[U-Boot] [PATCH] SPL: NOR: Add CONFIG_SPL_NOR_COPY_ENTIRE_IMAGE define to enable whole image copy from NOR

[Tom Rini]

On Thu, Dec 29, 2016 at 12:41:06AM +0100, Marek Vasut wrote:
> On 12/28/2016 09:52 AM, Lukasz Majewski wrote:
> > Hi Marek,
> > 
> >> On 12/26/2016 05:36 PM, Lukasz Majewski wrote:
> >>> Hi Marek,
> >>>
> >>>> On 11/29/2016 07:18 PM, Tom Rini wrote:
> >>>>> On Tue, Nov 29, 2016 at 11:50:34AM +0100, Marek Vasut wrote:
> >>>>>> On 11/29/2016 10:11 AM, Lukasz Majewski wrote:
> >>>>>>> Hi Marek,
> >>>>>>>
> >>>>>>>> On 11/28/2016 10:09 PM, Lukasz Majewski wrote:
> >>>>>>>>> This define gives the possibility to copy entire image
> >>>>>>>>> (including header - e.g. u-boot.img) from NOR parallel memory
> >>>>>>>>> to e.g. SDRAM. The current code only supports loading the raw
> >>>>>>>>> binary image (the u-boot.bin).
> >>>>>>>>>
> >>>>>>>>> The legacy behavior is preserved, since other board don't
> >>>>>>>>> enabled this option.
> >>>>>>>>
> >>>>>>>> Sooooo, what's the usecase again ? ;-) 
> >>>>>>>
> >>>>>>> :-)
> >>>>>>>
> >>>>>>> The use case is to allow u-boot.img being loaded from Parallel
> >>>>>>> NOR. The current code only supports u-boot.bin.
> >>>>>>
> >>>>>> Why is u-boot.bin (or the payload) not sufficient ? Why do you
> >>>>>> need the header ?
> >>>>>
> >>>>> Well, the general use-case and code flow is that we load
> >>>>> u-boot.img (or a FIT image) and if all else fails, fall back to
> >>>>> assuming a .bin and a known address).
> >>>>>
> >>>> And exactly how is that whole image useful in RAM ? Sorry, I still
> >>>> do not see it, usually you just need the executable payload,
> >>>> although even that can be left in flash most of the time.
> >>>
> >>> The use case is that I do want to boot from SD card/eMMC and NOR
> >>> with using u-boot.img.
> >>>
> >>> I would like to avoid situation when for NOR I must use u-boot.bin
> >>> and for eMMC u-boot.img.
> >>>
> >>> Such approach keeps things as simple as possible :-)
> >>
> >> Oh, so it allows you to detect bitrot for the content in SPI NOR ?
> > 
> > I do not use SPI NOR, it is parallel NOR.
> 
> Sorry, I meant parallel NOR of course.
> 
> >> It's a bit strange we had to use u-boot.bin with SPL there.
> >>
> > 
> > This is how the legacy system behaves. It uses (by default) Parallel
> > NOR for booting (with advised/provided NOR memory timings). After doing
> > some measurements, it turned out that for "tunned" u-boot/SPL there
> > would be the best way to copy it to ram and execute it from there (just
> > like eMMC).
> > 
> > Hence, I would like to use u-boot.img in both booting scenarios.
> 
> I think I was mistaken yesterday, I don't think I understand why copying
> the image including the header into RAM has any benefit compared to
> copying just the image payload to RAM (and yes, we're
> getting back to my original question).

Code complexity and forward compatibility?  The general case in the SPL
framework is that we have either a "legacy" image or a FIT image and we
fall back to "well, just run it!".

-- 
Tom
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