Amba device porting

Amba device porting

[Roman]

Hi,

I planned to port the omap3 SDTI (Serial Debug Trace Interface) driver to amba based interface.

SDTI memory map is two parts composed:
0x54500000 0x5450FFFF 4KB       SDTI module (configuration) - coresight based format.
0x54510000 0x545FFFFF 1984KB    Reserved
0x54600000 0x546FFFFF 1MB       SDTI module (window)

But amba interface seems to support only one memory region resource.

Is there any way to pass two memory regions?


Regards
Roman Tereshonkov

Re: Amba device porting

[Russell King - ARM Linux]

On Wed, Dec 23, 2009 at 12:19:02PM +0200, Roman wrote:
> Hi,
> 
> I planned to port the omap3 SDTI (Serial Debug Trace Interface) driver to amba based interface.
> 
> SDTI memory map is two parts composed:
> 0x54500000 0x5450FFFF 4KB       SDTI module (configuration) - coresight based format.
> 0x54510000 0x545FFFFF 1984KB    Reserved
> 0x54600000 0x546FFFFF 1MB       SDTI module (window)
> 
> But amba interface seems to support only one memory region resource.

The 'amba' interface is more a primecell interface.  Is SDTI a primecell
peripheral?  If not, then it shouldn't be using the AMBA "primecell" bus
support.

Re: Amba device porting

[Roman]

On Wed, Dec 23, 2009 at 05:50:09PM +0100, ext Russell King - ARM Linux wrote:
> On Wed, Dec 23, 2009 at 12:19:02PM +0200, Roman wrote:
> > Hi,
> > 
> > I planned to port the omap3 SDTI (Serial Debug Trace Interface) driver to amba based interface.
> > 
> > SDTI memory map is two parts composed:
> > 0x54500000 0x5450FFFF 4KB       SDTI module (configuration) - coresight based format.
> > 0x54510000 0x545FFFFF 1984KB    Reserved
> > 0x54600000 0x546FFFFF 1MB       SDTI module (window)
> > 
> > But amba interface seems to support only one memory region resource.
> 
> The 'amba' interface is more a primecell interface.  Is SDTI a primecell
> peripheral?  If not, then it shouldn't be using the AMBA "primecell" bus
> support.

Yes, SDTI can be considered as a PrimeCell IP.
SDTI is the Coresight component which is the subgroup of PrimeCell.

So my question is still valid.
How does the 'amba' interface handle the fragmented memory regions?
I understand that for the right Coresight IP it should not happen and the whole register space should be continous and ended by the Peripherial and Component Ids.
If I use SDTI module (window) memory region as a static definition inside driver will my patch be accepted?


Regards
Roman Tereshonkov

Re: Amba device porting

[Russell King - ARM Linux]

On Mon, Dec 28, 2009 at 01:02:25PM +0200, Roman wrote:
> On Wed, Dec 23, 2009 at 05:50:09PM +0100, ext Russell King - ARM Linux wrote:
> > On Wed, Dec 23, 2009 at 12:19:02PM +0200, Roman wrote:
> > > Hi,
> > > 
> > > I planned to port the omap3 SDTI (Serial Debug Trace Interface) driver to amba based interface.
> > > 
> > > SDTI memory map is two parts composed:
> > > 0x54500000 0x5450FFFF 4KB       SDTI module (configuration) - coresight based format.
> > > 0x54510000 0x545FFFFF 1984KB    Reserved
> > > 0x54600000 0x546FFFFF 1MB       SDTI module (window)
> > > 
> > > But amba interface seems to support only one memory region resource.
> > 
> > The 'amba' interface is more a primecell interface.  Is SDTI a primecell
> > peripheral?  If not, then it shouldn't be using the AMBA "primecell" bus
> > support.
> 
> Yes, SDTI can be considered as a PrimeCell IP.
> SDTI is the Coresight component which is the subgroup of PrimeCell.
> 
> So my question is still valid.
> How does the 'amba' interface handle the fragmented memory regions?

It doesn't.  Primecells have exactly one region and only one region.
So I'm confused.

> I understand that for the right Coresight IP it should not happen and the
> whole register space should be continous and ended by the Peripherial and
> Component Ids.

Correct.  It could be that this Coresight stuff just calls itself a
Primecell peripheral when it isn't actually a proper Primecell.  If
it doesn't conform, maybe it's best that it doesn't use the AMBA bus
support.

> If I use SDTI module (window) memory region as a static definition inside
> driver will my patch be accepted?

That ties it firmly to the platform you created the driver for, making
the driver useless on any other platform.