[U-Boot] Chain loading an u-boot from an u-boot

[U-Boot] Chain loading an u-boot from an u-boot

[Helmut Raiger]

Hi,

     to give you some background why we would want to do something 
(strange) like this:

- we have a hardware design bug
- we have a few hundred i.MX31 TT-01 devices in the field
- the i.MX31 rom boot loader is only capable of using 1bit HW-ECC 
(loading the first page (2k) from the NAND)
- the NAND chip specifies a requirement of 1bit ECC for the first 128kB 
(PEB) and 4bit ECC for the rest
- our current u-boot uses 1-bit HW-ECC, the kernel uses UBIFS and 1bit 
HW-ECC
- we face increasing bit errors in the field in the PEBs used by u-boot.

Using UBIFS in the kernel mitigates the requirements of 4bit ECC for the 
whole NAND because it moves
PEBs when bit errors show up. The real problem is the area where u-boot 
is located (currently approx. 450kB,
including UBIFS, USB ethernet support and more ..).

So the idea was:

- use a small u-boot (<128kB) in the first PEB of the NAND (written with 
1bit HW-ECC) that supports 4bit BCH
- let it load a second u-boot (<512kB) from the next 4 PEBs (written 
with 4bit BCH)
- jump to the second u-boot and load the kernel from an UBI volume using 
1bit HW-ECC again

I did all that and it seemed to work just fine, but jumping to the 
second u-boot almost always
crashes the system. In detail we do:

- romboot loads the SPL (2kb)
- SPL loads the first u-boot stage (which relocates and runs nicely)
- the first u-boot 'boots' the second u-boot by loading it from the NAND
- the second u-boot is loaded to the link address minus 2kB (for SPL)
- this is the same for the first and the second u-boot  (link address 
0x87e00000 - 0x800 = 0x87dff800)
- it jumps to 0x87e00000 omitting the SPL for the second u-boot
- the second u-boot should relocated itself again

The second u-boot is verified in RAM with crc32 and it is valid.

I've tested many configuration and found, that it only works if both 
u-boots are identical:

- different builds of the same code work (different build date, but same 
code)
- different configurations never work
- it does not matter if cashes are turned on or off
- I skipped the relocation of the second u-boot (actually not necessary) 
to no avail

I also tried u-boot standalone applications which always work (after 
fixing a bug in u-boot r8<->r9 for gd),
again independent of cashes.
Using different configuration I never get any serial output of the 
second u-boot (board info) or debugging stuff.
If I set a breakpoint in the second u-boot (after relocation) and 
continue from there it works until it tries
to get the SPI clock (mxc_get_clock() when accessing CCM_CCMR) for the 
PMIC access.
If I throw in a mxc_dump_clocks() earlier it hangs there.

I'm pretty much running out of ideas, so any pointers are appreciated.

Thx
Helmut


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[U-Boot] Chain loading an u-boot from an u-boot

[Andreas Bießmann]

Dear Helmut Raiger,

On 02/10/2014 12:11 PM, Helmut Raiger wrote:
> Hi,
> 
>     to give you some background why we would want to do something
> (strange) like this:
> 
> - we have a hardware design bug
> - we have a few hundred i.MX31 TT-01 devices in the field
> - the i.MX31 rom boot loader is only capable of using 1bit HW-ECC
> (loading the first page (2k) from the NAND)
> - the NAND chip specifies a requirement of 1bit ECC for the first 128kB
> (PEB) and 4bit ECC for the rest
> - our current u-boot uses 1-bit HW-ECC, the kernel uses UBIFS and 1bit
> HW-ECC

D'oh!

> - we face increasing bit errors in the field in the PEBs used by u-boot.
> 
> Using UBIFS in the kernel mitigates the requirements of 4bit ECC for the
> whole NAND because it moves
> PEBs when bit errors show up. The real problem is the area where u-boot
> is located (currently approx. 450kB,
> including UBIFS, USB ethernet support and more ..).

