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Re: EDB7312 - Linux booting
On Fri, 2003-02-07 at 08:51, Mark Salter wrote:
> >>>>> Gary Thomas writes:
>
> > On Fri, 2003-02-07 at 04:04, Jonathan Larmour wrote:
> >> Gary Thomas wrote:
> >> > Index: hal/arm/arch/current/src/redboot_linux_exec.c
> >> [snip]
> >> > - params->u.mem.start = CYGARC_PHYSICAL_ADDRESS(CYGMEM_REGION_ram);
> >> > /* Round up so there's only one bit set in the memory size.
> >> > * Don't double it if it's already a power of two, though.
> >> > */
> >> > params->u.mem.size = 1<<hal_msbindex(CYGMEM_REGION_ram_SIZE);
> >> > if (params->u.mem.size < CYGMEM_REGION_ram_SIZE)
> >> > params->u.mem.size <<= 1;
> >> > + params->u.mem.start = CYGARC_PHYSICAL_ADDRESS(CYGMEM_REGION_ram);
> >> > + // Linux doesn't like physical RAM to start on odd boundary
> >> > + params->u.mem.start &= ~(params->u.mem.size-1);
> >>
> >> Excuse my ignorance, but why is this a power of two? Physical memory may
> >> not be a power of two certainly.
>
> > Ask Mark, he wrote this [I think] :-)
>
> You can't pin this one on me! :)
>
> 1.1 (jskov 25-Jan-02): /* Round up so there's only one bit set in the memory size.
> 1.1 (jskov 25-Jan-02): * Don't double it if it's already a power of two, though.
> 1.1 (jskov 25-Jan-02): */
> 1.1 (jskov 25-Jan-02): params->u.mem.size = 1<<hal_msbindex(CYGMEM_REGION_ram_SIZE);
>
> I think what happened was that Jesper copied this code from the original
> ipaq RedBoot code when he made it generic to all arm hals. But Jifl is
> right, not all platforms will have a power of 2 memory size.
>
Forgive me (I didn't check, I just recalled - obviously incorrectly!)
--
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Gary Thomas |
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gpg: http://www.chez-thomas.org/gary/gpg_key.asc
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