mach header files

[arnd@arndb.de (Arnd Bergmann)]

On Friday 04 April 2014 13:52:53 Phil Edworthy wrote:
> On 04 April 2014 14:24, Arnd wrote:
> > We still make the occasional exception for adding code in the mach-*
> > directory, but we are getting pretty close to the state where this
> > is not needed for new platforms, and all the existing uses are for
> > things that can eventually get cleaned up.
> > If you think you need an exception here, please explain what you
> > are doing, and we can see if there is a better way to do that already.
> 
> Ok, that's what I suspected about the mach header files.
> 
> I didn't realise about the expectation that there is no 
> arch/arm/mach-* for new platforms. At the moment I have only a
> small amount of platform code:
> 1. SMP holding pen code (as there is no power control for the second
> core), though I have recently seen patches to provide a generic solution
> for this.

Proper platforms should not be using the holding pen, that is only
done on systems that don't have real hardware support for CPU
power management. Ideally you should be implementing PSCI in the
firmware, and then you won't need any code for SMP.

> 2. Firmware calls (via struct firmware_ops) for set_cpu_boot_addr
>  and cpu_boot. This falls back to directly accessing registers in
> the system control block, if the firmware fails. This is useful when
> developing the system when no firmware exists yet.

Same thing.

> 3. A write to a system control register to switch the pl011 uart
> from DMA single requests, to DMA burst requests.

Do you need to do this at run-time, or is it something that could
be done in the bootloader before Linux starts up?

	Arnd