I wouldn't say it is a good solution to have 1 bit ecc on NAND that
requires 4 bit, even though there is another layer reacting on bit
errors. I guess your BBT will increase significant in a very short time.

> So the idea was:
> 
> - use a small u-boot (<128kB) in the first PEB of the NAND (written with
> 1bit HW-ECC) that supports 4bit BCH

How about using SPL here? I don't know the freescale universe but wonder
if SPL is fixed to 2k. Building SPL with SW BCH in less than 2k seems
not doable for me.

> - let it load a second u-boot (<512kB) from the next 4 PEBs (written
> with 4bit BCH)
> - jump to the second u-boot and load the kernel from an UBI volume using
> 1bit HW-ECC again
> 
> I did all that and it seemed to work just fine, but jumping to the
> second u-boot almost always
> crashes the system. In detail we do:
> 
> - romboot loads the SPL (2kb)
> - SPL loads the first u-boot stage (which relocates and runs nicely)
> - the first u-boot 'boots' the second u-boot by loading it from the NAND
> - the second u-boot is loaded to the link address minus 2kB (for SPL)
> - this is the same for the first and the second u-boot  (link address
> 0x87e00000 - 0x800 = 0x87dff800)

The offset is about 125MiB, current mainline code tells me, that the
tt-01 board has just 128 MiB. It is likely your second uboot overwrites
the code of your first one while copying. You should link your code to
run at a far away address, maybe 0x80000000 ;)

> - it jumps to 0x87e00000 omitting the SPL for the second u-boot
> - the second u-boot should relocated itself again
> 
> The second u-boot is verified in RAM with crc32 and it is valid.
> 
> I've tested many configuration and found, that it only works if both
> u-boots are identical:
> 
> - different builds of the same code work (different build date, but same
> code)
> - different configurations never work
> - it does not matter if cashes are turned on or off
> - I skipped the relocation of the second u-boot (actually not necessary)
> to no avail
> 
> I also tried u-boot standalone applications which always work (after
> fixing a bug in u-boot r8<->r9 for gd),
> again independent of cashes.
> Using different configuration I never get any serial output of the
> second u-boot (board info) or debugging stuff.
> If I set a breakpoint in the second u-boot (after relocation) and
> continue from there it works until it tries
> to get the SPI clock (mxc_get_clock() when accessing CCM_CCMR) for the
> PMIC access.
> If I throw in a mxc_dump_clocks() earlier it hangs there.

Well, it may be related to some freescale interna I do not know. However
It is likely that you really overwrite the first u-boot version with the
second one.

> 
> I'm pretty much running out of ideas, so any pointers are appreciated.

Hope it helps ...

Best regards

Andreas Bie?mann

[U-Boot] Chain loading an u-boot from an u-boot

[Helmut Raiger]

On 02/10/2014 01:14 PM, Andreas Bie?mann wrote:
> - we have a hardware design bug
> - we have a few hundred i.MX31 TT-01 devices in the field
> - the i.MX31 rom boot loader is only capable of using 1bit HW-ECC
> (loading the first page (2k) from the NAND)
> - the NAND chip specifies a requirement of 1bit ECC for the first 128kB
> (PEB) and 4bit ECC for the rest
> - our current u-boot uses 1-bit HW-ECC, the kernel uses UBIFS and 1bit
> HW-ECC
> D'oh!
just about what I thought ...
> - we face increasing bit errors in the field in the PEBs used by u-boot.
>
> Using UBIFS in the kernel mitigates the requirements of 4bit ECC for the
> whole NAND because it moves
> PEBs when bit errors show up. The real problem is the area where u-boot
> is located (currently approx. 450kB,
> including UBIFS, USB ethernet support and more ..).
> I wouldn't say it is a good solution to have 1 bit ecc on NAND that
> requires 4 bit, even though there is another layer reacting on bit
> errors. I guess your BBT will increase significant in a very short time.
Most operations are read (we use a separate YAFFS partition for time 
predictable writes),
so UBI will relocate read-only blocks anyway (due to read disturbances), 
I think the
effect wont be too dramatic, but don't make me proof that ;-)

