by spl from ext2/4, fat partitions.
>>>
>>> But moving sdram initialisation code to tpl increases size of tpl above
>>> 1KB
>>> (first boot stage). Solution to this is to add code which will be below
>>> 1KB
>>> offset in tpl binary and do back to bootrom at very beginning of the tpl
>>> execution.
>>
>> So do you mean that TPL starts and then loads more of itself? Why not
>> put SDRAM init in SPL? You say above that 32KB is 'too low', but It's
>> not clear why.
>
> Ad.1 No. Tpl starts and at the first execution returns to bootrom. Bootrom
> then loads
> rest of the tpl (31KB) and executes it for a second time.

So can we do this trick with SPL and drop TPL?

>
> Ad.2,3 Due to size issues (200KB limit) i needed to move main u-boot to mmc.
> To load u-boot from
> mmc by SPL (there is 32KB bootrom limit, not enough space for mmc support) i
> moved SPL to sdram.
> Code executed in sdram can't mess with sdram settings because it will hang
> the board. Sdram setup
> needs to be done by code in SRAM (tpl).

You should be able to fit MMC and SDRAM into 32KB. E.g. I can build
firefly-rk3288 that way as Heiko mentions

>
>>> Adding this few lines of code here meets these conditions.
>>>
>>> Signed-off-by: Paweł Jarosz <paweljarosz3691 at gmail.com>
>>> ---
>>>   arch/arm/cpu/armv7/start.S | 13 +++++++++++++
>>>   1 file changed, 13 insertions(+)
>>>
>>> diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
>>> index f06fd28..73e03d9 100644
>>> --- a/arch/arm/cpu/armv7/start.S
>>> +++ b/arch/arm/cpu/armv7/start.S
>>> @@ -36,6 +36,19 @@
>>>   #endif
>>>
>>>   reset:
>>> +
>>> +#if defined(CONFIG_ROCKCHIP_RK3066) && defined(CONFIG_TPL_BUILD)
>>> +       ldr     r3, =0x10080900
>>> +       ldr     r0, [r3]
>>> +       cmp     r0, #1
>>> +       movne   r0, #1
>>> +       strne   r0, [r3]
>>> +       beq     out_of_bootrom
>>> +       bx      lr
>>> +out_of_bootrom:
>>> +       mov     r0, #0
>>> +       str     r0, [r3]
>>> +#endif
>>>          /* Allow the board to save important registers */
>>>          b       save_boot_params
>>>   save_boot_params_ret:
>>> --
>>> 2.7.4

Regards,
Simon