amba, tegra-ahb and pci (Kconfig question)

amba, tegra-ahb and pci (Kconfig question)

[Alessandro Rubini]

Hello.

I plan to submit drivers/amba/apb-pci.c (and later ahb-pci.c), because
the amba-pl011-pci.c I proposed is actually a generic bridge and there
are several such devices in my chip.

I planned to use obj-$(CONFIG_PCI) in drivers/amba/Makefile, but 
commit 87d0bab2cba3c31624b80cc68bcf5e29ef969458 had this in drivers/Makefile:

  -obj-$(CONFIG_ARM_AMBA)         += amba/
  +obj-y                          += amba/

So I ask how to proceed. Shall I define CONFIG_PCI_AMBA or something
like that, or should drivers/amba/tegra-ahb.c be moved to
arch/arm/mach-tegra ?  (I prefer the latter and can submit such patch,
but not without authorization from the involved parties).

If the former (CONFIG_PCI_AMBA), where should the symbol be defined?
My personal preference is doing it like this, plus help message:

   config PCI_AMBA
          bool "PCI-to-AMBA bridge"
          depends on ARM_AMBA && PCI

In this case, shall I name CONFIG_STA2X11 in the depends, or in the
help message, or I'd better be generic, knowing someone else will soon
have similar things?

Thanks
/alessandro

amba, tegra-ahb and pci (Kconfig question)

[Russell King - ARM Linux]

On Mon, May 28, 2012 at 10:17:37AM +0200, Alessandro Rubini wrote:
> If the former (CONFIG_PCI_AMBA), where should the symbol be defined?
> My personal preference is doing it like this, plus help message:
> 
>    config PCI_AMBA
>           bool "PCI-to-AMBA bridge"
>           depends on ARM_AMBA && PCI
> 
> In this case, shall I name CONFIG_STA2X11 in the depends, or in the
> help message, or I'd better be generic, knowing someone else will soon
> have similar things?

Normally, ARM_AMBA is selected when required, so this would be:

config PCI_AMBA
	bool "PCI-to-AMBA bridge"
	depends on PCI
	select ARM_AMBA

I guess I should look at moving ARM_AMBA to drivers/amba/Kconfig too...

amba, tegra-ahb and pci (Kconfig question)

[Alessandro Rubini]

> Normally, ARM_AMBA is selected when required, so this would be:
> 
> config PCI_AMBA
> 	bool "PCI-to-AMBA bridge"
> 	depends on PCI
> 	select ARM_AMBA

But this would open the new question in a zillion boards that are
not interested in it. It's the board that selects arm-amba, in my opinion.
 
> I guess I should look at moving ARM_AMBA to drivers/amba/Kconfig too...

If you want I can submit a patch for this (btw, the rename to primecell
is dead, isn't it?)

thanks
/alessandro

amba, tegra-ahb and pci (Kconfig question)

[Ben Dooks]

On 28/05/12 09:34, Alessandro Rubini wrote:
>> Normally, ARM_AMBA is selected when required, so this would be:
>>
>> config PCI_AMBA
>> 	bool "PCI-to-AMBA bridge"
>> 	depends on PCI
>> 	select ARM_AMBA
>
> But this would open the new question in a zillion boards that are
> not interested in it. It's the board that selects arm-amba, in my opinion.
>
>> I guess I should look at moving ARM_AMBA to drivers/amba/Kconfig too...
>
> If you want I can submit a patch for this (btw, the rename to primecell
> is dead, isn't it?)

Would doing a change from ARM_AMBA to AMBA also be useful, or
adding CONFIG_AMBA and having ARM_AMBA select it?

-- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius

amba, tegra-ahb and pci (Kconfig question)

[Russell King - ARM Linux]

On Mon, May 28, 2012 at 11:23:54AM +0100, Ben Dooks wrote:
> On 28/05/12 09:34, Alessandro Rubini wrote:
>>> Normally, ARM_AMBA is selected when required, so this would be:
>>>
>>> config PCI_AMBA
>>> 	bool "PCI-to-AMBA bridge"
>>> 	depends on PCI
>>> 	select ARM_AMBA
>>
>> But this would open the new question in a zillion boards that are
>> not interested in it. It's the board that selects arm-amba, in my opinion.
>>
>>> I guess I should look at moving ARM_AMBA to drivers/amba/Kconfig too...
>>
>> If you want I can submit a patch for this (btw, the rename to primecell
>> is dead, isn't it?)
>
> Would doing a change from ARM_AMBA to AMBA also be useful, or
> adding CONFIG_AMBA and having ARM_AMBA select it?

Why?  There's nothing wrong with the ARM prefix, because the bus is an
ARM design.  And in any case, if we're considering changing the name
we really should change it to be PRIMECELL and not AMBA - and that is
even more of a reason to keep the ARM_ prefix.

amba, tegra-ahb and pci (Kconfig question)

[Stephen Warren]

On 05/28/2012 02:17 AM, Alessandro Rubini wrote:
> Hello.
> 
> I plan to submit drivers/amba/apb-pci.c (and later ahb-pci.c), because
> the amba-pl011-pci.c I proposed is actually a generic bridge and there
> are several such devices in my chip.
> 
> I planned to use obj-$(CONFIG_PCI) in drivers/amba/Makefile, but 
> commit 87d0bab2cba3c31624b80cc68bcf5e29ef969458 had this in drivers/Makefile:
> 
>   -obj-$(CONFIG_ARM_AMBA)         += amba/
>   +obj-y                          += amba/
> 
> So I ask how to proceed. Shall I define CONFIG_PCI_AMBA or something
> like that, or should drivers/amba/tegra-ahb.c be moved to
> arch/arm/mach-tegra ?  (I prefer the latter and can submit such patch,
> but not without authorization from the involved parties).

FYI, there's a desire to keep all (especially new) drivers out of
arch/arm/mach-*. We had originally wanted to put the tegra-ahb driver in
that directory since it is highly Tegra-specific, but that location was
NAKd.

amba, tegra-ahb and pci (Kconfig question)

[Alessandro Rubini]

> FYI, there's a desire to keep all (especially new) drivers out of
> arch/arm/mach-*. We had originally wanted to put the tegra-ahb driver in
> that directory since it is highly Tegra-specific, but that location was
> NAKd.

Ok. I've seen this trend, actually.  Yesterday I posted the code for
the pci bridge living in drivers/amba besides yours, as Russell
suggested.  I didn't Cc: because it wasn't tegra specific, maybe
I would better have cc'd you.

Thanks
/alessandro