>> So the idea was:
>>
>> - use a small u-boot (<128kB) in the first PEB of the NAND (written with
>> 1bit HW-ECC) that supports 4bit BCH
> How about using SPL here? I don't know the freescale universe but wonder
> if SPL is fixed to 2k. Building SPL with SW BCH in less than 2k seems
> not doable for me.
SPL on i.MX31 is limited to 2kB so we can't use BCH 4 here, just as you 
guessed.


>> - let it load a second u-boot (<512kB) from the next 4 PEBs (written
>> with 4bit BCH)
>> - jump to the second u-boot and load the kernel from an UBI volume using
>> 1bit HW-ECC again
>>
>> I did all that and it seemed to work just fine, but jumping to the
>> second u-boot almost always
>> crashes the system. In detail we do:
>>
>> - romboot loads the SPL (2kb)
>> - SPL loads the first u-boot stage (which relocates and runs nicely)
>> - the first u-boot 'boots' the second u-boot by loading it from the NAND
>> - the second u-boot is loaded to the link address minus 2kB (for SPL)
>> - this is the same for the first and the second u-boot  (link address
>> 0x87e00000 - 0x800 = 0x87dff800)
> The offset is about 125MiB, current mainline code tells me, that the
> tt-01 board has just 128 MiB. It is likely your second uboot overwrites
> the code of your first one while copying. You should link your code to
> run at a far away address, maybe 0x80000000 ;)
We have 256MiB (not yet contributed).
First u-boot is loaded to 0x87e00000, then relocates to 0x8f... something.
Second u-booot is loaded to 0x87e00000 again and relocates to 0x8f...,
the same locations for both, the second u-boot is verified in RAM before 
jumping to it.
If I set a breakpoint in the do_go_exec() I can step right into the
second u-boot.
> Well, it may be related to some freescale interna I do not know. However
> It is likely that you really overwrite the first u-boot version with the
>
You'd be right for 128MiB!
I'll try to crc32 the relocated area of the first u-boot, anyway.

The strange thing is that the serial output does not show up unless I
set breakpoints. This might be pointing to some clock setup problem?!

Thx for caring,
Helmut

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[U-Boot] Chain loading an u-boot from an u-boot

[Scott Wood]

On Mon, 2014-02-10 at 13:57 +0100, Helmut Raiger wrote:
> On 02/10/2014 01:14 PM, Andreas Bie?mann wrote:
> > - we have a hardware design bug
> > - we have a few hundred i.MX31 TT-01 devices in the field
> > - the i.MX31 rom boot loader is only capable of using 1bit HW-ECC
> > (loading the first page (2k) from the NAND)
> > - the NAND chip specifies a requirement of 1bit ECC for the first 128kB
> > (PEB) and 4bit ECC for the rest
> > - our current u-boot uses 1-bit HW-ECC, the kernel uses UBIFS and 1bit
> > HW-ECC
> > D'oh!
> just about what I thought ...
> > - we face increasing bit errors in the field in the PEBs used by u-boot.
> >
> > Using UBIFS in the kernel mitigates the requirements of 4bit ECC for the
> > whole NAND because it moves
> > PEBs when bit errors show up. The real problem is the area where u-boot
> > is located (currently approx. 450kB,
> > including UBIFS, USB ethernet support and more ..).
> > I wouldn't say it is a good solution to have 1 bit ecc on NAND that
> > requires 4 bit, even though there is another layer reacting on bit
> > errors. I guess your BBT will increase significant in a very short time.
> Most operations are read (we use a separate YAFFS partition for time 
> predictable writes),
> so UBI will relocate read-only blocks anyway (due to read disturbances), 
> I think the
> effect wont be too dramatic, but don't make me proof that ;-)

This sounds like a very bad idea.

