Modpost warning on Alchemy

Modpost warning on Alchemy

[Ralf Baechle]

Somebody with a clue on the Alchemy stuff may want to look into this
mostpost warning:

  MODPOST vmlinux.o
WARNING: vmlinux.o(.text+0x1e32dc): Section mismatch: reference to .init.text:add_wired_entry (between 'config_access' and 'config_write')
  LD      vmlinux

All the PCI config space accessors on Alchemy will call
arch/mips/pci/ops-au1000.c:config_access which in turn calls add_wired_entry
add_wired_entry in turn is an __init function so it's only a matter of
luck if the PCI code doesn't explode on Alchemy.

So could somebody Alchemist try to rewrite this to use ioremap() instead?

Thanks,

  Ralf

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Ralf Baechle wrote:

> Somebody with a clue on the Alchemy stuff may want to look into this
> mostpost warning:

>   MODPOST vmlinux.o
> WARNING: vmlinux.o(.text+0x1e32dc): Section mismatch: reference to .init.text:add_wired_entry (between 'config_access' and 'config_write')
>   LD      vmlinux

> All the PCI config space accessors on Alchemy will call
> arch/mips/pci/ops-au1000.c:config_access which in turn calls add_wired_entry
> add_wired_entry in turn is an __init function so it's only a matter of
> luck if the PCI code doesn't explode on Alchemy.

> So could somebody Alchemist try to rewrite this to use ioremap() instead?

    Will ioremap() work for 4 GB range? I guess not.
    What actually needs to be done is move this code under if (first_cfg) into 
__init function...

> Thanks,

>   Ralf

MBR, Sergei

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Wed, 1 Aug 2007, Sergei Shtylyov wrote:

> > So could somebody Alchemist try to rewrite this to use ioremap() instead?
> 
>    Will ioremap() work for 4 GB range? I guess not.

 Of course it will.  It shall work with whatever physical address space is 
supported by your MMU.  As long as the MMU is handled correctly that is, 
but I guess I may have omitted this clarification as obvious.

  Maciej

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Maciej W. Rozycki wrote:

>>>So could somebody Alchemist try to rewrite this to use ioremap() instead?

>>   Will ioremap() work for 4 GB range? I guess not.

>  Of course it will.  It shall work with whatever physical address space is 
> supported by your MMU.  As long as the MMU is handled correctly that is, 
> but I guess I may have omitted this clarification as obvious.

    Even on a CPU with 36-bit physical address? ;-)

>   Maciej

WBR, Sergei

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Hello, I wrote:

>>>> So could somebody Alchemist try to rewrite this to use ioremap() 
>>>> instead?

>>>   Will ioremap() work for 4 GB range? I guess not.

>>  Of course it will.  It shall work with whatever physical address 
>> space is supported by your MMU.  As long as the MMU is handled 
>> correctly that is, but I guess I may have omitted this clarification 
>> as obvious.

>    Even on a CPU with 36-bit physical address? ;-)

    WTF... I know I've typed "32-bit CPU"! :-/

>>   Maciej

WBR, Sergei

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Wed, 1 Aug 2007, Sergei Shtylyov wrote:

> > > Of course it will.  It shall work with whatever physical address space is
> > > supported by your MMU.  As long as the MMU is handled correctly that is,
> > > but I guess I may have omitted this clarification as obvious.
> 
> >    Even on a CPU with 36-bit physical address? ;-)
> 
>    WTF... I know I've typed "32-bit CPU"! :-/

 It does not matter.  The physical address of an I/O resource can be 
treated as a cookie that is converted, typically though an MMU, to another 
cookie that can be used with {read,write}{b,w,l}().  Of course you may 
have troubles ioremap()ping say 4GB of I/O space on a processor with a
32-bit virtual address space, but that is a corner case and typically your 
I/O space will be sparsely occupied.

 On a MIPS32 processor you have 512MB of KSEG0/1 unmapped virtual address 
space available for I/O devices located within the first 512MB of the 
physical address space plus 1GB of KSEG2 mapped virtual address space 
available for I/O devices located anywhere in the physical address space.  
That gives you from 1GB to 1.5GB of virtual address space for I/O which is 
enough for all the usual cases.

