[U-Boot] U-boot SPL direct Linux boot

[U-Boot] U-boot SPL direct Linux boot

[Simon Schwarz]

Hi List,

for my bachelor thesis I will implement a direct Linux boot from U-Boot SPL.
My current plan is to utilize do_bootm_[OS].

Simplest solution is to direct boot Linux/other OS and just boot
u-boot when a key is pressed. In addition i will also have some tests
(header check/CRC) - if they fail start u-boot.

IMHO this may also be of interest for the new SPL architecture.

Are there already implementations I am not aware of? Any comments on
what I should also add? Problems I may not see?

Regards
Simon

[U-Boot] U-boot SPL direct Linux boot

[Heiko Schocher]

Hello Simon,

Simon Schwarz wrote:
> for my bachelor thesis I will implement a direct Linux boot from U-Boot SPL.
> My current plan is to utilize do_bootm_[OS].
> 
> Simplest solution is to direct boot Linux/other OS and just boot
> u-boot when a key is pressed. In addition i will also have some tests
> (header check/CRC) - if they fail start u-boot.
> 
> IMHO this may also be of interest for the new SPL architecture.
> 
> Are there already implementations I am not aware of? Any comments on
> what I should also add? Problems I may not see?

I tried this on an davinci dm368 based board (not in mainline yet,
but patches for the board support coming soon), with the following
patch:

[U-Boot] U-boot SPL direct Linux boot

[Simon Schwarz]

thanks Heiko! That seems like half of the work :)

> - we should define a struct, which contains the 3 values
>  offset, size, destination, so we can create a "nand_load_list"
>  which can contain n entries, that could be processed in
>  a while loop ... so no need for the CONFIG_SYS_BOOT_LINUX
>  define ;-)

I would also add some kind of CRC to check the integrity of the image?

Another question is if we not just use the uImage format provided by
mkImage. This IMHO should include all this (except the offset) but
then we have to read the first NAND-page (or what ever medium) to get
these values which presumably means a significant slow-down. But then
we can update the image without updating u-boot what i would consider
important for non-dev devices.

Regards
Simon

[U-Boot] U-boot SPL direct Linux boot

[Simon Schwarz]

Ok, topic ATAGS:
I see three ways doing ATAGS init for SPL:
1. use bootm.c which means init bd correctly and add a bunch of #ifdef
CONFIG_PRELOADER to it - maybe also to some others i don't have on the
radar yet.
2. Have ATAGS config in board config file and init it at compile time
3. Doing it like Heiko and copy the ATAGS config done by u-boot

My favourite here is number 2 because it would be faster than  1 and
won't take so much work and won't clutter the standard u-boot code
with #ifdefs. Also it is simpler to use than 3. the downside is that
the section for ATAGS config would be huge and the code could diverge
over time...

Comments?

Regards
Simon

[U-Boot] U-boot SPL direct Linux boot

[Detlev Zundel]

Hi Simon,

> Ok, topic ATAGS:
> I see three ways doing ATAGS init for SPL:
> 1. use bootm.c which means init bd correctly and add a bunch of #ifdef
> CONFIG_PRELOADER to it - maybe also to some others i don't have on the
> radar yet.
> 2. Have ATAGS config in board config file and init it at compile time
> 3. Doing it like Heiko and copy the ATAGS config done by u-boot
>
> My favourite here is number 2 because it would be faster than  1 and
> won't take so much work and won't clutter the standard u-boot code
> with #ifdefs. Also it is simpler to use than 3. the downside is that
> the section for ATAGS config would be huge and the code could diverge
> over time...
>
> Comments?

Just a probably dumb side question, but will ATAGS be deprecated once we
have the flat device tree also on ARM?  As I understand, fdt is certainly
the way to go forward, so maybe we can already start with that?  In that
case, the fdt blob will be another binary blob to be passed to the
kernel and as such should be independant of U-Boot.  So ideally in
U-Boot we have a pointer to the fdt but the fdt itself can be updated
independantly.