> >> So the idea was:
> >>
> >> - use a small u-boot (<128kB) in the first PEB of the NAND (written with
> >> 1bit HW-ECC) that supports 4bit BCH
> > How about using SPL here? I don't know the freescale universe but wonder
> > if SPL is fixed to 2k. Building SPL with SW BCH in less than 2k seems
> > not doable for me.
> SPL on i.MX31 is limited to 2kB so we can't use BCH 4 here, just as you 
> guessed.

You could use TPL (three stage extension of SPL).  2K SPL loads 126K
TPL, which has BCH code and can load the real U-Boot.

See doc/README.TPL, and include/configs/p1_p2_rdb_pc.h for an example.

> >> - let it load a second u-boot (<512kB) from the next 4 PEBs (written
> >> with 4bit BCH)
> >> - jump to the second u-boot and load the kernel from an UBI volume using
> >> 1bit HW-ECC again
> >>
> >> I did all that and it seemed to work just fine, but jumping to the
> >> second u-boot almost always
> >> crashes the system. In detail we do:
> >>
> >> - romboot loads the SPL (2kb)
> >> - SPL loads the first u-boot stage (which relocates and runs nicely)
> >> - the first u-boot 'boots' the second u-boot by loading it from the NAND
> >> - the second u-boot is loaded to the link address minus 2kB (for SPL)
> >> - this is the same for the first and the second u-boot  (link address
> >> 0x87e00000 - 0x800 = 0x87dff800)
> > The offset is about 125MiB, current mainline code tells me, that the
> > tt-01 board has just 128 MiB. It is likely your second uboot overwrites
> > the code of your first one while copying. You should link your code to
> > run at a far away address, maybe 0x80000000 ;)
> We have 256MiB (not yet contributed).
> First u-boot is loaded to 0x87e00000, then relocates to 0x8f... something.
> Second u-booot is loaded to 0x87e00000 again and relocates to 0x8f...,
> the same locations for both, the second u-boot is verified in RAM before 
> jumping to it.
> If I set a breakpoint in the do_go_exec() I can step right into the
> second u-boot.

Make sure you're cleaning the cache for that second load, if required.

-Scott

[U-Boot] Chain loading an u-boot from an u-boot

[Helmut Raiger]

On 02/12/2014 10:59 PM, Scott Wood wrote:
>>
>> Most operations are read (we use a separate YAFFS partition for time
>> predictable writes),
>> so UBI will relocate read-only blocks anyway (due to read disturbances),
>> I think the
>> effect wont be too dramatic, but don't make me proof that ;-)
> This sounds like a very bad idea.
Agreed.

>> SPL on i.MX31 is limited to 2kB so we can't use BCH 4 here, just as you
>> guessed.
> You could use TPL (three stage extension of SPL).  2K SPL loads 126K
> TPL, which has BCH code and can load the real U-Boot.
>
> See doc/README.TPL, and include/configs/p1_p2_rdb_pc.h for an example.
Yes I read that, but it's not done for i.mx31 and I thought it might
be harder to do, than just a second u-boot. This might proof wrong.

>> jumping to it.
>> If I set a breakpoint in the do_go_exec() I can step right into the
>> second u-boot.
> Make sure you're cleaning the cache for that second load, if required.

Currently I turned off cashes in the first u-boot and hoped that would
do.

Helmut


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[U-Boot] Chain loading an u-boot from an u-boot

[Stefano Babic]

Hi Helmut,

On 10/02/2014 12:11, Helmut Raiger wrote:

> 
> So the idea was:
> 
> - use a small u-boot (<128kB) in the first PEB of the NAND (written with
> 1bit HW-ECC) that supports 4bit BCH
> - let it load a second u-boot (<512kB) from the next 4 PEBs (written
> with 4bit BCH)
> - jump to the second u-boot and load the kernel from an UBI volume using
> 1bit HW-ECC again

I understand the first two points, but why do you store the kernel again
with 1bit HW-ECC ? The second U-Boot is able to check with 4bit BCH and
your NAND requires 4bit.