  Maciej

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Maciej W. Rozycki wrote:

>>>>Of course it will.  It shall work with whatever physical address space is
>>>>supported by your MMU.  As long as the MMU is handled correctly that is,
>>>>but I guess I may have omitted this clarification as obvious.

>>>   Even on a CPU with 36-bit physical address? ;-)

>>   WTF... I know I've typed "32-bit CPU"! :-/

>  It does not matter.  The physical address of an I/O resource can be 

    Believe me, it does in *this* case. :-)

> treated as a cookie that is converted, typically though an MMU, to another 
> cookie that can be used with {read,write}{b,w,l}().  Of course you may 
> have troubles ioremap()ping say 4GB of I/O space on a processor with a
> 32-bit virtual address space, but that is a corner case and typically your 
> I/O space will be sparsely occupied.

    It is exactly this case.

>  On a MIPS32 processor you have 512MB of KSEG0/1 unmapped virtual address 
> space available for I/O devices located within the first 512MB of the 

    PCI config. space is mapped at 0x600000000, well beyond KGSEG0/1.

> physical address space plus 1GB of KSEG2 mapped virtual address space 
> available for I/O devices located anywhere in the physical address space.  
> That gives you from 1GB to 1.5GB of virtual address space for I/O which is 
> enough for all the usual cases.

    This case is not usual. :-)

>   Maciej

    Thanks for wasting time on my education about MIPS. ;-)

WBR, Sergei

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Wed, 1 Aug 2007, Sergei Shtylyov wrote:

>    PCI config. space is mapped at 0x600000000, well beyond KGSEG0/1.

 It is still just fine with ioremap() -- it will simply use KSEG2 in this 
case.  You cannot bypass the TLB here with a 32-bit processor no matter 
what.

 And regarding what you have written above and the size issue you 
mentioned in another e-mail (do you map the whole PCI config space 
linearly in the physical address space of the CPU or suchlike?) -- PCI 
config space accesses are rare (by design rather than chance), so 
performance is a non-issue and it should be absolutely fine for you to 
call ioremap() and iounmap() in code specific for your PCI host bridge for 
the required fragment upon every access.  There is no need for a permanent 
map here.  You probably waste more performance by taking away a TLB entry 
to wire it anyway.

>    Thanks for wasting time on my education about MIPS. ;-)

 Well, more about Linux perhaps than MIPS in general. :-)

  Maciej

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Maciej W. Rozycki wrote:

>>   PCI config. space is mapped at 0x600000000, well beyond KGSEG0/1.

>  It is still just fine with ioremap() -- it will simply use KSEG2 in this 
> case.  You cannot bypass the TLB here with a 32-bit processor no matter 
> what.

>  And regarding what you have written above and the size issue you 
> mentioned in another e-mail (do you map the whole PCI config space 
> linearly in the physical address space of the CPU or suchlike?) -- PCI 

    No, I don't.  But that was why the original code preferred the wired entry 
approach over ioremap() -- not to map a whole range...

> config space accesses are rare (by design rather than chance), so 

    That depends on the drivers used (some IDE drivers access it really often).

> performance is a non-issue and it should be absolutely fine for you to 
> call ioremap() and iounmap() in code specific for your PCI host bridge for 
> the required fragment upon every access.  There is no need for a permanent 

    That's an idea -- however, as the currecnt code uses a cached mapping, 
this part would certainly need to be saved in the new implementaion -- if 
someone will go and fix it eventually. :-)

> map here.  You probably waste more performance by taking away a TLB entry 
> to wire it anyway.

    No, I didn't write that code. :-)

>>   Thanks for wasting time on my education about MIPS. ;-)

>  Well, more about Linux perhaps than MIPS in general. :-)

    Let's say that was about Linux/MIPS.  But the key word was "wasting". ;-)

>   Maciej

WBR, Sergei

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Wed, 1 Aug 2007, Sergei Shtylyov wrote:

> > And regarding what you have written above and the size issue you mentioned
> > in another e-mail (do you map the whole PCI config space linearly in the
> > physical address space of the CPU or suchlike?) -- PCI 
> 
>    No, I don't.  But that was why the original code preferred the wired entry
> approach over ioremap() -- not to map a whole range...

