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

[Simon Goldschmidt]

On 21.02.2018 15:54, Tom Rini wrote:
> 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 at 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 at denx.de> wrote:
>>>>>>> Dear Sam,
>>>>>>>
>>>>>>> In message
>>>>>>> <CAKaJLVsWKpGeEuS=iZ7QCtZrDfUSA=8GZo3zJDr-VgW-MUCFzA at 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++) {
> ...

Yes, but I think env_get_location() called from env_driver_lookup() 
returns gd->env_load_location for saving...
That seems a little hidden though...

>
>> 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?
>

Something like that, yes.

Simon