> 
> I did all that and it seemed to work just fine, but jumping to the
> second u-boot almost always
> crashes the system. In detail we do:
> 
> - romboot loads the SPL (2kb)
> - SPL loads the first u-boot stage (which relocates and runs nicely)
> - the first u-boot 'boots' the second u-boot by loading it from the NAND
> - the second u-boot is loaded to the link address minus 2kB (for SPL)
> - this is the same for the first and the second u-boot  (link address
> 0x87e00000 - 0x800 = 0x87dff800)
> - it jumps to 0x87e00000 omitting the SPL for the second u-boot
> - the second u-boot should relocated itself again
> 
> The second u-boot is verified in RAM with crc32 and it is valid.
> 
> I've tested many configuration and found, that it only works if both
> u-boots are identical:
> 
> - different builds of the same code work (different build date, but same
> code)

I agree with Andreas' analyses. It seems that the second u-boot
overwrites your running U-Boot and only if they are identical you have
no problem, that means that you are not changing the running code.

Regards,
Stefano Babic

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HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-53 Fax: +49-8142-66989-80 Email: sbabic at denx.de
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[U-Boot] Chain loading an u-boot from an u-boot

[Helmut Raiger]

Hi Stefano,
> Hi Helmut,
>
>
> I understand the first two points, but why do you store the kernel again
> with 1bit HW-ECC ? The second U-Boot is able to check with 4bit BCH and
> your NAND requires 4bit.

This is mainly due to performance requirements. Using 4bit BCH
increases overhead and makes DMA (currently not used in the
kernel driver) a lot slower. We thought we might slip through with
1bit HW-ECC, but we will test this (hopefully not in the field this time 
;-) )
> I agree with Andreas' analyses. It seems that the second u-boot
> overwrites your running U-Boot and only if they are identical you have
> no problem, that means that you are not changing the running code.
I double-checked now, the running u-boot is not overwritten.
When the 2nd u-boot relocates it overwrites the first one, but
that shouldn't be a problem. The first u-boot keeps working after
loading (but not running) the second one without issues.

Only the 'go' crashes the system. u-boot starts stand-alone
application fine, just as the kernel. I really can't see the point
why another u-boot should be any different?!

Helmut


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[U-Boot] Chain loading an u-boot from an u-boot

[Stefano Babic]

Hi Helmut,

On 12/02/2014 10:56, Helmut Raiger wrote:
> This is mainly due to performance requirements. Using 4bit BCH
> increases overhead and makes DMA (currently not used in the
> kernel driver) a lot slower. We thought we might slip through with
> 1bit HW-ECC, but we will test this (hopefully not in the field this time
> ;-) )

I know the MX31's NAND controller can only handle 1bit HW ECC ;-(

Let's know us your results - in my experience, when the NAND controller
(I am not speaking about MX31, anyway) provides less ECC bits as
requested by NAND, I always got problems. Sometimes UBIFS recovered it,
but I got the point when rootfs was not mounted.

> I double-checked now, the running u-boot is not overwritten.
> When the 2nd u-boot relocates it overwrites the first one, but
> that shouldn't be a problem. The first u-boot keeps working after
> loading (but not running) the second one without issues.
> 
> Only the 'go' crashes the system. u-boot starts stand-alone
> application fine, just as the kernel. I really can't see the point
> why another u-boot should be any different?!
> 

ok - then it could be that something is set twice (from first and second
U-Boot), and it crashes the second time is set. Of course, the DDR
controller must not be set by second U-Boot, but I suppose you have
already commented out.

Maybe setting the main clock again (I see it in board_setup_clocks() )
can cause some problems. Is it called again in your modified U-Boot ?
I am expecting that board_setup_sdram() and  board_setup_clocks() are
called only by your SPL.

