[U-Boot] [RFC PATCH 1/5] spl: dfu: add dfu support in SPL

[Lukasz Majewski <l.majewski@samsung.com>]

Hi Ravi,

> Hi Lukasz
> 
> >> 
> >> >My point here is to first load SPL u-boot (which size is around
> >> >110 KiB), and then download via DFU full-featured u-boot, which
> >> >would be placed in SDRAM.
> >> 
> >> Yes this is good idea, so the SPL-DFU will have only RAM device 
> >> support (to load u-boot into DDR). But we don't have DFU command
> >> to jump to u-boot after loading u-boot into DDR.
> 
> >I think that we don't need dfu command in SPL to boot fully-featured
> >u-boot.
> 
> >Lets consider following scenario:
> 
> >- ROM bootloader (IPL) fetches SPL u-boot via USB. Then it passes
> >  execution to it.
> >- The running SPL downloads fully-fledged u-boot [*] to RAM and
> >passes
> >  execution to it (as it is done in board_init_r
> > @ ./common/spl/spl.c). There is no need for any special command(s)
> > to do that.
> >- Fully-blown u-boot flashes all needed images and reboots the board.
> >- Now the board is setup with proper u-boot, kernel and rootfs
> 
> > [*] - This version of u-boot only requires to have hardcoded
> > "bootcmd"
> >env variable. It would consist the list of commands needed for
> >flashing your target board. The "dfu_alt_info" should be hardcoded
> >as well.
> 
> 
> >> The DFU basically just
> >> download firmware to memory devices like mmc/sd/eMMC/RAM.
> >> So the
> >> question is how to transfer control to u-boot after downloading
> >> the u-boot to DDR using SPL-DFU/RAM.
> 
> > Please consult board_init_r function at ./common/spl/spl.c
>  
> Yes, this is common u-boot flow, make sense, I was thinking exiting
> from DFU loop, user has to press Ctrl+C to exit from DFU after
> download of u-boot to IRAM. 

It is not needed to press Ctrl+C to exit the loop.

Please try dfu-util -e -a0 -D <your_image>

The '-e' switch allows to exit the loop and go into the prompt.

Moreover, your can also try out the '-R' switch, which would impose
board reset after successful dfu flashing.


> We can leverage the existing DFU/RAM
> support.  Main concern is SPL+DFU size. I will rework and come back
> on how much size can be reduced.

Great.

> 
> Thanks Lukasz for great support. 

No problem :-)

> 
> Regards
> Ravi
> 



-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group