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

[Marek Vasut]

On 12/29/2016 04:26 PM, Tom Rini wrote:
> 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?

This is adding code complexity, but this is not my point.

> 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!".

Well, this doesn't answer my question, because if I understand this
patch correctly, it copies the entire legacy image (incl. header) into
RAM instead of copying just the image payload (which we already do). I
don't really understand why we want to do this. Or do I misunderstand
something ?

-- 
Best regards,
Marek Vasut