[PATCH v1 1/2] drivers: firmware: introduce Meson Secure Monitor driver

[Alexey Romanov]

Hello!

On Fri, Jul 07, 2023 at 11:35:47AM -0600, Simon Glass wrote:
> Hi Alexey,
> 
> On Fri, 7 Jul 2023 at 09:43, Alexey Romanov <AVRomanov at sberdevices.ru> wrote:
> >
> > Hello, Simon!
> >
> > On Thu, Jul 06, 2023 at 09:58:02AM -0600, Simon Glass wrote:
> > > Hi Alexey,
> > >
> > > On Thu, 6 Jul 2023 at 14:16, Alexey Romanov <avromanov at sberdevices.ru> wrote:
> > > >
> > > > At the moment, only smc API is a set of functions in
> > > > arch/arm/mach-meson/sm.c. This approach is hard to configure
> > > > and also doesni't contain any generic API for calling smc.
> > > >
> > > > This patch add Meson SM driver with generic API (struct meson_sm_ops):
> > > >
> > > > - sm_call()
> > > > - sm_call_write()
> > > > - sm_call_read()
> > > >
> > > > A typical driver usage example is shown here:
> > > >
> > > > 1. uclass_get_device_by_driver(UCLASS_FIRMWARE, "secure-monitor", &dev);
> > > > 2. handle = meson_sm_get_handle(dev);
> > > > 3. handle->ops.sm_call(dev, cmd, ...);
> > > >
> > > > Signed-off-by: Alexey Romanov <avromanov at sberdevices.ru>
> > > > ---
> > > >  arch/arm/mach-meson/Kconfig       |   1 +
> > > >  drivers/firmware/Kconfig          |  10 ++
> > > >  drivers/firmware/Makefile         |   1 +
> > > >  drivers/firmware/meson/Kconfig    |   6 +
> > > >  drivers/firmware/meson/Makefile   |   3 +
> > > >  drivers/firmware/meson/meson_sm.c | 217 ++++++++++++++++++++++++++++++
> > > >  include/meson/sm_handle.h         |  38 ++++++
> > > >  7 files changed, 276 insertions(+)
> > > >  create mode 100644 drivers/firmware/meson/Kconfig
> > > >  create mode 100644 drivers/firmware/meson/Makefile
> > > >  create mode 100644 drivers/firmware/meson/meson_sm.c
> > > >  create mode 100644 include/meson/sm_handle.h
> > >
> > > Please can you use the remoteproc uclass for this and add a proper driver?
> > >
> >
> > I don't see it architecturally well. Can you explain please?
> >
> > This driver is just ARM SMC fw interface. There seems to be nothing to
> > do here for remoteproc uclass.
> 
> Well you seem to be implementing a remote CPU interface, which is what
> remoteproc is for. How does Linux do this?

The main idea of the patchset is to abstract the smc calls (which run on
the same CPU) and make a request to the firmware that runs on a higher
EL. UCLASS_REMOTEPROC may give the impression that we are
interacting with another CPU, although this is not the case.

Also, UCLASS_REMOTEPROC requires two mandatory interfaces: load() and
start(), and I don't even know how to apply my current changes to them.

My implementation is very close to the Linux implementation, they
also use the firmware driver without remoteproc:

https://elixir.bootlin.com/linux/latest/source/drivers/firmware/meson/meson_sm.c

I spoke to Neil on IRC and he said UCLASS_FIRMWARE for such driver is
OK.

> 
> Also there is a pending series on FFA - is that related? It uses smc
> from what I can tell.

Not entirely clear, my changes don't seem to be related to this
patchset.

> 
> Regards,
> Simon

-- 
Thank you,
Alexey