[U-Boot] [PATCH] riscv: cpu: Skip unavailable hart in the get_count() op

Auer, Lukas lukas.auer at aisec.fraunhofer.de
Thu Aug 8 14:03:39 UTC 2019

Hi Bin,

On Thu, 2019-08-08 at 21:25 +0800, Bin Meng wrote:
> Hi Lukas,
> On Thu, Aug 8, 2019 at 7:22 PM Auer, Lukas
> <lukas.auer at aisec.fraunhofer.de> wrote:
> > Hi Bin,
> > 
> > On Thu, 2019-08-08 at 00:52 -0700, Bin Meng wrote:
> > > We should not count in hart that is marked as not available in the
> > > device tree in riscv_cpu_get_count().
> > > 
> > 
> > I think it might make sense to also exclude harts that are not listed
> > as available in the available_harts mask. So the same logic as in
> > arch/riscv/lib/smp.c. In this case, the bind function should probably
> > check the mask as well.
> > 
> Yes, the check to available_harts mask can be added in
> riscv_cpu_get_count(). I will do that.
> However, I doubt we could do available_harts mask check in the bind
> function. If it returns error for non-available harts, the whole
> initialization process fails.

You are right, I did not think about that. Perhaps it's best to ignore
the available_harts mask in the count function as well then.

It just checked where cpu_get_count() is used. The Andes PLIC driver
(lib/andes_plic.c) uses it in a way that the patch might break the
driver. It iterates over all harts, assuming the first hart is 0 and
the last hart the result of cpu_get_count(). If any of the harts is set
to disabled, this will no longer be true. It's probably best to update
the driver to use the ofnode_for_each_subnode() macro to iterate over
all harts. Rick, can you update the driver?


> > Looks good otherwise!
> > 
> > Reviewed-by: Lukas Auer <lukas.auer at aisec.fraunhofer.de>
> > 
> Regards,
> Bin

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