Re: [Qemu-devel] [RFC v5 2/5] hw/arm/digic: prepare DIGIC-based boards support

[Antony Pavlov]

On Wed, 4 Dec 2013 20:29:05 +0000
Peter Maydell <address@hidden> wrote:

> On 4 December 2013 20:22, Antony Pavlov <address@hidden> wrote:
> > Here is my proposition:
> >
> > 1. qemu board code setup CPU to start from 0xFFFF0000. (0xffff0000 is a ROM 
> > address
> > on DIGIC chips)
> 
> Sort of. What we need is:
>  1a. Add a "hivecs" property to the ARM CPU object (which
> just sets env->cp15.c1_sys bit 13)
> 
> (this is about half a dozen lines of code max)
> 
>  1b DIGIC board init code creates the CPU and sets the hivecs property on it
> 
> (another handful of lines of code)

Ok, I'll try to make the work at the weekend.

> > 2. we need somehow put a 'jump-to-beginning-of-ROM' instruction to 
> > 0xffff0000.
> > (We can't put barebox to 0xffff0000 as barebox image is bigger that 64K.)
> >
> > There is at least two possibilities to do so:
> >  * we can use specially prepared ROM image;
> >  * qemu board code can insert by itself a 'jump-to-beginning-of-ROM' 
> > instruction
> > after loading ROM image (as qemu MIPS Malta board code does).
> 
> The board code should definitely not be writing random instructions into
> memory. You need to provide a ROM image which will do the work.
> 
> > 3. CPU starts as usual. Branching to barebox code in ROM happends in a 
> > natural way!
> 
> This bit's OK :-)
> 
> thanks
> -- PMM


-- 
-- 
Best regards,
  Antony Pavlov