[U-Boot] T4QDS e6500 core and U-Boot 64-bit

[U-Boot] T4QDS e6500 core and U-Boot 64-bit

[Danny Gale]

Hi All,

The T4240 on the T4QDS board is a PPC e6500 core (64 bit), but it is 
configured in U-Boot as an e500 core, which is 32 bit. Why is this? Can 
it be updated to e6500?

This leads directly into another question: can U-Boot be compiled and 
run 64-bit? So far, I have been unable to make it work with a 64-bit 
compiler. I'm running into these errors:

cc1: error: -mcall not supported in this configuration
cc1: error: -mrelocatable not supported in this configuration
cc1: error: -meabi not supported in this configuration

Specifying CFLAGS="-meabi -mrelocatable -mcall-sysv" will get through 
make T4240QDS_config without errors, but the above errors show up when 
making the following targets:
 > include/autoconf.mk
 > include/autoconf.mk.dep
 > include/spl-autoconf.mk
 > include/tpl-autoconf.mk

The build then fails, with a call to cross-gcc which does not include 
the specified CFLAGS. Is this a bug in the Makefile, that CFLAGS is not 
being passed to the call to cross-gcc?

Thanks,
Danny

[U-Boot] T4QDS e6500 core and U-Boot 64-bit

[Wolfgang Denk]

Dear Danny Gale,

In message <52DF18B3.1080904@coloradoengineeringinc.com> you wrote:
> 
> The T4240 on the T4QDS board is a PPC e6500 core (64 bit), but it is 
> configured in U-Boot as an e500 core, which is 32 bit. Why is this?

Becuase it simply works :-)

> Can it be updated to e6500?

Yes - if you add support for 64 bit configurations in general, and
for powerpc64 in particular.

> This leads directly into another question: can U-Boot be compiled and 
> run 64-bit? So far, I have been unable to make it work with a 64-bit 
> compiler. I'm running into these errors:

Not out of the box.


What is your actual reason for wanting to run a 64 bit boot loader?

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
1st Old Man:  Gee, its windy today.
2nd Old Man:  No it's not... it's Thursday.
3rd Old Man:  Yeh, me too.  Let's go for a beer.

[U-Boot] T4QDS e6500 core and U-Boot 64-bit

[Danny Gale]

Hi Wolfgang,

Thanks for your reply. My responses are inline below.

On 1/22/2014 2:06 AM, Wolfgang Denk wrote:
> Dear Danny Gale,
>
> In message <52DF18B3.1080904@coloradoengineeringinc.com> you wrote:
>> The T4240 on the T4QDS board is a PPC e6500 core (64 bit), but it is
>> configured in U-Boot as an e500 core, which is 32 bit. Why is this?
> Becuase it simply works :-)
>
>> Can it be updated to e6500?
> Yes - if you add support for 64 bit configurations in general, and
> for powerpc64 in particular.
I don't even have a sense for what would be involved here. How 
fundamentally would the U-Boot code need to change?
>> This leads directly into another question: can U-Boot be compiled and
>> run 64-bit? So far, I have been unable to make it work with a 64-bit
>> compiler. I'm running into these errors:
> Not out of the box.
>
>
> What is your actual reason for wanting to run a 64 bit boot loader?
My reason for wanting to run 64-bit is that this system has 12 GB of 
RAM. Will 32-bit U-Boot be able to access and test more than 4 GB of RAM?

Thanks again,
Danny

[U-Boot] T4QDS e6500 core and U-Boot 64-bit

[Scott Wood]

On Thu, 2014-01-23 at 11:13 -0700, Danny Gale wrote:
> Hi Wolfgang,
> 
> Thanks for your reply. My responses are inline below.
> 
> On 1/22/2014 2:06 AM, Wolfgang Denk wrote:
> > Dear Danny Gale,
> >
> > In message <52DF18B3.1080904@coloradoengineeringinc.com> you wrote:
> >> The T4240 on the T4QDS board is a PPC e6500 core (64 bit), but it is
> >> configured in U-Boot as an e500 core, which is 32 bit. Why is this?
> > Becuase it simply works :-)
> >
> >> Can it be updated to e6500?
> > Yes - if you add support for 64 bit configurations in general, and
> > for powerpc64 in particular.
> I don't even have a sense for what would be involved here. How 
> fundamentally would the U-Boot code need to change?

