[U-Boot] A command to discard saved environments?

[U-Boot] A command to discard saved environments?

[Masahiro Yamada]

Hi.


I am looking for a command
that discards the saved environments,
and takes me back to the
"*** Warning - bad CRC, using default environment" state.


In my case, the environment data is saved
at sector 0x400 of the MMC device on my board.


So, I can just do

 > mmc erase 400 10


But, beforehand, I need to know

CONFIG_ENV_IS_IN_MMC
CONFIG_ENV_OFFSET     0x80000

in order to confirm if the above command is doing the right thing.
(If I make a mistake in calculating the offset value,
other data would be damaged.)



Is there a nice command to do that?



-- 
Best Regards
Masahiro Yamada

[U-Boot] A command to discard saved environments?

[Fabio Estevam]

On Wed, Aug 3, 2016 at 12:31 AM, Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
> Hi.
>
>
> I am looking for a command
> that discards the saved environments,

Does this command help?

=> env default -f -a

Regards,

Fabio Estevam

[U-Boot] A command to discard saved environments?

[Masahiro Yamada]

Hi Fabio,


2016-08-03 12:34 GMT+09:00 Fabio Estevam <festevam@gmail.com>:
> On Wed, Aug 3, 2016 at 12:31 AM, Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
>> Hi.
>>
>>
>> I am looking for a command
>> that discards the saved environments,
>
> Does this command help?
>
> => env default -f -a
>


I know this command, but it is the manupulation
of working RAM in U-Boot.

If I reset my board,
it will load the saved environment again.



I want the environment data in a non-volatile device to go away.




-- 
Best Regards
Masahiro Yamada

[U-Boot] A command to discard saved environments?

[Tom Rini]

On Wed, Aug 03, 2016 at 12:49:09PM +0900, Masahiro Yamada wrote:
> Hi Fabio,
> 
> 
> 2016-08-03 12:34 GMT+09:00 Fabio Estevam <festevam@gmail.com>:
> > On Wed, Aug 3, 2016 at 12:31 AM, Masahiro Yamada
> > <yamada.masahiro@socionext.com> wrote:
> >> Hi.
> >>
> >>
> >> I am looking for a command
> >> that discards the saved environments,
> >
> > Does this command help?
> >
> > => env default -f -a
> >
> 
> 
> I know this command, but it is the manupulation
> of working RAM in U-Boot.
> 
> If I reset my board,
> it will load the saved environment again.
> 
> 
> 
> I want the environment data in a non-volatile device to go away.

I think I'm missing something.  As Fabio said env default -f -a will
reset it.  And then you can saveenv it.  If you want to restrict certain
parts of the environment check out the stuff around *ENV_FLAGS* and of
course if you just want to never have persistent environment, change to
ENV_IS_NOWHERE.  We don't have a way to tell U-Boot to ignore the valid
environment that it did find.

-- 
Tom
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[U-Boot] A command to discard saved environments?

[James Chargin]

I know my non-volatile copy of the environment is in NOR flash so I use 
the command

protect all off;erase <saved env address> +1

But, of course this is specific to NOR flash.

I'm not aware of a way to do this in the general case, independent of NV 
environment storage media and redundancy.

I'd be supportive of having a way to do this.

Jim

On 08/02/2016 08:31 PM, Masahiro Yamada wrote:
> Hi.
>
>
> I am looking for a command
> that discards the saved environments,
> and takes me back to the
> "*** Warning - bad CRC, using default environment" state.
>
>
> In my case, the environment data is saved
> at sector 0x400 of the MMC device on my board.
>
>
> So, I can just do
>
>  > mmc erase 400 10
>
>
> But, beforehand, I need to know
>
> CONFIG_ENV_IS_IN_MMC
> CONFIG_ENV_OFFSET     0x80000
>
> in order to confirm if the above command is doing the right thing.
> (If I make a mistake in calculating the offset value,
> other data would be damaged.)
>
>
>
> Is there a nice command to do that?
>
>
>

-- 
Jim Chargin
AJA Video Systems                       jimc at aja.com
(530) 271-3334                          http://www.aja.com

[U-Boot] A command to discard saved environments?

