RE: [RFC PATCH v3 4/7] bus/cdx: add cdx-MSI domain with gic-its domain as parent

[Gupta, Nipun]

[AMD Official Use Only - General]



> -----Original Message-----
> From: Marc Zyngier <maz@xxxxxxxxxx>
> Sent: Wednesday, September 7, 2022 6:48 PM
> To: Gupta, Nipun <Nipun.Gupta@xxxxxxx>
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> Subject: Re: [RFC PATCH v3 4/7] bus/cdx: add cdx-MSI domain with gic-its
> domain as parent
> 
> [CAUTION: External Email]
> 
> On Tue, 06 Sep 2022 14:47:58 +0100,
> Nipun Gupta <nipun.gupta@xxxxxxx> wrote:
> >
> > Devices on cdx bus are dynamically detected and registered using
> > platform_device_register API. As these devices are not linked to
> > of node they need a separate MSI domain for handling device ID
> > to be provided to the GIC ITS domain.
> >
> > This also introduces APIs to alloc and free IRQs for CDX domain.
> >
> > Signed-off-by: Nipun Gupta <nipun.gupta@xxxxxxx>
> > Signed-off-by: Nikhil Agarwal <nikhil.agarwal@xxxxxxx>
> > ---
> >  drivers/bus/cdx/cdx.c        |  18 +++
> >  drivers/bus/cdx/cdx.h        |  19 +++
> >  drivers/bus/cdx/cdx_msi.c    | 236
> +++++++++++++++++++++++++++++++++++
> >  drivers/bus/cdx/mcdi_stubs.c |   1 +
> >  include/linux/cdx/cdx_bus.h  |  19 +++
> >  5 files changed, 293 insertions(+)
> >  create mode 100644 drivers/bus/cdx/cdx_msi.c
> >

<..>

> > +             return;
> > +
> > +     msi_domain_free_irqs(msi_domain, dev);
> > +}
> > +EXPORT_SYMBOL(cdx_msi_domain_free_irqs);
> 
> This feels like a very pointless helper, and again a copy/paste from
> the FSL code. I'd rather you change msi_domain_free_irqs() to only
> take a device and use the implicit MSI domain.

I agree with other comments except this one.

In current implementation we have an API "cdx_msi_domain_alloc_irqs()",
so having "cdx_msi_domain_free_irqs()" seems legitimate, as the caller
would allocate and free MSI's using a similar APIs (cdx_msi_domain*).

Changing msi_domain_free_irqs() to use implicit msi domain in case
msi_domain is not provided by the caller seems appropriate, Ill change the
same for "msi_domain_alloc_irqs()" too.

<..>

> > diff --git a/drivers/bus/cdx/mcdi_stubs.c b/drivers/bus/cdx/mcdi_stubs.c
> > index cc9d30fa02f8..2c8db1f5a057 100644
> > --- a/drivers/bus/cdx/mcdi_stubs.c
> > +++ b/drivers/bus/cdx/mcdi_stubs.c
> > @@ -45,6 +45,7 @@ int cdx_mcdi_get_func_config(struct cdx_mcdi_t
> *cdx_mcdi,
> >       dev_params->res_count = 2;
> >
> >       dev_params->req_id = 0x250;
> > +     dev_params->num_msi = 4;
> 
> Why the hardcoded 4? Is that part of the firmware emulation stuff?

Yes, this is currently part of emulation, and would change with proper
emulation support.

> 
>         M.
> 
> --
> Without deviation from the norm, progress is not possible.