The common U-Boot code should be more or less OK -- the armv8 target
runs as 64-bit, and sandbox can as well.  The PPC code is another
matter, though.  You'd need to hack up or replace a bunch of asm code at
the least.

> >> This leads directly into another question: can U-Boot be compiled and
> >> run 64-bit? So far, I have been unable to make it work with a 64-bit
> >> compiler. I'm running into these errors:
> > Not out of the box.
> >
> >
> > What is your actual reason for wanting to run a 64 bit boot loader?
> My reason for wanting to run 64-bit is that this system has 12 GB of 
> RAM. Will 32-bit U-Boot be able to access and test more than 4 GB of RAM?

32-bit U-Boot can detect (or otherwise know about) and tell the OS about
large amounts of RAM, but it can only directly access 2 GiB.

-Scott

[U-Boot] T4QDS e6500 core and U-Boot 64-bit

[Wolfgang Denk]

Dear Danny,

In message <52E15BAD.1020400@coloradoengineeringinc.com> you wrote:
> 
> > Yes - if you add support for 64 bit configurations in general, and
> > for powerpc64 in particular.
> I don't even have a sense for what would be involved here. How 
> fundamentally would the U-Boot code need to change?

It's probably heavy.  There is a ton of places where we assume we can
put an address in a "long" data type, etc.

> My reason for wanting to run 64-bit is that this system has 12 GB of 
> RAM. Will 32-bit U-Boot be able to access and test more than 4 GB of RAM?

No.  For the "access" part: usually this i not really needed.  U-Boot
is a boot loader, intended to load and start an OS.  for this, a 32
bit address space should be more than sufficient.  For the "test"
part, it is probably much easier to add a customized memory test (or
fix just the existing memory test such that it can be built for a 64
bit mode) and use this, then trying to run all of U-Boot in 64 bit
mode.

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
"No matter where you go, there you are..."          - Buckaroo Banzai

[U-Boot] T4QDS e6500 core and U-Boot 64-bit

[Scott Wood]

On Fri, 2014-01-24 at 14:45 +0100, Wolfgang Denk wrote:
> Dear Danny,
> 
> In message <52E15BAD.1020400@coloradoengineeringinc.com> you wrote:
> > 
> > > Yes - if you add support for 64 bit configurations in general, and
> > > for powerpc64 in particular.
> > I don't even have a sense for what would be involved here. How 
> > fundamentally would the U-Boot code need to change?
> 
> It's probably heavy.  There is a ton of places where we assume we can
> put an address in a "long" data type, etc.

That's not a problem on 64-bit.  It's putting a pointer in an "int" that
breaks.

-Scott

[U-Boot] T4QDS e6500 core and U-Boot 64-bit

[Timur Tabi]

On Fri, Jan 24, 2014 at 7:45 AM, Wolfgang Denk <wd@denx.de> wrote:
>
> For the "test"
> part, it is probably much easier to add a customized memory test (or
> fix just the existing memory test such that it can be built for a 64
> bit mode) and use this, then trying to run all of U-Boot in 64 bit
> mode.

There already is PowerPC memory test code in U-Boot that supports more
than 2GB.  It uses sliding TLB windows.  If it doesn't already support
12GB, then it should be easy to add that support.

[U-Boot] T4QDS e6500 core and U-Boot 64-bit

[York Sun]

On 01/25/2014 07:46 AM, Timur Tabi wrote:
> On Fri, Jan 24, 2014 at 7:45 AM, Wolfgang Denk <wd@denx.de> wrote:
>>
>> For the "test"
>> part, it is probably much easier to add a customized memory test (or
>> fix just the existing memory test such that it can be built for a 64
>> bit mode) and use this, then trying to run all of U-Boot in 64 bit
>> mode.
> 
> There already is PowerPC memory test code in U-Boot that supports more
> than 2GB.  It uses sliding TLB windows.  If it doesn't already support
> 12GB, then it should be easy to add that support.

If the target is to test memory, current u-boot supports 36-bit address to cover
64GB memory. As everybody explained, only 2GB is "visible" at a time. But
actually all memory are read to use (by Linux or other OS). The POST memory test
slides the 2GB window to cover all DDR. It will remap back the window, as you
would see the message on the console.

York