On 13/11/18 17:07, Simon Goldschmidt wrote:
On 13.11.2018 17:00, Wolfgang Denk wrote:
Dear Simon,
In message CAAh8qsxB3YNoDruZnmcPvkygc7HXVOcf=PNdA4xRp=PjmQANsw@mail.gmail.com you wrote:
My idea was to let SPL implement a dedicated boot counter/watchdog that detects problems starting U-Boot and using a backup copy if it fails multiple times. Of course you need an SPL on your board to do this. Plus you end up with the same problem for updating SPL, but I'm lucky here that my platform (socfpga gen5) has redundant storage for SPL and implements a startup watchdog mechanism for the SPL.
In other words, you are just adding enough additional complexity to SPL to make it reasonably likely that there will be bugs that need to be fixed later, i. e. you have to update the SPL.
And then?
You are just moving the problem, not solving it.
That's not how I see it. As I see it, I have to implement an upgrade option for SPL. This is partly due to bad design of the socfpga_gen5 platform. But also I have read multiple times on this list that you should use SPL from the same version as U-Boot as they might work combined and U-Boot might depend on SPL to do things that might change over time.
Right. It is not guaranteed that mixing versions works.
So is it really a good idea to upgrade U-Boot without upgrading SPL at the same time?
IMHO it is a bad idea, and it forgets that the bootloader is really SPL + u-boot.img else just u-boot.img. It is also questionable if it makes sense to provide an update mechanism for u-boot when most of critical parts like clocks, DDR initialisation, etc. are in SPL.
It seems to me this would require thorough testing of different version mixes...
Agree, and this becomes a mess.
So given that SPL must be upgradable, how is it more complex to detect U-Boot failure from SPL than from U-Boot itself?
I do not get the question - if SPL fails, it can be at any time before you get the control. There sould be a mechanism to switch to a previous copy of SPL, generally this is not available in hw.
Best regards, Stefano