[PATCH 2/2] platform/ae350: Initialize Coherent Manager as early as possible

[Leo Liang]

On Thu, Sep 23, 2021 at 10:06:34AM +0530, Anup Patel wrote:
> On Thu, Sep 23, 2021 at 8:06 AM Jessica Clarke <jrtc27 at jrtc27.com> wrote:
> >
> > On 23 Sep 2021, at 03:29, Leo Yu-Chi Liang <ycliang at andestech.com> wrote:
> > >
> > > Coherent Manager will guarantee cache coherency as well as
> > > the correctness of atomic extension instruction on Andes 45 series on ae350.
> > >
> > > This feature needs to be enabled before the first
> > > A extension instruction, thus initialize it as early as possible.
> >
> > Why should this be OpenSBI’s responsibility, rather than in whatever
> > firmware you have running before OpenSBI that does whatever low-level
> > platform initialisation is needed like DRAM training (which so far has
> > been kept out of OpenSBI)? This kind of thing makes it impossible to
> > use a generic OpenSBI image, unlike other platforms that have moved
> > towards supporting that. Especially as you explicitly mention U-Boot
> > here, its SPL is the ideal place for this kind of thing, not in OpenSBI.
> 
> I share the same concern. This kind of very early platform specific HART
> initialization makes it impossible for platforms to eventually use generic
> platform firmwares.
> 
> Further, I see that this is being done in the _start() path and not in the
> _start_warm() path so HART hotplug will not be able to do this kind
> of very early platform specific HART initialization.
> 
> Is this for a FPGA platform where there is no booting stage before
> OpenSBI firmware ? If yes then can this very early platform init be
> done in the FPGA boot-up scripts ?
> 
> If there is no other way then I am afraid Andes platform won't benefit
> from generic platform firmwares and Andes will end-up maintaining
> their own OpenSBI platform support.
> 
> Regards,
> Anup
> 

Hi Anup and Jess,

Thanks for the explanation and sorry for forgetting to prepand a RFC
before "PATCH" to clarify this is just a RFC patch.

Yes, we are developing on a FPGA platform without prior boot stage
before OpenSBI, and we can actually do that in a boot up script.

As this kind of approach would draw too much concern, I will drop them.
Thanks again for the comment.

Best regards,
Leo

> >
> > Jess
> >
> >
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