 So what is the issue with the size then?  How big is the area?

> > config space accesses are rare (by design rather than chance), so 
> 
>    That depends on the drivers used (some IDE drivers access it really often).

 It is their problem I would say -- there is a design problem either in 
these drivers or the hardware handled.  The PCI spec is very explicit that 
the config space is meant to be seldom accessed only.  Device 
initialization/shutdown and bus error recovery are the normal places.

> > performance is a non-issue and it should be absolutely fine for you to call
> > ioremap() and iounmap() in code specific for your PCI host bridge for the
> > required fragment upon every access.  There is no need for a permanent 
> 
>    That's an idea -- however, as the currecnt code uses a cached mapping, this
> part would certainly need to be saved in the new implementaion -- if someone
> will go and fix it eventually. :-)

 Well, cached mapping does not seem particularly wise with PCI 
configuration registers, but you have got the ioremap_cachable() call if 
you insist. ;-)

> > Well, more about Linux perhaps than MIPS in general. :-)
> 
>    Let's say that was about Linux/MIPS.  But the key word was "wasting". ;-)

 I reckon the key is how you look at it. ;-)

  Maciej

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Maciej W. Rozycki wrote:

>>>And regarding what you have written above and the size issue you mentioned
>>>in another e-mail (do you map the whole PCI config space linearly in the
>>>physical address space of the CPU or suchlike?) -- PCI 

>>   No, I don't.  But that was why the original code preferred the wired entry
>>approach over ioremap() -- not to map a whole range...

>  So what is the issue with the size then?  How big is the area?

    I've already said: 4 gigs! At least in theory, actually it's 2 gigs due to 
a device # being limited to 0 thru 19 (address bits 11 thru 30 are used as 
IDSELx).

>>>performance is a non-issue and it should be absolutely fine for you to call
>>>ioremap() and iounmap() in code specific for your PCI host bridge for the
>>>required fragment upon every access.  There is no need for a permanent 

>>   That's an idea -- however, as the currecnt code uses a cached mapping, this
>>part would certainly need to be saved in the new implementaion -- if someone
>>will go and fix it eventually. :-)

>  Well, cached mapping does not seem particularly wise with PCI 
> configuration registers, but you have got the ioremap_cachable() call if 
> you insist. ;-)

    I meant that the implementation "caches" the 8 KiB mapping used for the 
last config. access.

>>>Well, more about Linux perhaps than MIPS in general. :-)

>>   Let's say that was about Linux/MIPS.  But the key word was "wasting". ;-)

>  I reckon the key is how you look at it. ;-)

    There was no need to tell me about how KSEG0/1/2 work -- that's why I 
cosidered it wasting time. :-)

>   Maciej

WBR, Sergei

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Wed, 1 Aug 2007, Sergei Shtylyov wrote:

> > So what is the issue with the size then?  How big is the area?
> 
>    I've already said: 4 gigs! At least in theory, actually it's 2 gigs due to

 Oh, I mistook it for the base physical address, sorry.

> a device # being limited to 0 thru 19 (address bits 11 thru 30 are used as
> IDSELx).

 It does not help too much with a 32-bit virtual address space indeed.  
Though I gather it has to be very sparsely populated as 16MiB is enough to 
cover the whole configuration space of a single PCI bus tree.  Thus it has 
to be another example where the chip designer "forgot" to talk to software 
people.  Or a shifter was traded for software performance and complexity. 
;-)

>    I meant that the implementation "caches" the 8 KiB mapping used for the
> last config. access.

 Ah, that can certainly be done with ioremap().

>    There was no need to tell me about how KSEG0/1/2 work -- that's why I
> cosidered it wasting time. :-)

 As I say -- the key is how you look at it.  There are other readers on 
the list who may benefit; it is archived too.  In this sense I can hardly 
consider it a waste of time.  And it was fun to explain and no fun shall 
be ever considered of no use. :-)

  Maciej

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Hello.

Maciej W. Rozycki wrote:

>>>So what is the issue with the size then?  How big is the area?

