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

[Paweł Jarosz]

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.

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).
>> 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
Regards,
Paweł