Just a thought.
  Detlev

-- 
When you  loosen yourself from  all the obvious delusions  - religion,
ideology,  Communism - you're  still left  with the  myth of  your own
goodness. Which is the final delusion.
                                          -- Philip Roth
--
DENX Software Engineering GmbH,      MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich,  Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-40 Fax: (+49)-8142-66989-80 Email: dzu at denx.de

[U-Boot] U-boot SPL direct Linux boot

[Simon Schwarz]

Hi Detlev,

> Just a probably dumb side question, but will ATAGS be deprecated once we
> have the flat device tree also on ARM? ?As I understand, fdt is certainly
> the way to go forward, so maybe we can already start with that? ?In that
> case, the fdt blob will be another binary blob to be passed to the
> kernel and as such should be independant of U-Boot. ?So ideally in
> U-Boot we have a pointer to the fdt but the fdt itself can be updated
> independantly.

I also thought about that. But I actually thought that FDT support for
ARM isn't ready yet - although I saw much code for it while I worked
on ATAGS. How is the FDT-state for ARM?
If it is already usable I would be happy to adapt it. But if not I
would prefer to stay with ATAGS (as I have a tight schedule for my BA
thesis).

Thx for your comment!

Regards
Simon

[U-Boot] U-boot SPL direct Linux boot

[Wolfgang Denk]

Dear Detlev,

In message <m21uyann8m.fsf@ohwell.denx.de> you wrote:
> 
> Just a probably dumb side question, but will ATAGS be deprecated once we
> have the flat device tree also on ARM?  As I understand, fdt is certainly

This is our understanding. For DT aware boards, no ATAGS are needed
/used any more.

> the way to go forward, so maybe we can already start with that?  In that
> case, the fdt blob will be another binary blob to be passed to the
> kernel and as such should be independant of U-Boot.  So ideally in
> U-Boot we have a pointer to the fdt but the fdt itself can be updated
> independantly.

Right.  That was the idea behind Heikos code: we don't actually care
what the kernel expects, we just pass it a binary blob and assume it
will understand it.  This may be a blob with ATAGs, or a blob with a
DT - only the kernel needs to know, the code in the SPL remains lean
and flexible.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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
It is dangerous to be right on a subject  on  which  the  established
authorities are wrong.                                    -- Voltaire

[U-Boot] U-boot SPL direct Linux boot

[Simon Schwarz]

Addition: As I read a bit about FDT it does not replace ATAGS
(http://elinux.org/Device_Trees) - it is more a supplement to it. So
it would not harm to implement minimal ATAGS support and later add the
FDT to it.

I started a prototype for ATAGS creation by modifying bootm.c - which
seems (so long) not be too hard. If this works and doesn't add too
much overhead FDT support is not that much a problem IMHO.

Regards
Simon

(Sorry Detlev for the repost - forgot the ML...)

[U-Boot] U-boot SPL direct Linux boot

[Igor Grinberg]

On 07/01/11 12:17, Simon Schwarz wrote:
> Ok, topic ATAGS:
> I see three ways doing ATAGS init for SPL:
> 1. use bootm.c which means init bd correctly and add a bunch of #ifdef
> CONFIG_PRELOADER to it - maybe also to some others i don't have on the
> radar yet.

While this is not clean, it might work good.

> 2. Have ATAGS config in board config file and init it at compile time

This is a problematic approach, because memory size, board revision,
serial number and may be some others are only known in runtime.

> 3. Doing it like Heiko and copy the ATAGS config done by u-boot

This one is probably the most clean way.

> My favourite here is number 2 because it would be faster than  1 and
> won't take so much work and won't clutter the standard u-boot code
> with #ifdefs. Also it is simpler to use than 3. the downside is that
> the section for ATAGS config would be huge and the code could diverge
> over time...

Regarding the device tree on ARM, it is still not fully functional.
Nevertheless, currently there is an attempt ([1] and [2]) to make kernel
work with both, device tree and ATAGS and if I understood correctly,
the ATAGS will have precedence over the DT, so closed source
boot loaders will still work.

[1] - http://www.spinics.net/lists/arm-kernel/msg128172.html
[2] - http://www.spinics.net/lists/arm-kernel/msg129270.html

-- 
Regards,
Igor.

[U-Boot] U-boot SPL direct Linux boot

[Simon Schwarz]

Thanks for your feedback Igor!