>>   I've already said: 4 gigs! At least in theory, actually it's 2 gigs due to

>  Oh, I mistook it for the base physical address, sorry.

    That's 24 gigs. :-)

>>a device # being limited to 0 thru 19 (address bits 11 thru 30 are used as
>>IDSELx).

>  It does not help too much with a 32-bit virtual address space indeed.  
> Though I gather it has to be very sparsely populated as 16MiB is enough to 
> cover the whole configuration space of a single PCI bus tree.  Thus it has 

    Hm, maybe 16 MiB would be enough indeed, as the Alchemy CPUs are known to 
not support bus masters behind PCI bridges...

> to be another example where the chip designer "forgot" to talk to software 
> people.  Or a shifter was traded for software performance and complexity. 
> ;-)

    I certainly agree here. :-)

>>   There was no need to tell me about how KSEG0/1/2 work -- that's why I
>>cosidered it wasting time. :-)

>  As I say -- the key is how you look at it.  There are other readers on 
> the list who may benefit; it is archived too.  In this sense I can hardly 
> consider it a waste of time.  And it was fun to explain and no fun shall 
> be ever considered of no use. :-)

    Depends on the source of fun. :-)

>   Maciej

WBR, Sergei

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

Hi,

> > It does not help too much with a 32-bit virtual address space indeed.
> > Though I gather it has to be very sparsely populated as 16MiB is enough to
> > cover the whole configuration space of a single PCI bus tree.  Thus it has 
> 
>    Hm, maybe 16 MiB would be enough indeed, as the Alchemy CPUs are known to
> not support bus masters behind PCI bridges...

 That is unrelated -- for configuration accesses (assuming the basic 
configuration space) you need: 8 bits for the bus number + 5 bits for the 
device number + 3 bits for the function number + 8 bits for the register 
number.  The total is 24 bits.  It is up to hardware to sort it out and 
put the right bits on the bus.

  Maciej

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Maciej W. Rozycki wrote:

>>>It does not help too much with a 32-bit virtual address space indeed.
>>>Though I gather it has to be very sparsely populated as 16MiB is enough to
>>>cover the whole configuration space of a single PCI bus tree.  Thus it has 

>>   Hm, maybe 16 MiB would be enough indeed, as the Alchemy CPUs are known to
>>not support bus masters behind PCI bridges...

>  That is unrelated -- for configuration accesses (assuming the basic 

    I mean who needs crippled subordinate busses? ;-)

> configuration space) you need: 8 bits for the bus number + 5 bits for the 
> device number + 3 bits for the function number + 8 bits for the register 
> number.  The total is 24 bits.

    Yeah, that the format of type 1 cycles.

>  It is up to hardware to sort it out and put the right bits on the bus.

    Unfortunately, Alchemy designers were too lazy to implement a simple 
translation scheme for type 0 cycles. They probably though that with 36-bit 
bus the may not limit themselves... :-)

>   Maciej

WBR, Sergei

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Thu, 2 Aug 2007, Sergei Shtylyov wrote:

>    Yeah, that the format of type 1 cycles.

 Well, that is how it is presented to software on many systems.  The type 
1 cycle format actually differs a little bit, as the two least significant 
bits of the register number are passed to byte enables and when presented 
to the bus they are replaced with a fixed code that denotes the cycle 
type.

>    Unfortunately, Alchemy designers were too lazy to implement a simple
> translation scheme for type 0 cycles. They probably though that with 36-bit
> bus the may not limit themselves... :-)

 Yes, some people seem to think the abundance of resources exempts them 
from properly architecting their designs, sigh...

 On the other hand, the decision to identity-map the PCI config space in 
the physical address space of the processor rather than only making it 
accessible through a pair of an address and a data register was good IMO.

  Maciej

Re: Modpost warning on Alchemy

[Alan Cox]

> >    That depends on the drivers used (some IDE drivers access it really often).
> 
>  It is their problem I would say -- there is a design problem either in 
> these drivers or the hardware handled.  The PCI spec is very explicit that 
> the config space is meant to be seldom accessed only.  Device 
> initialization/shutdown and bus error recovery are the normal places.

