On 02/20/2017 03:07 PM, Dalon Westergreen wrote: [...] >>> Okay, after much discussion and debate with a colleague..\ >>> >>> Warm reset is preferred as the bootrom keeps a score card to determine >>> whether an spl image in the boot media failed or not. If it failed, >>> on a warm reset it will not retry the failed image. >> >> So what will it do ? Try a valid image from another slot at offset >> +n*64kiB ? > > Yes. Or when the scorecard indicates 4 failures it will just stop.
I see. >>> >>> The other reason warm resets are preferred is for preservation of the >>> dram contents. On a warm reset it is possible to skip io configuration >>> and dram calibration so that the contents can be saved. >> >> That's a good point. >> >> But here's a counterargument, what if you upgrade U-Boot ? Warm reset >> will use the old SPL and the system will likely hang upon reboot ;-) >> >>> >>>> >>>> How do you point bootrom to run that snippet instead of whatever is in >>>> the OCRAM ? >>>> >>> >>> This code here >>> >>>> >>>> > > > > > > + writel(ramboot_addr, >>>> > > > > > > + &sysmgr_regs- >>>> > > > > > > >romcodegrp_warmramgrp_execution); >> >> Can't you just feed a function pointer pointing into some function which >> is part of the SPL into that register then ? I think that'd do the same >> trick, no ? > > Yes, you could, but the idea of putting the code at the end of memory is to > allow the onchip ram to be used for other things. Well if you corrupt SPL and do a warm-reset, your system won't boot. We had that already (and that's another +1 for just doing cold reset, always). >>> >>> writes the address to jump to on warm reset. The register value >>> is preserved through a warm reset. >> >> That's neat, I didn't know that. >> >>> >>>> >>>> >>> >>> All that said, i frankly do not believe for the CSEL=0 case >>> there is any merit to doing the above. Although it "preserves" >>> the behaviour as compared to other CSEL values, i think a much >>> simpler method is to, for the CSEL=0 case, just issue a cold reset. >>> >>> As in this case we are touching the clocks, i am not sure the >>> use cases for a warm reset even hold (sdram preservation, etc). >>> So i agree with you, and suggest only enabling the warm reset >>> for cases where CSEL != 0. >>> >>> Unless there are objections, I will do just that and resubmit a >>> patch. (which should now be just a few lines of code) >> >> See above, if this actually fixes issue, let's get it in. But in a >> civilized fashion, no random ad-hoc asm if possible please :) > > In v3 i just used the simpler method of not allowing warm resets for > csel=0. This is far cleaner, and likely more reliable. Hm, OK, it's fine either way for me. -- Best regards, Marek Vasut _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
