[U-Boot] SAMA5D2 xplained SD/eMMC boot

[Marek Vasut]

On 04/25/2016 02:55 AM, Yang, Wenyou wrote:
> Hi Marek,
> 
>> -----Original Message-----
>> From: Marek Vasut [mailto:marex at denx.de]
>> Sent: 2016年4月22日 20:18
>> To: Yang, Wenyou <Wenyou.Yang at atmel.com>
>> Cc: u-boot at lists.denx.de
>> Subject: Re: SAMA5D2 xplained SD/eMMC boot
>>
>> On 04/22/2016 02:54 AM, Yang, Wenyou wrote:
>>> Hi Marek,
>>
>> Hi!
>>
>>>> -----Original Message-----
>>>> From: Marek Vasut [mailto:marex at denx.de]
>>>> Sent: 2016年4月21日 10:59
>>>> To: Yang, Wenyou <Wenyou.Yang at atmel.com>
>>>> Cc: u-boot at lists.denx.de
>>>> Subject: Re: SAMA5D2 xplained SD/eMMC boot
>>>>
>>>> On 04/21/2016 04:46 AM, Yang, Wenyou wrote:
>>>>> Hi,
>>>>
>>>> Hi!
>>>>
>>>> [...]
>>>> pile of unnecessary email headers redacted.
>>>> [...]
>>>>
>>>>>>>>>>>> Hi!
>>>>>>>>>>>>
>>>>>>>>>>>> I've been playing around with latest mainline u-boot on
>>>>>>>>>>>> sama5d2 xplained ultra. I noticed that if I want to boot the
>>>>>>>>>>>> board from SD card (SDHCI1), the board will indeed load the
>>>>>>>>>>>> SPL from it, but SPL will try to load u-boot.img from eMMC
>>>>>>>>>>>> (SDHCI0) and fail, as my eMMC is blank.
>>>>>>>>>>>
>>>>>>>>>>> Yes, there is some issue to load u-boot.img. I found there is
>>>>>>>>>>> something to do on
>>>>>>>>>> sdhci.c.
>>>>>>>>>>>
>>>>>>>>>>> You can try this branch, it should works.
>>>>>>>>>>>
>>>>>>>>>>> https://github.com/linux4sam/u-boot-at91/commits/u-boot-2016.0
>>>>>>>>>>> 3-
>>>>>>>>>>> at
>>>>>>>>>>> 91
>>>>>>>>>>
>>>>>>>>>> I am not interested in using non-mainline stuff. Do you have
>>>>>>>>>> any particular patch/commit which I can refer to ? I do not
>>>>>>>>>> think this has anything to do with sdhci.c driver at all, it
>>>>>>>>>> has to do with detecting the boot device from which SPL was
>>>>>>>>>> started and loading u-boot.img from the same boot device
>>>>>>>>>> instead of always using
>>>> SDHCI0.
>>>>>>>>>
>>>>>>>>> I will test the mainline code. I will let you know when I get something.
>>>>>>>>
>>>>>>>> OK.
>>>>>>>>
>>>>>>>> Does the SoC have any sort of register which lists the current boot
>> device ?
>>>>>>>
>>>>>>> In this SoC, there is not register to list the current boot device.
>>>>>>
>>>>>> And thus, it is not possible to detect at runtime from which device
>>>>>> the SoC booted and thus load u-boot.img from the same device. Correct ?
>>>>>
>>>>> Yes,
>>>>
>>>> Ha, thanks for confirming.
>>>
>>> Sorry, can I correct what I said yesterday?
>>
>> What if I said "no" ? :-)
>>
>>> There is a register to list the boot information exported by ROMCode.
>>>
>>> The boot information is stored in R4 register when the ROMCode jumps to the
>> bootstrap.
>>
>> Ha, so the U-Boot SPL can save the r4 register early in the boot and extract the
>> boot device from it. That's neat. Thanks!
>>
>>> Here is the contents definitions R4 on the SAMA5D2 (improved compared to old
>> MPUs to take care of IOSet features).
>>
>> Is this stuff somewhere in the SAMA5Dx datasheet ? It'd be nice to know/have this
>> information for other SAMA5Dx too (d3 and d4).
> 
> It seems it is not included in the in the SAMA5Dx datasheet.

So where did you get these numbers from ?

> This feature is available since AT91SAM9G45, inclusive d3 and d4.

Oh cool, so the numbers are the same for all these chips ?

Thanks!
Best regards,
Marek Vasut