[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Kumar Gala]

Moving the interrupt vectors to low memory can cause issues if the code
gets overwritten via some image loading command (tftp, boot*, etc.) and
interrupts (like the decrementer are enabled).

On 85xx there is no reason to copy the interrupt vectors to low memory
since we can run them in high memory since we are a Book-E core.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
---

This is a fix for 1.3.4.

- k

 cpu/mpc85xx/start.S |   19 +++++--------------
 1 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/cpu/mpc85xx/start.S b/cpu/mpc85xx/start.S
index 10fe936..9c8b2a1 100644
--- a/cpu/mpc85xx/start.S
+++ b/cpu/mpc85xx/start.S
@@ -936,13 +936,6 @@ trap_init:
 	bgelr				/* return if r7>=r8 - just in case */

 	mflr	r4			/* save link register		*/
-1:
-	lwz	r0,0(r7)
-	stw	r0,0(r9)
-	addi	r7,r7,4
-	addi	r9,r9,4
-	cmplw	0,r7,r8
-	bne	1b

 	/*
 	 * relocate `hdlr' and `int_return' entries
@@ -973,9 +966,6 @@ trap_init:
 	cmplw	0,r7,r8
 	blt	2b

-	lis	r7,0x0
-	mtspr	IVPR,r7
-
 	mtlr	r4			/* restore link register	*/
 	blr

@@ -983,13 +973,14 @@ trap_init:
 	 * Function: relocate entries for one exception vector
 	 */
 trap_reloc:
-	lwz	r0,0(r7)		/* hdlr ...			*/
+	lwzx	r0,r3,r7		/* hdlr ...			*/
 	add	r0,r0,r3		/*  ... += dest_addr		*/
-	stw	r0,0(r7)
+	stwx	r0,r3,r7

-	lwz	r0,4(r7)		/* int_return ...		*/
+	addi	r7,r7,4
+	lwzx	r0,r3,r7		/* int_return ...		*/
 	add	r0,r0,r3		/*  ... += dest_addr		*/
-	stw	r0,4(r7)
+	stwx	r0,r3,r7

 	blr

-- 
1.5.5.1

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Wolfgang Denk]

In message <Pine.LNX.4.64.0808060127560.20220@blarg.am.freescale.net> you wrote:
> Moving the interrupt vectors to low memory can cause issues if the code
> gets overwritten via some image loading command (tftp, boot*, etc.) and
> interrupts (like the decrementer are enabled).

Oops? This is expected and normal behaviour. Did anybody complain
about this?

> On 85xx there is no reason to copy the interrupt vectors to low memory
> since we can run them in high memory since we are a Book-E core.

High memory means leave them in flash?

Then you will probably see nice crashes as soon as you erase U-Boot
for example to install a new version.

All references to flash memory must be relocated to RAM, including the
exception vectors, of course.

> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
> ---
> 
> This is a fix for 1.3.4.

I don't think so. Seems to introduce a bug.

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 follows that any commander in chief who undertakes to carry out a
plan which he considers defective is at fault; he must put forth  his
reasons,  insist  of  the  plan being changed, and finally tender his
resignation rather than be the instrument of his army's downfall."
- Napoleon, "Military Maxims and Thought"

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Kumar Gala]

On Aug 6, 2008, at 1:50 AM, Wolfgang Denk wrote:

> In message <Pine.LNX. 
> 4.64.0808060127560.20220 at blarg.am.freescale.net> you wrote:
>> Moving the interrupt vectors to low memory can cause issues if the  
>> code
>> gets overwritten via some image loading command (tftp, boot*, etc.)  
>> and
>> interrupts (like the decrementer are enabled).
>
> Oops? This is expected and normal behaviour. Did anybody complain
> about this?

Real, any reason why?  I understand on classic PPC this might be the  
case but I see no reason for it to be so on book-e parts.

>> On 85xx there is no reason to copy the interrupt vectors to low  
>> memory
>> since we can run them in high memory since we are a Book-E core.
>
> High memory means leave them in flash?

No I leave them at the relocated location in DDR.

> Then you will probably see nice crashes as soon as you erase U-Boot
> for example to install a new version.
>
> All references to flash memory must be relocated to RAM, including the
> exception vectors, of course.

Any they are.  I'm just removing a second relocation that is a hold  
over from how 6xx PPC exception vectors work.

>> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
>> ---
>>
>> This is a fix for 1.3.4.
>
> I don't think so. Seems to introduce a bug.

I disagree with that.  It resolved a bug when I did.  'setenv  
autostart no; bootm'

- k

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Wolfgang Denk]

In message <41F2F68F-34F5-4D3B-8AA1-294589B48033@kernel.crashing.org> you wrote:
> 
> > Oops? This is expected and normal behaviour. Did anybody complain
> > about this?
> 
> Real, any reason why?  I understand on classic PPC this might be the  
> case but I see no reason for it to be so on book-e parts.