Best regards,
Stefano Babic

-- 
=====================================================================
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-53 Fax: +49-8142-66989-80 Email: sbabic at denx.de
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[U-Boot] Chain loading an u-boot from an u-boot

[Andreas Bießmann]

Hi Helmut,

On 02/12/2014 10:56 AM, Helmut Raiger wrote:
>> I understand the first two points, but why do you store the kernel again
>> with 1bit HW-ECC ? The second U-Boot is able to check with 4bit BCH and
>> your NAND requires 4bit.
> 
> This is mainly due to performance requirements. Using 4bit BCH
> increases overhead and makes DMA (currently not used in the
> kernel driver) a lot slower. We thought we might slip through with
> 1bit HW-ECC, but we will test this (hopefully not in the field this time
> ;-) )

If your HW requires 4Bit it is highly recommended to do so. You will run
your HW out of specs in other case and I think it is hard to qualify
that 4Bit required ECC runs with 1Bit ECC and UBIFS as you stated in a
previous mail.

>> I agree with Andreas' analyses. It seems that the second u-boot
>> overwrites your running U-Boot and only if they are identical you have
>> no problem, that means that you are not changing the running code.
> I double-checked now, the running u-boot is not overwritten.
> When the 2nd u-boot relocates it overwrites the first one, but
> that shouldn't be a problem. The first u-boot keeps working after
> loading (but not running) the second one without issues.
> 
> Only the 'go' crashes the system. u-boot starts stand-alone
> application fine, just as the kernel. I really can't see the point
> why another u-boot should be any different?!

Just thinking ... have you checked the global data pointer? Is it
possible that the global data of the first u-boot influences the global
data of the second one?

Best regards

Andreas Bie?mann

[U-Boot] Chain loading an u-boot from an u-boot

[Helmut Raiger]

On 02/12/2014 11:45 AM, Andreas Bie?mann wrote:
> Hi Helmut,
>
> On 02/12/2014 10:56 AM, Helmut Raiger wrote:
>>> I understand the first two points, but why do you store the kernel again
>>> with 1bit HW-ECC ? The second U-Boot is able to check with 4bit BCH and
>>> your NAND requires 4bit.
>> This is mainly due to performance requirements. Using 4bit BCH
>> increases overhead and makes DMA (currently not used in the
>> kernel driver) a lot slower. We thought we might slip through with
>> 1bit HW-ECC, but we will test this (hopefully not in the field this time
>> ;-) )
> If your HW requires 4Bit it is highly recommended to do so. You will run
> your HW out of specs in other case and I think it is hard to qualify
> that 4Bit required ECC runs with 1Bit ECC and UBIFS as you stated in a
> previous mail.
You guys are right. I'm just cornered, as performance is a big issue aswell.
We'll try to qualify the NAND in proper climate and some UBIFS supervision
to gain more insight. Its just that teh application software guys suggested
to improve the kernel driver to use DMA to increase overall performance.

>> why another u-boot should be any different?!
> Just thinking ... have you checked the global data pointer? Is it
> possible that the global data of the first u-boot influences the global
> data of the second one?

The global data pointer is setup right before the newly set stack pointer
in arch/arm/lib/crt0.S, so it should be reset anyway.

And answering Stefano's question. The RAM setup is only in
the SPL which is skipped when I jump to the second u-boot.

But you just inspired me! There are probably interrupts running
for some time when the second u-boot starts and the relocation
might destroy part of the interrupt entry points ....

Thx for asking the right questions.
I'll have to check this.

Helmut


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[U-Boot] Chain loading an u-boot from an u-boot

[Helmut Raiger]

On 02/13/2014 10:03 AM, Helmut Raiger wrote:
>
>
> But you just inspired me! There are probably interrupts running
> for some time when the second u-boot starts and the relocation
> might destroy part of the interrupt entry points ....
>
> Thx for asking the right questions.
> I'll have to check this.
>
> Helmut

I'm finally able to start the second u-boot (other things in-between as 
always).
If I do a cleanup_before_linux(), i.e. turn off interrupts and caches before
the actual 'go' and it works just fine.