[Wolfgang Denk]

Dear James,

In message <fcff97bb-d146-fc77-28e4-050cac0922f4@gmail.com> you wrote:
> I know my non-volatile copy of the environment is in NOR flash so I use 
> the command
> 
> protect all off;erase <saved env address> +1
> 
> But, of course this is specific to NOR flash.
> 
> I'm not aware of a way to do this in the general case, independent of NV 
> environment storage media and redundancy.

The idea applies to all kinds of persistent storage: just overwrite a
few (4 or more) bytes at the beginning of each copy of the persistent
envrionment.

In your case, you could save the "erase" by overwriting the first 4
bytes (where the CRC32 checksum is stored) with 0xFFFFFFFF.

> I'd be supportive of having a way to do this.

No, I don't think we want to support this.  The persistent copy of the
environment is a precious resource, and I cannot think of a regular
use case to invalidate this.  If you do, the result is that you will
use the default settings at next boot - and the samve effect can be
acchieved by using "env reset" + "env save" as already recommended.
[The only difference is that you will not see the "invalid CRC, using
the default env" warning then, but I consider this a pro, not a con.]

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Test everything. Hold on to the good.          - 1 Thessalonians 5:21

[U-Boot] A command to discard saved environments?

[James Chargin]

Dear Wolfgang,

On 08/03/2016 12:59 PM, Wolfgang Denk wrote:
> Dear James,
>
> In message <fcff97bb-d146-fc77-28e4-050cac0922f4@gmail.com> you wrote:
>> I know my non-volatile copy of the environment is in NOR flash so I use
>> the command
>>
>> protect all off;erase <saved env address> +1
>>
>> But, of course this is specific to NOR flash.
>>
>> I'm not aware of a way to do this in the general case, independent of NV
>> environment storage media and redundancy.
>
> The idea applies to all kinds of persistent storage: just overwrite a
> few (4 or more) bytes at the beginning of each copy of the persistent
> envrionment.
>
> In your case, you could save the "erase" by overwriting the first 4
> bytes (where the CRC32 checksum is stored) with 0xFFFFFFFF.

In the case of my NOR flash storage, telling erase to do one byte 
actually causes the erasure of an entire flash sector, which we've 
reserved for the NV environment.  You are of course correct that 
overwriting the CRC will have the same operational effect.

In my shop, time is not critical, whereas simplicity of commands is 
valued by those I have to instruct to get this sort of operation done.

It's a rare occurrence that we need to do this, we don't use this sort 
of operation as a normal part of doing business.

>
>> I'd be supportive of having a way to do this.
>
> No, I don't think we want to support this.  The persistent copy of the
> environment is a precious resource, and I cannot think of a regular
> use case to invalidate this.  If you do, the result is that you will
> use the default settings at next boot - and the samve effect can be
> acchieved by using "env reset" + "env save" as already recommended.
> [The only difference is that you will not see the "invalid CRC, using
> the default env" warning then, but I consider this a pro, not a con.]

Thank you for this perspective. I often feel a bit isolated in my way of 
doing things and I find it valuable to read things like this.

I agree that there is not a regular use for an operation of this sort.

During development and debug, I will occasionally need to restore a 
particular system to the physical state it would be in had we just 
received it from our contract manufacturer, which would include a blank 
area in NOR flash where the U-Boot environment is kept. This is done 
usually to "prove" that processes will work on those systems from the CM 
when production starts.

Up to now, I've used the erase command to do this and I will continue to 
do things this way. I guess I've been at this long enough that the rare 
times I need to erase this area of flash has become noticeable as a pattern.

Again, thank you for your reply.

Regards,
Jim

>
> Best regards,
>
> Wolfgang Denk
>

-- 
Jim Chargin
AJA Video Systems                       jimc at aja.com
(530) 271-3334                          http://www.aja.com

[U-Boot] A command to discard saved environments?