2011/7/1 Igor Grinberg <grinberg@compulab.co.il>:
> On 07/01/11 12:17, Simon Schwarz wrote:
>> Ok, topic ATAGS:
>> I see three ways doing ATAGS init for SPL:
>> 1. use bootm.c which means init bd correctly and add a bunch of #ifdef
>> CONFIG_PRELOADER to it - maybe also to some others i don't have on the
>> radar yet.
>
> While this is not clean, it might work good.
>
>> 2. Have ATAGS config in board config file and init it at compile time
>
> This is a problematic approach, because memory size, board revision,
> serial number and may be some others are only known in runtime.
>
>> 3. Doing it like Heiko and copy the ATAGS config done by u-boot
>
> This one is probably the most clean way.
>

The problem with approach 3 is that you need to copy the ATAGS image.
Is there a way to do this without a debugger? If yes it really could
be an alternative. If ATAGS and Kernel can be reflashed you can update
the kernel without a bootloader update (That's the main reason why i
switched to 1).

> Regarding the device tree on ARM, it is still not fully functional.
> Nevertheless, currently there is an attempt ([1] and [2]) to make kernel
> work with both, device tree and ATAGS and if I understood correctly,
> the ATAGS will have precedence over the DT, so closed source
> boot loaders will still work.
>
> [1] - http://www.spinics.net/lists/arm-kernel/msg128172.html
> [2] - http://www.spinics.net/lists/arm-kernel/msg129270.html

So, IMHO an ATAGS implementation for now is the better choice - a DT
patch then is, depending on the approach, not a big problem.

Regards
Simon

[U-Boot] U-boot SPL direct Linux boot

[Simon Schwarz]

Dear Wolfgang Denk,

a comment from your side would be nice - in what approach do you see
the best chance for getting it into mainline?

Regards
Simon

2011/7/1 Simon Schwarz <simonschwarzcor@googlemail.com>:
> Thanks for your feedback Igor!
>
> 2011/7/1 Igor Grinberg <grinberg@compulab.co.il>:
>> On 07/01/11 12:17, Simon Schwarz wrote:
>>> Ok, topic ATAGS:
>>> I see three ways doing ATAGS init for SPL:
>>> 1. use bootm.c which means init bd correctly and add a bunch of #ifdef
>>> CONFIG_PRELOADER to it - maybe also to some others i don't have on the
>>> radar yet.
>>
>> While this is not clean, it might work good.
>>
>>> 2. Have ATAGS config in board config file and init it at compile time
>>
>> This is a problematic approach, because memory size, board revision,
>> serial number and may be some others are only known in runtime.
>>
>>> 3. Doing it like Heiko and copy the ATAGS config done by u-boot
>>
>> This one is probably the most clean way.
>>
>
> The problem with approach 3 is that you need to copy the ATAGS image.
> Is there a way to do this without a debugger? If yes it really could
> be an alternative. If ATAGS and Kernel can be reflashed you can update
> the kernel without a bootloader update (That's the main reason why i
> switched to 1).
>
>> Regarding the device tree on ARM, it is still not fully functional.
>> Nevertheless, currently there is an attempt ([1] and [2]) to make kernel
>> work with both, device tree and ATAGS and if I understood correctly,
>> the ATAGS will have precedence over the DT, so closed source
>> boot loaders will still work.
>>
>> [1] - http://www.spinics.net/lists/arm-kernel/msg128172.html
>> [2] - http://www.spinics.net/lists/arm-kernel/msg129270.html
>
> So, IMHO an ATAGS implementation for now is the better choice - a DT
> patch then is, depending on the approach, not a big problem.
>
> Regards
> Simon
>

[U-Boot] U-boot SPL direct Linux boot

[Wolfgang Denk]

Dear Simon Schwarz,

In message <BANLkTimwHUopgQ4FLw4=ZmxYqHS1kH4kTA@mail.gmail.com> you wrote:
> 
> I also thought about that. But I actually thought that FDT support for
> ARM isn't ready yet - although I saw much code for it while I worked
> on ATAGS. How is the FDT-state for ARM?
> If it is already usable I would be happy to adapt it. But if not I
> would prefer to stay with ATAGS (as I have a tight schedule for my BA
> thesis).

FDT support has been stable for some time on a (growing) number of
reference boards.  See Grant Likely's tree for reference.