For testing I patched the go command, but obviously this can't be
contributed as such.

Anyone having a suggestion on how to do this?

1) add option to 'go' command, which is hard as it has variable arguments
2) add another go command
3) use an environment variable to set the option for 'go'

Theoretically I could use a u-boot image to encapsulate the second u-boot
and use 'bootm', but I think I'll stumble over the same kind of questions.

Helmut


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[U-Boot] Chain loading an u-boot from an u-boot

[Simon Glass]

Hi Hemut,

On 31 March 2014 05:29, Helmut Raiger <helmut.raiger@hale.at> wrote:

> On 02/13/2014 10:03 AM, Helmut Raiger wrote:
>
>>
>>
>> But you just inspired me! There are probably interrupts running
>> for some time when the second u-boot starts and the relocation
>> might destroy part of the interrupt entry points ....
>>
>> Thx for asking the right questions.
>> I'll have to check this.
>>
>> Helmut
>>
>
> I'm finally able to start the second u-boot (other things in-between as
> always).
> If I do a cleanup_before_linux(), i.e. turn off interrupts and caches
> before
> the actual 'go' and it works just fine.
>
> For testing I patched the go command, but obviously this can't be
> contributed as such.
>
> Anyone having a suggestion on how to do this?
>
> 1) add option to 'go' command, which is hard as it has variable arguments
> 2) add another go command
> 3) use an environment variable to set the option for 'go'
>
> Theoretically I could use a u-boot image to encapsulate the second u-boot
> and use 'bootm', but I think I'll stumble over the same kind of questions.


There is already 'dcache off' but I wonder if something like 'go prepare'
would be useful? Another option is that bootm has a prepare state, but it
requires an image.

Regards,
Simon

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[U-Boot] Chain loading an u-boot from an u-boot

[Stefano Babic]

Hi Helmut,

On 04/04/2014 01:13, Simon Glass wrote:

>> 1) add option to 'go' command, which is hard as it has variable arguments
>> 2) add another go command
>> 3) use an environment variable to set the option for 'go'
>>
>> Theoretically I could use a u-boot image to encapsulate the second u-boot
>> and use 'bootm', but I think I'll stumble over the same kind of questions.
> 
> 
> There is already 'dcache off' but I wonder if something like 'go prepare'
> would be useful? Another option is that bootm has a prepare state, but it
> requires an image.

I agree with Simon. If you have not changed your target, you are using a
MX31 and what cleanup_linux for arm1136 does is turning off the caches.
What about if you turn off i-cache and d-cache in einem script before
the go command ?

Best regards,
Stefano

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[U-Boot] Chain loading an u-boot from an u-boot

[Helmut Raiger]

On 04/04/2014 11:25 AM, Stefano Babic wrote:
> Hi Helmut,
>
> On 04/04/2014 01:13, Simon Glass wrote:
>
>>> 1) add option to 'go' command, which is hard as it has variable arguments
>>> 2) add another go command
>>> 3) use an environment variable to set the option for 'go'
>>>
>>> Theoretically I could use a u-boot image to encapsulate the second u-boot
>>> and use 'bootm', but I think I'll stumble over the same kind of questions.
>>
>> There is already 'dcache off' but I wonder if something like 'go prepare'
>> would be useful? Another option is that bootm has a prepare state, but it
>> requires an image.
> I agree with Simon. If you have not changed your target, you are using a
> MX31 and what cleanup_linux for arm1136 does is turning off the caches.
> What about if you turn off i-cache and d-cache in einem script before
> the go command ?
>
> Best regards,
> Stefano
>
Hi Stefano,

cleanup_before_linux() also disables interrupts and flushes the cache(s).
Simply turning off the caches did not do the trick.

Using 'go prepare' would be a solution as the 2nd argument should be an 
address (i.e. numeric) in any case.

Thx,
Helmut


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