An awful lot of vendors get it horribly wrong and many end up needing
configuration space access even in IRQ handlers. Dishonourable mentions
to ATI for example ;)

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Wed, 1 Aug 2007, Alan Cox wrote:

> An awful lot of vendors get it horribly wrong and many end up needing
> configuration space access even in IRQ handlers. Dishonourable mentions
> to ATI for example ;)

 Hmm, wasn't there a host bridge that used bit-banged access to the PCI 
configuration space? ;-)  I have a vague recollection; it might have been 
something else though.

  Maciej

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Sergei Shtylyov wrote:
>>  It is still just fine with ioremap() -- it will simply use KSEG2 in 
>> this case.  You cannot bypass the TLB here with a 32-bit processor no 
>> matter what.

>>  And regarding what you have written above and the size issue you 
>> mentioned in another e-mail (do you map the whole PCI config space 
>> linearly in the physical address space of the CPU or suchlike?) -- PCI 

>    No, I don't.  But that was why the original code preferred the wired 
> entry approach over ioremap() -- not to map a whole range...

    Not the only one: dynamic ioremap() seems to be impossible in interrupt 
context.

>> config space accesses are rare (by design rather than chance), so 

>    That depends on the drivers used (some IDE drivers access it really 
> often).

>> performance is a non-issue and it should be absolutely fine for you to 
>> call ioremap() and iounmap() in code specific for your PCI host bridge 
>> for the required fragment upon every access.  There is no need for a 
>> permanent 

>    That's an idea -- however, as the currecnt code uses a cached 

    No, it seems this actually is not an option. So, the path of least 
resistence should be taken.

WBR, Sergei

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Wed, 1 Aug 2007, Sergei Shtylyov wrote:

> >    No, I don't.  But that was why the original code preferred the wired
> > entry approach over ioremap() -- not to map a whole range...
> 
>    Not the only one: dynamic ioremap() seems to be impossible in interrupt
> context.

 Well, ioremap() may sleep indeed.  How about using a softirq then?  
Broken hardware (=one that requires PCI configuration accesses from the 
IRQ context) is not an excuse to extend the breakage over to software.

  Maciej

Re: Modpost warning on Alchemy

[Ralf Baechle]

On Thu, Aug 02, 2007 at 10:39:21AM +0100, Maciej W. Rozycki wrote:

> > >    No, I don't.  But that was why the original code preferred the wired
> > > entry approach over ioremap() -- not to map a whole range...
> > 
> >    Not the only one: dynamic ioremap() seems to be impossible in interrupt
> > context.
> 
>  Well, ioremap() may sleep indeed.  How about using a softirq then?  
> Broken hardware (=one that requires PCI configuration accesses from the 
> IRQ context) is not an excuse to extend the breakage over to software.

Lockdep would trigger on ioremap from an interrupt almost immediately.
But I guess not a whole lot of people are using it, probably because they
think they're safe from locking problems on uniprocessors ...

  Ralf

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Thu, 2 Aug 2007, Ralf Baechle wrote:

> Lockdep would trigger on ioremap from an interrupt almost immediately.
> But I guess not a whole lot of people are using it, probably because they
> think they're safe from locking problems on uniprocessors ...

 Either this or they are not aware of its existence. ;-)

  Maciej

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Maciej W. Rozycki wrote:

>>>   No, I don't.  But that was why the original code preferred the wired
>>>entry approach over ioremap() -- not to map a whole range...

>>   Not the only one: dynamic ioremap() seems to be impossible in interrupt
>>context.

>  Well, ioremap() may sleep indeed.

    So, the only viable option of using sofirq() is mapping all the sparce 
2KiB regions at the __init time -- that will waste every half of page though...

>  How about using a softirq then?  

    Using softirq for what?

> Broken hardware (=one that requires PCI configuration accesses from the 
> IRQ context) is not an excuse to extend the breakage over to software.

    That's *at least* impractical argument.

>   Maciej

WBR, Sergei

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Hi, I wrote:

>>>>   No, I don't.  But that was why the original code preferred the wired
>>>> entry approach over ioremap() -- not to map a whole range...

