Re: [RFC][PATCH] m68k/parisc: Convert hp_sdc_rtc driver to rtc framework

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Hi Geert,

Op di 29 jan. 2019 om 10:45 schreef Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>:
On Tue, Jan 29, 2019 at 10:17 AM Kars de Jong <jongk@xxxxxxxxxxxxxx> wrote:
Op ma 28 jan. 2019 om 21:32 schreef Michael Schmitz <schmitzmic@xxxxxxxxx>:
How much RAM does your HP have?

It has 64 MB, so no problems there.

But it is located at the end of the 32-bit address space ;-)

Is HP9000/300 the only platform where that is the case?

As far as I am aware of, yes. At least on m68k.

Digging a bit deeper it turns out that the proposed patch from Roman
(https://marc.info/?l=linux-m68k&m=117184910524555&w=2) that fixed my
problem never made it into the tree.
Since then there have been more changes to
arch/m68k/kernel/mm/motorola.c so that patch probably needs some
changing (and testing on other platforms).

The first two hunks seem to be some safeguards for cases that cannot
happen (memory size must be a multiple of 256 KiB, IIRC, at least on
'020/030). Oh, you had subtracted two from the real size, to avoid wrap
around. Yes, then the memory size is no longer a multiple of 256 KiB.
There may be other places in the kernel where the '020/'030 assumes a
multiple of 256 KiB, so I'd recommend not doing that.

Shouldn't be needed either since I removed the "subtract 1 from size"
from the boot loader already.

The remainder is a fix for address wrap around when there is memory located
at the end of the 32-bit address space.
That part looks OK to me, and is still applicable.

I will retest with just the last part of the patch applied.

Kind regards,

Kars.



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