[U-Boot] [PATCH v2 1/2] Add README for the "Falcon" mode

[Otavio Salvador]

On Wed, Nov 14, 2012 at 10:19 AM, Stefano Babic <sbabic at denx.de> wrote:

> On 14/11/2012 11:29, Otavio Salvador wrote:
> >
>
> Hi Otavio,
>
> >
> > In the text you have the offset to save the image onto a NAND offset so
> > I fail to see how it'd be used for SD-Card.
> >
> > Can you elaborate it a bit?
>
> No, I can't without introducing errors. Current code supports Falcon
> only booting from NAND - I do not think that it is a big thing to use
> another media, but it is not yet done. This document must


So I'd say to drop the SD-Card from the document.


> >     +and can be generalized seen as a way to start an image performing
> >     the minimum
> >     +required initialization. SPL initializes mainly the RAM controller,
> >     and after
> >     +that copies U-Boot image into the memory. The "Falcon" mode extends
> >     this way
> >     +allowing to start the Linux kernel directly from SPL. A new command
> >     is added
> >     +to U-Boot to prepare the parameters that SPL must pass to the
> >     kernel, using
> >     +ATAGS or Device Tree.
> >     +
> >     +Falcon adds a command under U-Boot to reuse all code responsible to
> >     prepare
> >     +the interface with the kernel. In usual U-boot systems, these
> >     parameters are
> >     +generated each time before loading the kernel, passing to Linux the
> >     address
> >     +in memory where the parameters can be read.
> >     +With falcon, this snapshot can be saved into persistent storage and
> >     SPL is
> >     +informed to load it before running the kernel.
> >
> >
> > You mix Falcon and falcon.
>
> You're right, there are already comments about this. This will be fixed
> globally in V3 (I will use Falcon Mode consistently).
>
> > I'd say you always use Falcon as it is the
> > name of the feature so it ought to be in upper case. Another thing,
> > 'With falcon, ' ought to be move to the previous line or have an empty
> > line before it.
>
> Ok
>
> >
> >
> >     +To boot the kernel, these steps under a Falcon-aware U-Boot are
> >     required:
> >     +
> >     +1. Boot the board into U-Boot.
> >     +Use the "spl export" command to generate the kernel parameters area
> >     or the DT.
> >     +U-boot runs as when it boots the kernel, but stops before passing
> >     the control
> >     +to the kernel.
> >     +
> >     +2. Saves the prepared snapshot into persistent media.
> >     +The address where to save it must be configured into board
> >     configuration
> >     +file (CONFIG_CMD_SPL_NAND_OFS for NAND).
> >
> >
> > And for others?
>
> Not yet implemented, patches welcome ! But you are right, there is
> already a patch to use a NOR flash that should flow soon into mainline.
> I will check and add documentation for it. For the orher media, the
> document must be updated together when they will be full supported.
>
>
> >
> >
> >     +3. Boot the board into "Falcon" mode. SPL will load the kernel and
> copy
> >     +the parameters area to the required address.
> >     +
> >     +It is required to implement a custom mechanism to select if SPL
> >     loads U-Boot
> >     +or another image.
> >     +The value of a GPIO is a simple way to operate the selection, as
> >     well as
> >     +reading a character from the SPL console if CONFIG_SPL_CONSOLE is
> set.
> >
> >
> > An empty line before "The value"?
>
> Ok
>
> Best regards,
> Stefano Babic
>
> --
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>



-- 
Otavio Salvador                             O.S. Systems
E-mail: otavio at ossystems.com.br  http://www.ossystems.com.br
Mobile: +55 53 9981-7854              http://projetos.ossystems.com.br