[Wolfgang Denk]

Dear James,

In message <d18f75c7-388b-b607-ed70-64a250320d5a@gmail.com> you wrote:
> 
> > In your case, you could save the "erase" by overwriting the first 4
> > bytes (where the CRC32 checksum is stored) with 0xFFFFFFFF.

Wrong.  I meant writing 0x00000000 - as you can always write that,
setting any remaining 1 bits to 0 which does not require an erase of
the sector.

> In the case of my NOR flash storage, telling erase to do one byte 
> actually causes the erasure of an entire flash sector, which we've 
> reserved for the NV environment.  You are of course correct that 
> overwriting the CRC will have the same operational effect.

...and as the next "saveenv" will start with an erase, writing 0 to
the CRC 32 field saves you one erase cycle on that sector.

I know, this is nitpicking. Soryy.

> It's a rare occurrence that we need to do this, we don't use this sort 
> of operation as a normal part of doing business.

Agreed. This should never be part of regular operation.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Microsoft Multitasking:
                     several applications can crash at the same time.

[U-Boot] A command to discard saved environments?

[Masahiro Yamada]

2016-08-04 14:40 GMT+09:00 Wolfgang Denk <wd@denx.de>:
> Dear James,
>
> In message <d18f75c7-388b-b607-ed70-64a250320d5a@gmail.com> you wrote:
>>
>> > In your case, you could save the "erase" by overwriting the first 4
>> > bytes (where the CRC32 checksum is stored) with 0xFFFFFFFF.
>
> Wrong.  I meant writing 0x00000000 - as you can always write that,
> setting any remaining 1 bits to 0 which does not require an erase of
> the sector.
>
>> In the case of my NOR flash storage, telling erase to do one byte
>> actually causes the erasure of an entire flash sector, which we've
>> reserved for the NV environment.  You are of course correct that
>> overwriting the CRC will have the same operational effect.
>
> ...and as the next "saveenv" will start with an erase, writing 0 to
> the CRC 32 field saves you one erase cycle on that sector.
>
> I know, this is nitpicking. Soryy.
>
>> It's a rare occurrence that we need to do this, we don't use this sort
>> of operation as a normal part of doing business.
>
> Agreed. This should never be part of regular operation.
>
> Best regards,
>
> Wolfgang Denk
>


Sorry for my late reply.


I was in the conflict between my coworkers from different schools.

One always wants to save his preference in the environments in a
non-volatile device.

Another wants to load "uEnv.txt" to adjust environments, so the
environments from a non-volatile device
are just annoying for him.  He just want to clean the saved
environments away, and makes the
sectors for environments to the initial state.


I was searching a way to make everyone happy.
As Tom pointed out, the latter can use CONFIG_ENV_IS_NOWHERE.
Thanks!

-- 
Best Regards
Masahiro Yamada

[U-Boot] A command to discard saved environments?

[Wolfgang Denk]

Dear Masahiro,

In message <CAK7LNATygXm=Z42SYYEXW9NJLYkFMa1gPQ8PB2_8Y4DUWYZOaQ@mail.gmail.com> you wrote:
>
> Another wants to load "uEnv.txt" to adjust environments, so the
> environments from a non-volatile device
> are just annoying for him.

This is largely a matter of taste, but I consider it as a perfectly
valid wish.

> He just want to clean the saved
> environments away, and makes the
> sectors for environments to the initial state.

This, on the other hand, is not reasonable.

If he does not like the saved environment, he is free to use the
regular "env" commands to define one he likes: "env default -f -a"
or "env default -f var ..." or "env delete -f var ..." followed by a
"env save" provide a lot of options.

There should be no need for manipulating stored data structures in
obscure ways.

One could discuss if an expension as "env delete -f -a" makes sense...

> As Tom pointed out, the latter can use CONFIG_ENV_IS_NOWHERE.

Of course. TIMTOWTDI...

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Harrisberger's Fourth Law of the Lab:
	Experience is directly proportional to the
	amount of equipment ruined.