[U-Boot] [RFC] Make U-Boot log great again

[Tom Rini <trini@konsulko.com>]

On Wed, Feb 21, 2018 at 03:38:42PM +0100, Simon Goldschmidt wrote:
> On 21.02.2018 14:35, Tom Rini wrote:
> >On Tue, Feb 20, 2018 at 10:59:33AM +0100, Lukasz Majewski wrote:
> >>On Tue, 20 Feb 2018 09:00:56 +0100
> >>Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> >>
> >>>On Mon, Feb 19, 2018 at 07:47:52PM +0200, Sam Protsenko wrote:
> >>>>On 18 February 2018 at 23:22, Wolfgang Denk <wd@denx.de> wrote:
> >>>>>Dear Sam,
> >>>>>
> >>>>>In message
> >>>>><CAKaJLVsWKpGeEuS=iZ7QCtZrDfUSA=8GZo3zJDr-VgW-MUCFzA@mail.gmail.com>
> >>>>>you wrote:
> >>>>>>Right now U-Boot and SPL logs are cluttered with bogus warnings
> >>>>>>like these (on X15 board, but I'm pretty sure it should appear
> >>>>>>on many others):
> >>>>>>
> >>>>>>     Loading Environment from FAT...
> >>>>>>     *** Warning - bad CRC, using default environment
> >>>>>I donpt want to question the purpose of your patch series in
> >>>>>genral, but:
> >>>>Oh, it's merely a discussion, not a patch series. I probably
> >>>>shouldn't have been added that RFC tag, it's confusing, sorry.
> >>>>>This is NOT a bogus warning - actually it is something which is
> >>>>>not supposed to happen on any sane system.  If it does on your
> >>>>>board even after first boot and running "env save" at least once,
> >>>>>then you have some problem either in the design or implementation
> >>>>>of your board code.
> >>>>>
> >>>>>So this is a very valid warning which means: FIX ME!
> >>>>AFAIU, that behavior was changed in the mentioned patch (please see
> >>>>my original message). Let me elaborate a bit. In v2018.01 everything
> >>>>works fine and none errors/warnings are present on my boards (AM57x
> >>>>EVM and X15 board). The problem appears after commit fb69464eae1e
> >>>>("env: Allow to build multiple environments in Kconfig"). Now U-Boot
> >>>>tries to load the environment from SD card first (uEnv.txt file on
> >>>>FAT partition), and then from eMMC partition. In case when SD card
> >>>>is not inserted, I observe mentioned errors. So I'm not sure how to
> >>>>handle this properly, that's why I created this thread... Let me
> >>>>try and explain my concerns better:
> >>>>  1. On the one hand, it's good to check the environment on both SD
> >>>>card and eMMC (that was done in mentioned patch). This case seems to
> >>>>be legit (at least as far as I understand it), i.e. when SD card is
> >>>>not inserted, it's fine, we just check the env on eMMC
> >>>>  2. But on the other hand, errors shouldn't appear in boot log, if
> >>>>it's legit case, it's confusing the user
> >>>That patch intent was to keep the current behaviour as is for all
> >>>users, so the fact that you now have the FAT environment enabled is an
> >>>unwanted side-effect.
> >>The same situation is on Beagle Bone Black. Even though with OE it is
> >>built to use eMMC for storing its envs, by default it also has envs in
> >>FAT support enabled.
> >>
> >>For that reason, u-boot on this board looks for envs in FAT first and
> >>similar message is printed.
> >>
> >>IMHO, we now have (unintentionally) the situation where implicitly
> >>reading envs from FAT has the highest priority.
> >It's not so much unintentional but rather that the mechanism to define
> >the priority order isn't being provided specifically by
> >board/ti/am335x/board.c so we get the default order.
> >
> >And one thing that I think does need to happen now is that the error
> >messages about "didn't find valid environment in ..." need to be
> >rethought a bit.  It would probably also make sense to move from every
> >env operation tries every possible env location to env init finds the
> >first valid location, tells the user clearly it's using that, and then
> >always uses it.
> 
> But it's like that already, isnt' it? Env load selects the first valid
> location in the list and env save uses that location. All other env
> operations work on the environment in memory.

For saveenv we have:
for (prio = 0; (drv = env_driver_lookup(ENVOP_SAVE, prio)); prio++) {
...

> Also, for transitioning e.g. from MMC to FAT, we would need a mechanism to
> store to an environment place other than the one selected at load time.

Ah, so we have different valid use cases.  Maybe a new env sub-command,
switch?

-- 
Tom
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