Speaking just for us (DENX): we will probably not do any new ARM Linux
port without FDT support any more.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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
In my experience the best way to get something done  is to give it to
someone who is busy.               - Terry Pratchett, _Going_Postal_

[U-Boot] U-boot SPL direct Linux boot

[Wolfgang Denk]

Dear Simon Schwarz,

In message <BANLkTinCM+qWU_D50LJgf6Am=7GgoErh4g@mail.gmail.com> you wrote:
> 
> > - we should define a struct, which contains the 3 values
> >  offset, size, destination, so we can create a "nand_load_list"
> >  which can contain n entries, that could be processed in
> >  a while loop ... so no need for the CONFIG_SYS_BOOT_LINUX
> >  define ;-)
> 
> I would also add some kind of CRC to check the integrity of the image?

If you add this, then please make sure to make it optional.  Keep in
mind that there are systems where the SPL code has to be really small
(like 4 or even 2 KiB).

> Another question is if we not just use the uImage format provided by
> mkImage. This IMHO should include all this (except the offset) but
> then we have to read the first NAND-page (or what ever medium) to get
> these values which presumably means a significant slow-down. But then
> we can update the image without updating u-boot what i would consider
> important for non-dev devices.

Reading an uImage and just skipping the 64 byte image header is
definitely an option.

Please keep the design simple - adding bells and whistles can be done
later, if there is room and time for it.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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
The goal of science is to build better mousetraps. The goal of nature
is to build better mice.

[U-Boot] U-boot SPL direct Linux boot

[Wolfgang Denk]

Dear Simon Schwarz,

In message <BANLkTikVPozuHtS92uV_H2oCmBord2d96w@mail.gmail.com> you wrote:
> 
> The problem with approach 3 is that you need to copy the ATAGS image.
> Is there a way to do this without a debugger? If yes it really could

You will need the ATAGs image only in U-Boot, so it should be
sufficient to use nand_write in U-Boot to write it to the location
where you later want to load it from.

> be an alternative. If ATAGS and Kernel can be reflashed you can update
> the kernel without a bootloader update (That's the main reason why i
> switched to 1).

There is no need to update the boot loader in this context.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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
How many seconds are there in a year? If I tell you there are 3.155 x
10^7, you won't even try to remember it. On the other hand, who could
forget that, to within half a percent, pi seconds is a nanocentury.
                                                - Tom Duff, Bell Labs

[U-Boot] U-boot SPL direct Linux boot

[Wolfgang Denk]

Dear Simon Schwarz,

In message <BANLkTikJ62qw9pnaq3HfRX7T9XwZ7p7PGA@mail.gmail.com> you wrote:
> 
> a comment from your side would be nice - in what approach do you see
> the best chance for getting it into mainline?

I already commented (see
http://article.gmane.org/gmane.comp.boot-loaders.u-boot/102491). I'm
all for simple and efficient solutions - i. e. approach # 3, as used
by Heiko.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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
If today is the first day of the rest of your life, what the hell was
yesterday?

[U-Boot] U-boot SPL direct Linux boot

[Grant Likely]

On Fri, Jul 1, 2011 at 10:42 AM, Simon Schwarz
<simonschwarzcor@googlemail.com> wrote:
> Addition: As I read a bit about FDT it does not replace ATAGS
> (http://elinux.org/Device_Trees) - it is more a supplement to it. So
> it would not harm to implement minimal ATAGS support and later add the
> FDT to it.

That was true in an early prototype, but it is not actually true
anymore.  Passing a DT replaces ATAGs on arm now, and that code is in
mainline.

>
> I started a prototype for ATAGS creation by modifying bootm.c - which
> seems (so long) not be too hard. If this works and doesn't add too
> much overhead FDT support is not that much a problem IMHO.
>
> Regards
> Simon
>
> (Sorry Detlev for the repost - forgot the ML...)
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot
>



-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.

[U-Boot] U-boot SPL direct Linux boot

[Simon Schwarz]

Thanks for all the responses!

I decided that the approach from Heiko really is the best/simplest one.

Later I will release a first patch as RFC for how saving of the
boot-params could be done.

With the implementation in the SPL boot I will wait until Aneesh V
finished his work on OMAP4/SPL.

Regards
Simon