Re: [PATCH v16 6/6] soc: amd: Add support for AMD Pensando SoC Controller

Andy Shevchenko
2023-09-25T08:52:29Z

On Fri, Sep 22, 2023 at 1:24 PM Arnd Bergmann <arnd@arndb.de> wrote:
> On Wed, Sep 13, 2023, at 17:49, Brad Larson wrote:

...

> > v15 changes:
> > - Drop custom ioctl and use existing miscdevice interface.
> > - Delete unused definitions in amd-pensando-ctrl.h
> > - Makefile change to compile for ARCH_PENSANDO
>
> Hi Brad,
>
> I'm sorry I've been out of the loop for so long, and I hope
> we can find a way to manage your SoC support soon. My impression
> is that the normal support patches (1, 3, 4, and 5) are largely
> uncontroversial, while the SoC controller support seems like
> we are still not converging onto something that is ready to
> merge, so I would suggest you split the two parts and send
> the basic support for inclusion in linux-6.7 while we continue
> to discuss the soc controller driver.
>
> Please remove any references to the soc controller from the
> dts files and send that first series to:soc@kernel.org
> cc:linux-arm-kernel (and the other interested parties) so
> I can pick those up.
>
> Regarding the soc controller driver, let me try to give
> you my impression of where we are:
>
> - you have gone through 16 revisions already, which is way
> too much for a public review, we should have been able
> to find a solution earlier than that, and this is partly
> our fault on the reviewer side, and I'm sorry about that.
>
> - Andy's latest comments and a lot of the earlier reviews
> were focused on implementation details. While those comments
> are helpful suggestions for improving the code, they miss
> the larger point about the system design that I'm worried
> about and probably don't help you actually get it merged.

True. The fact that the new versions left the design remaining make me
think that the ABI was settled down.

> - The main problem I still see is that this driver completely
> bypasses our normal kernel abstractions and instead creates
> a low-level passthrough interface for handling kernel
> functionality in userspace. This creates a liability both
> for the user ABI and the kernel implementation and prevents
> any
>
> - There is a chance that your design is in fact the
> best way to handle this particular hardware, but it is
> your job to write a convincing explanation of why this
> platform is different from all the others in the patch
> description. Your current one-paragraph text does not
> explain this at all.
>
> I would suggest you prioritize getting the other patches
> included for the moment, but we can keep discussion the
> API design for this driver either in this thread or on the
> #armlinux IRC channel (irc.libera.chat) in parallel if you
> like. In order to help you here, I would need either
> the documentation of the SPI software interface, or the
> source code for the userspace tool.

--
With Best Regards,
Andy Shevchenko