>>>   Not the only one: dynamic ioremap() seems to be impossible in 
>>> interrupt
>>> context.

>>  Well, ioremap() may sleep indeed.

>    So, the only viable option of using sofirq() is mapping all the 
> sparce 2KiB regions at the __init time -- that will waste every half of 
> page though...

    That for the root PCI bus and 16 megs at 0x680000000 for the subordinates.

WBR, Sergei

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Thu, 2 Aug 2007, Sergei Shtylyov wrote:

> > How about using a softirq then?  
> 
>    Using softirq for what?

 For what you would otherwise want to do in the interrupt context.

 If you want an example, then please have a look at phylib, where in the 
interrupt handler you cannot even access the interrupt status register of 
the originating device (there may be a number of them sharing the same 
line too), because in general it is impossible to access the MDIO bus from 
the interrupt context.

  Maciej

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Maciej W. Rozycki wrote:

>>>How about using a softirq then?  

>>   Using softirq for what?

>  For what you would otherwise want to do in the interrupt context.

>  If you want an example, then please have a look at phylib, where in the 

    No.  I don't feel like rewriting IDE/libata cores. ;-)

> interrupt handler you cannot even access the interrupt status register of 
> the originating device (there may be a number of them sharing the same 
> line too), because in general it is impossible to access the MDIO bus from 
> the interrupt context.

    Thanks for the example, though.

>   Maciej

MBR, Sergei

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Thu, 2 Aug 2007, Sergei Shtylyov wrote:

> > If you want an example, then please have a look at phylib, where in the 
> 
>    No.  I don't feel like rewriting IDE/libata cores. ;-)

 Apparently nobody does, but the lone idea of some code out there to do 
all the PIO transfers in the interrupt context does not seem terribly 
fortunate.  Other bits like this may benefit as a side effect.

  Maciej

Re: Modpost warning on Alchemy

[Alan Cox]

On Wed, 01 Aug 2007 17:13:15 +0400
Sergei Shtylyov <sshtylyov@ru.mvista.com> wrote:

> Maciej W. Rozycki wrote:
> 
> >>>So could somebody Alchemist try to rewrite this to use ioremap() instead?
> 
> >>   Will ioremap() work for 4 GB range? I guess not.
> 
> >  Of course it will.  It shall work with whatever physical address space is 
> > supported by your MMU.  As long as the MMU is handled correctly that is, 
> > but I guess I may have omitted this clarification as obvious.
> 
>     Even on a CPU with 36-bit physical address? ;-)

Nope. This is one problem for example with ioremap on a Pentium Pro.

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Wed, 1 Aug 2007, Alan Cox wrote:

> > >  Of course it will.  It shall work with whatever physical address space is 
> > > supported by your MMU.  As long as the MMU is handled correctly that is, 
> > > but I guess I may have omitted this clarification as obvious.
> > 
> >     Even on a CPU with 36-bit physical address? ;-)
> 
> Nope. This is one problem for example with ioremap on a Pentium Pro.

 Well, but we only consider MIPS processors here which do not have such 
odd restrictions resulting from bad design decisions in the past. ;-)  
The 32-bit TLB entry format allows for up to 36 bits of the physical 
address space (34 bits if support for the page size of 1kB has been 
enabled).  For anything beyond that you need a 64-bit MIPS processor using 
the 64-bit TLB entry format.

  Maciej

Re: Modpost warning on Alchemy

[Alan Cox]

> > >     Even on a CPU with 36-bit physical address? ;-)
> > 
> > Nope. This is one problem for example with ioremap on a Pentium Pro.
> 
>  Well, but we only consider MIPS processors here which do not have such 
> odd restrictions resulting from bad design decisions in the past. ;-)  
> The 32-bit TLB entry format allows for up to 36 bits of the physical 
> address space (34 bits if support for the page size of 1kB has been 

So does the Pentium Pro. We can map 36bit physical addresses.

> enabled).  For anything beyond that you need a 64-bit MIPS processor using 
> the 64-bit TLB entry format.

Your problem is a little higher up the stack. ioremap takes an unsigned
long, which on a 32bit system usually means you can't give it a 36bit bus
address to remap.

