[U-Boot] SAMA5D2 xplained SD/eMMC boot

[Yang, Wenyou]

> -----Original Message-----
> From: Marek Vasut [mailto:marex at denx.de]
> Sent: 2016年4月25日 18:30
> To: Yang, Wenyou <Wenyou.Yang at atmel.com>
> Cc: u-boot at lists.denx.de
> Subject: Re: SAMA5D2 xplained SD/eMMC boot
> 
> 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 ?

Yes, it is not included in the datasheet now. We are not recommend to use them.

If it is helpful for you,  please reference the previous mail.

> 
> > This feature is available since AT91SAM9G45, inclusive d3 and d4.
> 
> Oh cool, so the numbers are the same for all these chips ?

Yes, basically same, only d2 includes additional ioset information.


Best Regards,
Wenyou Yang