[U-Boot] calling pci_init before relocation?

[U-Boot] calling pci_init before relocation?

[Michael Schwingen]

Hi,

ist it allowed to call pci_init before relocation?

The code looks like this is not supposed to happen. However, on ARM,
arm_pci_init (which calls pci_init in turn) is called from
init_sequence, which happens before relocation.

Am I overlooking some way in which this can actually work? Are there
boards using this?

If I move pci_init down into board_init_r, I can get PCI working on
IXP42x, but I am worried if this will cause problems on other boards.

cu
Michael

[U-Boot] calling pci_init before relocation?

[Albert ARIBAUD]

Hi Michael,

Le 30/01/2011 22:39, Michael Schwingen a ?crit :
> Hi,
>
> ist it allowed to call pci_init before relocation?
>
> The code looks like this is not supposed to happen. However, on ARM,
> arm_pci_init (which calls pci_init in turn) is called from
> init_sequence, which happens before relocation.
>
> Am I overlooking some way in which this can actually work? Are there
> boards using this?
>
> If I move pci_init down into board_init_r, I can get PCI working on
> IXP42x, but I am worried if this will cause problems on other boards.

I cannot see a reason why pci_init should not work before relocation as 
long as it does not read or write BSS variables or write non-const 
initialized data -- or overflow the (admittedly limited) C stack.

Are you asking because you discovered that pci_init does not work when 
called from board_init_f? If so, did you determine exactly what goes wrong?

> cu
> Michael

Amicalement,
-- 
Albert.

[U-Boot] calling pci_init before relocation?

[Michael Schwingen]

Am 01/30/2011 11:07 PM, schrieb Albert ARIBAUD:
> Hi Michael,
>
> Le 30/01/2011 22:39, Michael Schwingen a ?crit :
>> Hi,
>>
>> ist it allowed to call pci_init before relocation?
>>
>> The code looks like this is not supposed to happen. However, on ARM,
>> arm_pci_init (which calls pci_init in turn) is called from
>> init_sequence, which happens before relocation.
>>
>> Am I overlooking some way in which this can actually work? Are there
>> boards using this?
>>
>> If I move pci_init down into board_init_r, I can get PCI working on
>> IXP42x, but I am worried if this will cause problems on other boards.
> I cannot see a reason why pci_init should not work before relocation as 
> long as it does not read or write BSS variables or write non-const 
> initialized data -- or overflow the (admittedly limited) C stack.
Because it does just that - from drivers/pci/pci.c:

static struct pci_controller* hose_head;

void pci_init(void)
{
[...]
    hose_head = NULL;

    /* now call board specific pci_init()... */
    pci_init_board();
}

pci_init_board will then call code that ends up calling
pci_register_hose, which adds elements into the list at hose_head.

> Are you asking because you discovered that pci_init does not work when 
> called from board_init_f? If so, did you determine exactly what goes wrong?
The system hangs during early init, and does not get past relocation.

Note that I can only *test* PCI on IXP42x, however, this is common code,
so I do not see how this could behave different on other ARM systems.

If I interpret the code correct, the PCI code is called from
board_init_r on PowerPC platforms.

cu
Michael

[U-Boot] calling pci_init before relocation?

[Albert ARIBAUD]

Le 30/01/2011 23:46, Michael Schwingen a ?crit :
> Am 01/30/2011 11:07 PM, schrieb Albert ARIBAUD:
>> Hi Michael,
>>
>> Le 30/01/2011 22:39, Michael Schwingen a ?crit :
>>> Hi,
>>>
>>> ist it allowed to call pci_init before relocation?
>>>
>>> The code looks like this is not supposed to happen. However, on ARM,
>>> arm_pci_init (which calls pci_init in turn) is called from
>>> init_sequence, which happens before relocation.
>>>
>>> Am I overlooking some way in which this can actually work? Are there
>>> boards using this?
>>>
>>> If I move pci_init down into board_init_r, I can get PCI working on
>>> IXP42x, but I am worried if this will cause problems on other boards.
>> I cannot see a reason why pci_init should not work before relocation as
>> long as it does not read or write BSS variables or write non-const
>> initialized data -- or overflow the (admittedly limited) C stack.
> Because it does just that - from drivers/pci/pci.c:
>
> static struct pci_controller* hose_head;
>
> void pci_init(void)
> {
> [...]
>      hose_head = NULL;
>
>      /* now call board specific pci_init()... */
>      pci_init_board();
> }
>
> pci_init_board will then call code that ends up calling
> pci_register_hose, which adds elements into the list at hose_head.

Tough luck -- BTW, how does this code allocate the memory? The heap is 
obviously not going to work before relocation.

