[U-Boot] [RFC PATCH 4/4 v3] mtd: sf: Add CONFIG_SPI_N25Q256A_RESET for software-reset

[Stefan Roese <sr@denx.de>]

On 02.10.2014 01:07, Pavel Machek wrote:
> On Wed 2014-10-01 21:25:12, Stefan Roese wrote:
>> On 01.10.2014 21:04, Jagan Teki wrote:
>>>>>> This is needed for the SoCFPGA booting from SPI NOR flash
>>>>>> e.g. (N25Q256A). With these changes, the SoCrates can boot and
>>>>>> re-boot (reset) from SPI NOR flash without any problems.
>>>>>
>>>>>
>>>>> Seems like your SPI NOR reset logic is buggy. Does any of [1] apply to
>>>>> your
>>>>> board please?
>>>>>
>>>>> [1] http://www.rocketboards.org/foswiki/Documentation/SocBoardQspiBoot
>>>>
>>>>
>>>> Yes. This seems to be that case. But I can't change it right now. So this
>>>> "solution" with the soft-reset is better than nothing.
>>>
>>> If this is some think that must require, any possibility to this
>>> resetting prior to u-boot?
>>> like preloader or in first stage boot loader or something.
>>
>> Perhaps I was not clear with the intention of this patch. Its more to show
>> how the problem with SPI flash on this platform / board (SoCrates in this
>> case) can be solved. So that others have a reference. Thats why I marked it
>> as RFC. Its not really meant for inclusion into mainline.
>>
>> The real solution is a board rework. If not possible, the preloader should
>> be changed. As I don't have access to the preloader code right now, this
>> "solution" (I know, its more a hack) didn't seem too bad.
>
> For the record, I do not think preloader is good place for such
> workaround. Preloader works with SDRAM, and should load real u-boot as
> fast as possible. If it does not need to touch SPI (it does not,
> right?) it should not need to work around bugs there.

In this case, where the board boots from SPI NOR flash, the Preloader 
(SPL U-Boot version) does use SPI. To load the main U-Boot image from 
the SPI NOR flash.

My current best guess is that this define in the Preloader (older SPL 
U-Boot version) causes these problems:

#define CONFIG_SPI_FLASH_QUAD		(1)

Once I have full access to the Preloader source (in a few days 
hopefully) I can verify this.

Thanks,
Stefan