[U-Boot] [linux-sunxi] Re: [PATCH 0/7] ARM: sunxi: Add basic support for Allwinner A31 (sun6i)

[Chen-Yu Tsai]

Hi,

On Thu, Sep 18, 2014 at 4:31 PM, Hans de Goede <hdegoede at redhat.com> wrote:
> Hi,
>
> On 09/18/2014 06:27 AM, Siarhei Siamashka wrote:
>> On Tue, 09 Sep 2014 09:00:57 +0200
>> Hans de Goede <hdegoede at redhat.com> wrote:
>>
>>> Hi,
>>>
>>> On 09/08/2014 03:28 PM, Chen-Yu Tsai wrote:
>>>> Hi everyone,
>>>>
>>>> This series add basic support for Allwinner's A31 SoC. The patches,
>>>> excluding the first one, were cherry-picked from u-boot-sunxi. Due to
>>>> the difference between u-boot mainline and u-boot-sunxi, some patches
>>>> were rearranged or squashed to better fit the current state of u-boot,
>>>> and not introduce any build breaks. It follows Ian's initial merge
>>>> method of sun7i support: introducing various components first, then
>>>> enabling them in the last commit. I tried to keep the commits separate,
>>>> thus retaining the original author and Signed-off-bys.
>>>>
>>>> Patch 1 adds a wrapper around "func(USB, usb, 0)" in BOOT_TARGET_DEVICES
>>>> to deal with breakage when USB support is not enabled.
>>>>
>>>> Patch 2 adds memory addresses for some hardware blocks new in sun6i.
>>>>
>>>> Patch 3 adds support for the new PRCM (power reset and clock management)
>>>> block, which also contains PLL bias voltage control.
>>>>
>>>> Patch 4 adds support for the clock module. This patch is a bunch of
>>>> different sun6i related patches on the clock code, from when sun6i
>>>> support was introduced to u-boot-sunxi, up to its current form.
>>>> This is done to avoid various conflicts and needlessly introducing
>>>> then removing macros.
>>>>
>>>> Patch 5 adds mmc support on sun6i.
>>>>
>>>> Patch 6 adds uart0 muxing on sun6i.
>>>>
>>>> Patch 7 enables sun6i support and adds defconfig for the Colombus board.
>>>
>>> Chen,
>>>
>>> Many thanks for working on this!
>>>
>>> Just a quick not for people celebrating too early, this is the *incomplete*
>>> sun7i support from the linux-sunxi/u-boot-sunxi git repo. It is fine to
>>> merge this upstream, but this does not include SPL support.
>>>
>>> This allows replacing u-boot.bin on allwinnner sd-card images, which is
>>> very useful. But it does not get us all the way to booting sun7i devices
>>> we still need boot0 and boot1 binaries from allwinner for that (for now).
>>
>> If I understand it correctly, one of the things that needs to be done
>> in SPL is the initialization of the DRAM controller. A few weeks ago
>> Oliver has updated the http://linux-sunxi.org/DRAM_Controller page
>> and added a link to the 'dram_sun6i.c' file from the rhombus-tech.net
>> u-boot repository:
>>     http://git.rhombus-tech.net/?p=u-boot.git;a=blob;f=arch/arm/cpu/armv7/sunxi/dram_sun6i.c;hb=refs/heads/allwinner-sunxi-a31
>> Does this repository look like exactly the missing part of code?
>
> Yes it does, interesting. I had found that file before, but this one
> was missing in the repo I found then:
>
> http://git.rhombus-tech.net/?p=u-boot.git;a=blob;f=arch/arm/include/asm/arch-sunxi/dram.h;hb=refs/heads/allwinner-sunxi-a31
>
> But with that one added, this is definitely interesting.

The A31 Hummingbird's SDK has provided us with full boot0/boot1,
which also includes the dram code:

http://dl.linux-sunxi.org/SDK/A31/unpacked-stripped/a31_v4.5_hummingbird_kfb_ok/lichee/boot-v1.0/boot/source/init_dram/

It is more complex than what we found in u-boot.
This code also shows what is encoded into the dram parameters
found in the fex files.

>> Assuming that this code works, it provides a usable starting point
>> for us.
>
> Yep, assuming :) If no one beats me to it I'll take a look at this as
> time permits.
>
>> It looks like the Allwinner A31 DRAM controller registers are very
>> similar to what is used in RK3288 (I have not checked the details,
>> but if we are very lucky, it might be even a 100% perfect match):
>>     https://chromium-review.googlesource.com/#/c/209419/
>> And thanks to the Rockchip developers (who are contributing this
>> DRAM controller support code to coreboot), now we have a lot of
>> named defines for the individual bitfields in the hardware
>> registers. So we can decode the magic constants used in the
>> Allwinner code. And thanks to Texas Instruments, we also have
>> some useful documentation, which also happens to be a reasonably
>> good match:
>>     http://www.ti.com/lit/ug/spruhn7a/spruhn7a.pdf
>
> Sounds good / useful.
>
>> In general, if we are on our own, then we just need to do all the
>> boring work again (similar to what we did with the Allwinner
>> A10/A13/A20 DRAM controller earlier). Starting with the creation of the
>>     http://linux-sunxi.org/A31_DRAM_Controller_Register_Guide
>> wiki page and populating it with the information gathered from the
>> Allwinner and Rockchip source code and also from the TI Keystone2
>> documentation. Naturally, every bit of this information needs to
>> be verified on real Allwinner A31 hardware before we can make any
>> assumptions.
>
> Yep.

Matching the register bits with the parts decoded from dram
parameters seems like a place to start, though i don't understand
much of the terminology.

>> However Allwinner has promised to provide us with some better
>> documentation later this month:
>>     https://www.mail-archive.com/linux-sunxi@googlegroups.com/msg06840.html
>> I don't know if they are going to include the documentation for the
>> DRAM controller in the first new documentation delivery. It surely
>> may be complicated, because Allwinner is obviously licensing the DRAM
>> controller IP from a third party and not designing it from scratch
>> (in a nice company with Rockchip and Texas Instruments). But Texas
>> Instruments somehow can provide the DRAM controller documentation
>> in free public access. So I would guess that it should be possible
>> for Allwinner too.
>>
>> We still need proper Power-Down and Self-Refresh mode support for
>> Allwinner A10/A13/A20. And I had plans to do some investigation for
>> this stuff. But now this activity is temporarily suspended until
>> we see what kind of assistance Allwinner is going to provide to us
>> (A usable DRAM controller documentation? A contribution of DRAM
>> code for u-boot? Nothing?).

Cheers
ChenYu