>> Are you asking because you discovered that pci_init does not work when
>> called from board_init_f? If so, did you determine exactly what goes wrong?
> The system hangs during early init, and does not get past relocation.
>
> Note that I can only *test* PCI on IXP42x, however, this is common code,
> so I do not see how this could behave different on other ARM systems.
>
> If I interpret the code correct, the PCI code is called from
> board_init_r on PowerPC platforms.

Hmm... Now let's reverse the question: why should PCI be initialized 
before relocation? At this point the only goal of the init_board_f code 
is to get the RAM working for relocation, and the only useful device is 
the serial console. Does pci_init() help for either RAM or console?

> cu
> Michael

Amicalement,
-- 
Albert.

[U-Boot] calling pci_init before relocation?

[Heiko Schocher]

Hello Albert, Michael,

Albert ARIBAUD wrote:
> Le 30/01/2011 23:46, Michael Schwingen a ?crit :
>> Am 01/30/2011 11:07 PM, schrieb Albert ARIBAUD:
>>> Hi Michael,
>>>
>>> Le 30/01/2011 22:39, Michael Schwingen a ?crit :
>>>> Hi,
>>>>
>>>> ist it allowed to call pci_init before relocation?
>>>>
>>>> The code looks like this is not supposed to happen. However, on ARM,
>>>> arm_pci_init (which calls pci_init in turn) is called from
>>>> init_sequence, which happens before relocation.
>>>>
>>>> Am I overlooking some way in which this can actually work? Are there
>>>> boards using this?
>>>>
>>>> If I move pci_init down into board_init_r, I can get PCI working on
>>>> IXP42x, but I am worried if this will cause problems on other boards.
>>> I cannot see a reason why pci_init should not work before relocation as
>>> long as it does not read or write BSS variables or write non-const
>>> initialized data -- or overflow the (admittedly limited) C stack.
>> Because it does just that - from drivers/pci/pci.c:
>>
>> static struct pci_controller* hose_head;
>>
>> void pci_init(void)
>> {
>> [...]
>>      hose_head = NULL;
>>
>>      /* now call board specific pci_init()... */
>>      pci_init_board();
>> }
>>
>> pci_init_board will then call code that ends up calling
>> pci_register_hose, which adds elements into the list at hose_head.
> 
> Tough luck -- BTW, how does this code allocate the memory? The heap is 
> obviously not going to work before relocation.
> 
>>> Are you asking because you discovered that pci_init does not work when
>>> called from board_init_f? If so, did you determine exactly what goes wrong?
>> The system hangs during early init, and does not get past relocation.
>>
>> Note that I can only *test* PCI on IXP42x, however, this is common code,
>> so I do not see how this could behave different on other ARM systems.
>>
>> If I interpret the code correct, the PCI code is called from
>> board_init_r on PowerPC platforms.
> 
> Hmm... Now let's reverse the question: why should PCI be initialized 
> before relocation? At this point the only goal of the init_board_f code 
> is to get the RAM working for relocation, and the only useful device is 
> the serial console. Does pci_init() help for either RAM or console?

I think, on arm plattforms we should move the pci_init as it is
done on powerpc plattforms, to board_init_r. It seems to me, that
this is a leftover from introducing relocation to arm. I also just
could think of using a "PCI console" before relocation... and if
I looked right, this is not used on any arm plattform ...

bye,
Heiko
-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

[U-Boot] calling pci_init before relocation?

[Michael Schwingen]

Albert ARIBAUD wrote:
> Le 30/01/2011 23:46, Michael Schwingen a ?crit :
>> Am 01/30/2011 11:07 PM, schrieb Albert ARIBAUD:
>>> Hi Michael,
>>>
>>> Le 30/01/2011 22:39, Michael Schwingen a ?crit :
>>>> Hi,
>>>>
>>>> ist it allowed to call pci_init before relocation?
>>>>
>>>> The code looks like this is not supposed to happen. However, on ARM,
>>>> arm_pci_init (which calls pci_init in turn) is called from
>>>> init_sequence, which happens before relocation.
>>>>
>>>> Am I overlooking some way in which this can actually work? Are there
>>>> boards using this?
>>>>
>>>> If I move pci_init down into board_init_r, I can get PCI working on
>>>> IXP42x, but I am worried if this will cause problems on other boards.
>>> I cannot see a reason why pci_init should not work before relocation as
>>> long as it does not read or write BSS variables or write non-const
>>> initialized data -- or overflow the (admittedly limited) C stack.
>> Because it does just that - from drivers/pci/pci.c:
>>
>> static struct pci_controller* hose_head;
>>
>> void pci_init(void)
>> {
>> [...]
>>      hose_head = NULL;
>>
>>      /* now call board specific pci_init()... */
>>      pci_init_board();
>> }
>>
>> pci_init_board will then call code that ends up calling
>> pci_register_hose, which adds elements into the list at hose_head.
>
> Tough luck -- BTW, how does this code allocate the memory? The heap is 
> obviously not going to work before relocation.
The new hose pointer is passed into that function - the calling code 
would have to either malloc that, or use a static struct (as it is done 
on IXP, because there is only one PCI bus). Both will fail before 
relocation - the hose structure would have to be embedded into the 
global data struct.