Well, one reason might be to have identical code for all PPC systems ?

> > High memory means leave them in flash?
> 
> No I leave them at the relocated location in DDR.

Ah, I see.

> > All references to flash memory must be relocated to RAM, including the
> > exception vectors, of course.
> 
> Any they are.  I'm just removing a second relocation that is a hold  
> over from how 6xx PPC exception vectors work.

Not only 6xx. Actually all PPC.

> > I don't think so. Seems to introduce a bug.
> 
> I disagree with that.  It resolved a bug when I did.  'setenv  
> autostart no; bootm'

That might be a problem only when using your broken autostart patches.

We will fix this by backing out that patch ;-)

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
Madness takes its toll. Please have exact change.

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Scott Wood]

On Wed, Aug 06, 2008 at 04:42:51PM +0200, Wolfgang Denk wrote:
> In message <41F2F68F-34F5-4D3B-8AA1-294589B48033@kernel.crashing.org> you wrote:
> > 
> > > Oops? This is expected and normal behaviour. Did anybody complain
> > > about this?

It's hit me before when I foolishly try to load something at address
zero -- why do we put u-boot at the end of RAM, and put up with the
relocation weirdness, if not to allow loading things at zero?

> > Real, any reason why?  I understand on classic PPC this might be the  
> > case but I see no reason for it to be so on book-e parts.
> 
> Well, one reason might be to have identical code for all PPC systems ?

It's already 85xx-specific code.

> > Any they are.  I'm just removing a second relocation that is a hold  
> > over from how 6xx PPC exception vectors work.
> 
> Not only 6xx. Actually all PPC.

No, not all PPC.  Book-E exceptions are different.

-Scott

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Jerry Van Baren]

Scott Wood wrote:
> On Wed, Aug 06, 2008 at 04:42:51PM +0200, Wolfgang Denk wrote:
>> In message <41F2F68F-34F5-4D3B-8AA1-294589B48033@kernel.crashing.org> you wrote:
>>>> Oops? This is expected and normal behaviour. Did anybody complain
>>>> about this?
> 
> It's hit me before when I foolishly try to load something at address
> zero -- why do we put u-boot at the end of RAM, and put up with the
> relocation weirdness, if not to allow loading things at zero?
> 
>>> Real, any reason why?  I understand on classic PPC this might be the  
>>> case but I see no reason for it to be so on book-e parts.
>> Well, one reason might be to have identical code for all PPC systems ?
> 
> It's already 85xx-specific code.
> 
>>> Any they are.  I'm just removing a second relocation that is a hold  
>>> over from how 6xx PPC exception vectors work.
>> Not only 6xx. Actually all PPC.
> 
> No, not all PPC.  Book-E exceptions are different.
> 
> -Scott

One nice thing about not relocating the exception vectors to 0 is that 
it would allow us to recover from a failed bootm all the way up to the 
jump to linux (or whomever) rather than having to reset the board to 
recover from a failure late in the bootm sequence.

Unfortunately, it would be Book-E specific and probably not worth coding 
Yet Another Special Case in the already overcomplex bootm code.

Best regards,
gvb

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Wolfgang Denk]

In message <20080806193205.GA3975@ld0162-tx32.am.freescale.net> you wrote:
>
> It's hit me before when I foolishly try to load something at address
> zero -- why do we put u-boot at the end of RAM, and put up with the
> relocation weirdness, if not to allow loading things at zero?

We want to free as much memory as possible. But low RAM cannot be made
available on all systems.

> > Well, one reason might be to have identical code for all PPC systems ?
> 
> It's already 85xx-specific code.

Good point. Why don't we factor this out and make it common code for
all PPC?

> > Not only 6xx. Actually all PPC.
> 
> No, not all PPC.  Book-E exceptions are different.

Maybe. But then, these can use exception vectors at low mem, too,
right?

For me the chance to have common code (and identical behaviour) for
all PowerPC processors is much more important that being able to use
16 kB additional memory on one specific family of processors.

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
He'd been wrong, there _was_ a light at the end of the tunnel, and it
was a flamethrower.                         - Terry Pratchett, _Mort_

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Kumar Gala]

On Aug 6, 2008, at 2:46 PM, Wolfgang Denk wrote:

> In message <20080806193205.GA3975@ld0162-tx32.am.freescale.net> you  
> wrote:
>>
>> It's hit me before when I foolishly try to load something at address
>> zero -- why do we put u-boot at the end of RAM, and put up with the
>> relocation weirdness, if not to allow loading things at zero?
>
> We want to free as much memory as possible. But low RAM cannot be made
> available on all systems.
>
>>> Well, one reason might be to have identical code for all PPC  
>>> systems ?
>>
>> It's already 85xx-specific code.
>
> Good point. Why don't we factor this out and make it common code for
> all PPC?

Because the relocation is specific to the various interrupt types.   
Book-E will need different code for handing IVPR/IVORs than classic.

