Re: [Embedded-pv-devel] [Xen-devel] [PATCH RFC 13/18] xen: introduce and use 'dom0_rambase_pfn' setting for kernel Dom0

["Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxx>]

On Tue, May 31, 2016 at 05:04:42PM +0300, Oleksandr Dmytryshyn wrote:
> On Fri, May 20, 2016 at 7:05 PM, Edgar E. Iglesias
> <edgar.iglesias@xxxxxxxxx> wrote:
> > Hi,
> >
> > We have similar needs (not exactly the same) in some of our setups.
> > We need to map certain OCMs (On Chip Memories) to dom0. Among other things,
> > these are used to communicate with remote accelerators/CPUs that have
> > "hardcoded" addresses to these RAMs.
> >
> > Our approach is more along the lines of Juliens second suggestion. We're
> > trying to use the mmio-sram DTS bindings to bring in these memories into
> > dom0.
> >
> > IIUC the Ducati FW issue correctly, you need to allocate a chunk of DDR.
> >
> > Another possible solution:
> > I think you could reserve the memory area by simply not mentioning it
> > in the main memory node (these nodes support multiple ranges so you can
> > introduce gaps). Then you could for example create an mmio-sram node to
> > get the memory explicitely mapped 1:1 into dom0.
> >
> > Just a moment ago, I posted an RFC for the mmio-sram support to the list.
> Hi, Edgar.
> 
> How do You access to the mapped OCMs in dom0?
> Are genalloc-related functions (gen_pool_get/_alloc/_virt_to_phys)
> only way to work with mmio-sram memory?


Hi Oleksandr,

I'm not familiar enough with the Linux APIs to give a good answer on which
APIs are considered OK and which not.

There are examples in the tree on other ways of using the srams though.
Look for example at this (search for smp-sram):

arch/arm/mach-rockchip/platsmp.c
Documentation/devicetree/bindings/sram/rockchip-smp-sram.txt

The allwinner,sun4i-a10-emac is another example.

Best regards,
Edgar


> 
> > Cheers,
> > Edgar
> >
> >
> >>
> >> Regards,
> >>
> >> [1]
> >> http://lists.xenproject.org/archives/html/xen-devel/2016-05/msg01879.html
> >> [2]
> >> http://lists.xenproject.org/archives/html/xen-devel/2016-05/msg01894.html
> >>
> >> --
> >> Julien Grall
> >>
> >> _______________________________________________
> >> Xen-devel mailing list
> >> Xen-devel@xxxxxxxxxxxxx
> >> http://lists.xen.org/xen-devel

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