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

[Hans de Goede]

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.

> 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.

> 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?).

Regards,

Hans