>>> Not only 6xx. Actually all PPC.
>>
>> No, not all PPC.  Book-E exceptions are different.
>
> Maybe. But then, these can use exception vectors at low mem, too,
> right?

They can, but it has to be setup.

> For me the chance to have common code (and identical behaviour) for
> all PowerPC processors is much more important that being able to use
> 16 kB additional memory on one specific family of processors.

- k

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Wolfgang Denk]

In message <9D199630-11FA-4028-8EE6-CBC59F6F67A0@kernel.crashing.org> you wrote:
> 
> > Good point. Why don't we factor this out and make it common code for
> > all PPC?
> 
> Because the relocation is specific to the various interrupt types.   
> Book-E will need different code for handing IVPR/IVORs than classic.

Umm... the exception code itself may be different, but does this imply
that the code used to copy / relocate the exception handlers to low
mem must be different, too?

> > Maybe. But then, these can use exception vectors at low mem, too,
> > right?
> 
> They can, but it has to be setup.

What is Linux doing?

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
Life is a game. Money is how we keep score.              - Ted Turner

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Kumar Gala]

On Aug 6, 2008, at 3:17 PM, Wolfgang Denk wrote:

> In message <9D199630-11FA-4028-8EE6- 
> CBC59F6F67A0 at kernel.crashing.org> you wrote:
>>
>>> Good point. Why don't we factor this out and make it common code for
>>> all PPC?
>>
>> Because the relocation is specific to the various interrupt types.
>> Book-E will need different code for handing IVPR/IVORs than classic.
>
> Umm... the exception code itself may be different, but does this imply
> that the code used to copy / relocate the exception handlers to low
> mem must be different, too?

the copying bit should be do-able in generic code.

74xx_7xx/mpc512x/mpc5xx/mpc8xx/mpc8220/mpc824x/mpc83xx/mpc86xx:

copy from [_start, _end_of_vectors] to 0x100

4xx/85xx:

copy from [_start_of_vectors, _end_of_vectors] to 0x100

>>> Maybe. But then, these can use exception vectors at low mem, too,
>>> right?
>>
>> They can, but it has to be setup.
>
> What is Linux doing?

don't follow the question.. what is linux doing with what?

- k

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Wolfgang Denk]

In message <D5CA3AB9-3AE3-439C-A169-F8CD26D4A320@kernel.crashing.org> you wrote:
> 
> >> Book-E will need different code for handing IVPR/IVORs than classic.
> >
> > Umm... the exception code itself may be different, but does this imply
> > that the code used to copy / relocate the exception handlers to low
> > mem must be different, too?
> 
> the copying bit should be do-able in generic code.
> 
> 74xx_7xx/mpc512x/mpc5xx/mpc8xx/mpc8220/mpc824x/mpc83xx/mpc86xx:
> 
> copy from [_start, _end_of_vectors] to 0x100
> 
> 4xx/85xx:
> 
> copy from [_start_of_vectors, _end_of_vectors] to 0x100

OK, that's what I exoected. So we should plan to factor out this part
of code one day.

> >>> Maybe. But then, these can use exception vectors at low mem, too,
> >>> right?
> >>
> >> They can, but it has to be setup.
> >
> > What is Linux doing?
> 
> don't follow the question.. what is linux doing with what?

Where is Linux setting up exception vectors on these systems?

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
"We shall reach greater and greater platitudes of achievement."
- Richard J. Daley

[U-Boot-Users] [PATCH][FOR 1.3.4] 85xx: Don't move interrupt vector to low memory

[Kumar Gala]

On Aug 6, 2008, at 3:41 PM, Wolfgang Denk wrote:

> In message <D5CA3AB9-3AE3-439C-A169- 
> F8CD26D4A320 at kernel.crashing.org> you wrote:
>>
>>>> Book-E will need different code for handing IVPR/IVORs than  
>>>> classic.
>>>
>>> Umm... the exception code itself may be different, but does this  
>>> imply
>>> that the code used to copy / relocate the exception handlers to low
>>> mem must be different, too?
>>
>> the copying bit should be do-able in generic code.
>>
>> 74xx_7xx/mpc512x/mpc5xx/mpc8xx/mpc8220/mpc824x/mpc83xx/mpc86xx:
>>
>> copy from [_start, _end_of_vectors] to 0x100
>>
>> 4xx/85xx:
>>
>> copy from [_start_of_vectors, _end_of_vectors] to 0x100
>
> OK, that's what I exoected. So we should plan to factor out this part
> of code one day.
>
>>>>> Maybe. But then, these can use exception vectors at low mem, too,
>>>>> right?
>>>>
>>>> They can, but it has to be setup.
>>>
>>> What is Linux doing?
>>
>> don't follow the question.. what is linux doing with what?
>
> Where is Linux setting up exception vectors on these systems?

they are at 0 for 6xx/8xx/40x systems.  They can be anywhere on 85xx/ 
44x (and we take advantage of this).

- k