Alan

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Wed, 1 Aug 2007, Alan Cox wrote:

> > enabled).  For anything beyond that you need a 64-bit MIPS processor using 
> > the 64-bit TLB entry format.
> 
> Your problem is a little higher up the stack. ioremap takes an unsigned
> long, which on a 32bit system usually means you can't give it a 36bit bus
> address to remap.

 Well, phys_t is what it takes for MIPS and for MIPS:

#ifdef CONFIG_64BIT_PHYS_ADDR
typedef unsigned long long phys_t;
#else
typedef unsigned long phys_t;
#endif

so no problem here as long as you enable CONFIG_64BIT_PHYS_ADDR which is 
implied in such a case.

  Maciej

Re: Modpost warning on Alchemy

[Ralf Baechle]

On Wed, Aug 01, 2007 at 05:00:21PM +0100, Maciej W. Rozycki wrote:

> #ifdef CONFIG_64BIT_PHYS_ADDR
> typedef unsigned long long phys_t;
> #else
> typedef unsigned long phys_t;
> #endif
> 
> so no problem here as long as you enable CONFIG_64BIT_PHYS_ADDR which is 
> implied in such a case.

Which happens to be the solution that is Linus-incompatible so I may
eventually have to change it ;-)

  Ralf

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Wed, 1 Aug 2007, Ralf Baechle wrote:

> > so no problem here as long as you enable CONFIG_64BIT_PHYS_ADDR which is 
> > implied in such a case.
> 
> Which happens to be the solution that is Linus-incompatible so I may
> eventually have to change it ;-)

 Well, however we do it, the width of the physical address cookie used 
with ioremap() should not be forced to be related to the width of the 
virtual address space in any way.  I see no reason for us to be crippled 
by limitations of some other architectures or, worse yet, by ones of some 
code specific to some other platform.

  Maciej

Re: Modpost warning on Alchemy

[Ralf Baechle]

On Wed, Aug 01, 2007 at 05:33:25PM +0100, Maciej W. Rozycki wrote:

> > Which happens to be the solution that is Linus-incompatible so I may
> > eventually have to change it ;-)
> 
>  Well, however we do it, the width of the physical address cookie used 
> with ioremap() should not be forced to be related to the width of the 
> virtual address space in any way.  I see no reason for us to be crippled 
> by limitations of some other architectures or, worse yet, by ones of some 
> code specific to some other platform.

It's the physical not virtual address and as you say yourself it's a cookie
so could potencially be some opaque value that isn't a physical address
at all.  And I wouldn't quite call it crippling that's certainly way
exagerated.

  Ralf

Re: Modpost warning on Alchemy

[Maciej W. Rozycki]

On Thu, 2 Aug 2007, Ralf Baechle wrote:

> It's the physical not virtual address and as you say yourself it's a cookie
> so could potencially be some opaque value that isn't a physical address
> at all.  And I wouldn't quite call it crippling that's certainly way
> exagerated.

 Well, once you start hashing your physical addresses into smaller cookies 
you ask for complexity and likely trouble.  But it should be doable -- you 
cannot map more of the physical space at a time than you can address 
virtually.

  Maciej

Re: Modpost warning on Alchemy

[Sergei Shtylyov]

Alan Cox wrote:

>>>>    Even on a CPU with 36-bit physical address? ;-)

>>>Nope. This is one problem for example with ioremap on a Pentium Pro.

>> Well, but we only consider MIPS processors here which do not have such 
>>odd restrictions resulting from bad design decisions in the past. ;-)  
>>The 32-bit TLB entry format allows for up to 36 bits of the physical 
>>address space (34 bits if support for the page size of 1kB has been 

> So does the Pentium Pro. We can map 36bit physical addresses.

>>enabled).  For anything beyond that you need a 64-bit MIPS processor using 
>>the 64-bit TLB entry format.

> Your problem is a little higher up the stack. ioremap takes an unsigned
> long, which on a 32bit system usually means you can't give it a 36bit bus
> address to remap.

    It takes phys_t, which is 'unsigned long long' for this platform that has 
CONFIG_64BUIT_PHYS_ADDR=y. The reall issue is the size.

> Alan

WBR, Sergei