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

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Message-ID: <DM6PR12MB30820EE430405FF50C7F856BE8229@DM6PR12MB3082.namprd12.prod.outlook.com>
Date:   Wed, 12 Oct 2022 10:04:09 +0000
From:   "Gupta, Nipun" <Nipun.Gupta@....com>
To:     Marc Zyngier <maz@...nel.org>, Robin Murphy <robin.murphy@....com>
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Subject: RE: [RFC PATCH v3 4/7] bus/cdx: add cdx-MSI domain with gic-its
 domain as parent

[AMD Official Use Only - General]


<snip>

> 
> > +}
> > +
> > +static void cdx_msi_write_msg(struct irq_data *irq_data,
> > +                           struct msi_msg *msg)
> > +{
> > +     /*
> > +      * Do nothing as CDX devices have these pre-populated
> > +      * in the hardware itself.
> > +      */
> 
> We talked about this in a separate thread. This is a major problem.

We discussed this further with the hardware design team and now have the
correct and complete understanding here. As the CDX devices are FPGA based,
they don't exist yet, so it would be possible to construct them in such a way
that the eventid is programable.

To make it generic for CDX devices, we have added a firmware API which provide
the mappings (MSI vector ID to eventID) to the fabric, that can be referred by the
device while generating the MSI interrupt.

Also, there is an existing table to have GITS_TRANSLATOR iova address (address in
msi_msg) for CDX devices, which can be programmed by the firmware. So, providing
IOVA address to device would also not be a problem here.

We would be rolling out RFC v4 with these changes soon.

Regards,
Nipun