>
>>> Are you asking because you discovered that pci_init does not work when
>>> called from board_init_f? If so, did you determine exactly what goes 
>>> wrong?
>> The system hangs during early init, and does not get past relocation.
>>
>> Note that I can only *test* PCI on IXP42x, however, this is common code,
>> so I do not see how this could behave different on other ARM systems.
>>
>> If I interpret the code correct, the PCI code is called from
>> board_init_r on PowerPC platforms.
>
> Hmm... Now let's reverse the question: why should PCI be initialized 
> before relocation? At this point the only goal of the init_board_f 
> code is to get the RAM working for relocation, and the only useful 
> device is the serial console. Does pci_init() help for either RAM or 
> console?
I don't see a reason to do that - my vote would be to do the PCI 
initialization after relocation, but I am not sure if there are any ARM 
boards that need this for whatever reason. If there are any, I would 
expect them to be broken anyway since relocation was added, but I can't 
be sure.

cu
Michael

[U-Boot] calling pci_init before relocation?

[Wolfgang Denk]

Dear Michael Schwingen,

In message <4D45EA43.3070108@discworld.dascon.de> you wrote:
>
> The system hangs during early init, and does not get past relocation.

That is to be expected when you use this before relocation. Don't do
that, then.

> If I interpret the code correct, the PCI code is called from
> board_init_r on PowerPC platforms.

So what? board_init_r() is (quoting the comment) "the  next  part  if
the  initialization  sequence: we are now running from RAM and have a
"normal" C environment, i. e. global data can  be  written,  BSS  has
been cleared, the stack size in not that critical any more, etc."

So it's perfectly safe and clean to run pci_init() there.

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 whole problem with the world is  that  fools  and  fanatics  are
always so certain of themselves, but wiser people so full of doubts."
- Bertrand Russell

[U-Boot] calling pci_init before relocation?

[Wolfgang Denk]

Dear Heiko Schocher,

In message <4D4676A2.7060600@denx.de> you wrote:
> 
> I think, on arm plattforms we should move the pci_init as it is
> done on powerpc plattforms, to board_init_r. It seems to me, that

Indeed.

> this is a leftover from introducing relocation to arm. I also just
> could think of using a "PCI console" before relocation... and if
> I looked right, this is not used on any arm plattform ...

And even if it was used - it would have to be handled the same way
like console over Ethernet or USB: the console device becomes
available only after relocation in such configurations.

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 software required `Windows 95 or better', so I installed Linux.

[U-Boot] calling pci_init before relocation?

[Michael Schwingen]

Wolfgang Denk wrote:
> Dear Michael Schwingen,
>
> In message <4D45EA43.3070108@discworld.dascon.de> you wrote:
>   
>> The system hangs during early init, and does not get past relocation.
>>     
>
> That is to be expected when you use this before relocation. Don't do
> that, then.
>
>   
>> If I interpret the code correct, the PCI code is called from
>> board_init_r on PowerPC platforms.
>>     
>
> So what? board_init_r() is (quoting the comment) "the  next  part  if
> the  initialization  sequence: we are now running from RAM and have a
> "normal" C environment, i. e. global data can  be  written,  BSS  has
> been cleared, the stack size in not that critical any more, etc."
>
> So it's perfectly safe and clean to run pci_init() there.
>   
I know - I only wanted to point at the differences: the problem is that 
the ARM code does it before relocation currently, and I was trying to 
understand why.

cu
Michael

[U-Boot] calling pci_init before relocation?

[Michael Schwingen]

On 01/31/2011 09:45 AM, Heiko Schocher wrote:
>
> I think, on arm plattforms we should move the pci_init as it is
> done on powerpc plattforms, to board_init_r. It seems to me, that
> this is a leftover from introducing relocation to arm. I also just
> could think of using a "PCI console" before relocation... and if
> I looked right, this is not used on any arm plattform ...
Fine. I'll include that change with the other changes needed to get PCI 
up again on IXP425.

cu
Michael

[U-Boot] calling pci_init before relocation?

[Heiko Schocher]

Hello Michael,

Michael Schwingen wrote:
> On 01/31/2011 09:45 AM, Heiko Schocher wrote:
>>
>> I think, on arm plattforms we should move the pci_init as it is
>> done on powerpc plattforms, to board_init_r. It seems to me, that
>> this is a leftover from introducing relocation to arm. I also just
>> could think of using a "PCI console" before relocation... and if
>> I looked right, this is not used on any arm plattform ...
> Fine. I'll include that change with the other changes needed to get PCI
> up again on IXP425.

Ok, thanks!

bye,
Heiko
-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany