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

[Paweł Jarosz]

W dniu 15.06.2017 o 16:50, Simon Glass pisze:
> + Some other rockchip people
>
> Hi Pawel,
>
> On 15 June 2017 at 01:15, Paweł Jarosz <paweljarosz3691 at gmail.com> wrote:
>> Hi Simon
>>
>>
>> W dniu 14.06.2017 o 13:06, Simon Glass pisze:
>>
>> +Philippe
>>
>> Hi Pawel,
>>
>> On 12 June 2017 at 17:50, Simon Glass <sjg at chromium.org> wrote:
>>
>> Hi Pawel,
>>
>> On 9 June 2017 at 06:31, Paweł Jarosz <paweljarosz3691 at gmail.com> wrote:
>>
>> W dniu 09.06.2017 o 13:46, Heiko Stuebner pisze:
>>
>> Am Mittwoch, 7. Juni 2017, 17:37:13 CEST schrieb 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).
>>
>> At least the rk3288-Firefly was able to also have mmc stack in the SPL in
>> the past, without requiring the back_to_bootrom at all. So question would
>> be why this doesn't fit anymore, or on the rk3066 specifically.
>>
>> Also, it seems like I got my hands on a preliminary (linux/mtd) nand
>> driver
>> (rk3228 but cursory glance at the registers suggests that it may actually
>> work on previous socs down to the rk3066 as well) and it may be possible
>> to adapt that for uboot, therefore making the spl able to also load the
>> full u-boot from without needing back_to_bootrom.
>>
>>
>> Heiko
>>
>> I was not able to get mmc support on rk3066 in spl in ~31kb (32kb - 1kb for
>> tpl)size limit.
>> One (or two i didn't check how much) back to bootrom is required on rk3066.
>> If not done bootrom stays in weird state and halts on bringup secondary cpu
>> in kernel. So it's rk3066 specific.
>>
>> What size do you get? With firefly-rk3288 I get about 25KB with SDRAM
>> init and MMC stack. Are you building with Thumb 2?
>>
>> If you are on irc we could try to clear this up more quicky (I am sjg1)
>>
>> To summarise where I think we got to:
>>
>> - move DRAM init into SPL
>> - either have a very small TPL which just returns to boot ROM, or
>> adjust start.S to return to the boot room early in SPL to load the
>> other 31KB
>>
>> Can you please post to the mailing list with your thoughts on this so
>> that others (including rockchip) can chime in? I think either will
>> work but I think others will have an opinion.
>>
>> Regards,
>> Simon
>>
>>
>> About moving dram init to spl i agree.
>>
>> I think early back to bootrom in start.S is a good solution as it would give
>> me 1KB more space for spl and i could drop hacks like jumping to spl in tpl
>> board file. But I would like to hear the opinion of other people on this.
> So with this solution there would be no TPL needed? It sounds
> reasonable to me. I'd like to hear other opinions also.

We don't need tpl if i use early back to bootrom in start.S patch with 
spl... but i didn't test it yet. If it will work i will drop the tpl. Is 
that ok?

>> Also i got a nandc driver from Heiko and i would like to adopt it for u-boot
>> in the next version. Is it ok?
> Sounds good.
>
> Regards,
> Simon