linux-kernel - Re: [PATCH v2 3/3] irqchip/gicv3-its: Handle OF device tree "msi-map" properties.

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Message-ID: <20150923175259.GT7356@arm.com>
Date:	Wed, 23 Sep 2015 18:52:59 +0100
From:	Will Deacon <will.deacon@....com>
To:	David Daney <ddaney@...iumnetworks.com>
Cc:	Marc Zyngier <Marc.Zyngier@....com>,
	David Daney <ddaney.cavm@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH v2 3/3] irqchip/gicv3-its:  Handle OF device tree
 "msi-map" properties.

On Wed, Sep 23, 2015 at 06:08:39PM +0100, David Daney wrote:
> On 09/23/2015 10:01 AM, Marc Zyngier wrote:
> > On Tue, 22 Sep 2015 17:00:06 -0700
> > David Daney <ddaney.cavm@...il.com> wrote:
> >
> >> From: David Daney <david.daney@...ium.com>
> >>
> >> Call of_msi_map_rid() to handle mapping of the requester id.
> >>
> >> Signed-off-by: David Daney <david.daney@...ium.com>
> >> ---
> >>   drivers/irqchip/irq-gic-v3-its-pci-msi.c | 3 ++-
> >>   1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/irqchip/irq-gic-v3-its-pci-msi.c b/drivers/irqchip/irq-gic-v3-its-pci-msi.c
> >> index cf351c6..8b1c938 100644
> >> --- a/drivers/irqchip/irq-gic-v3-its-pci-msi.c
> >> +++ b/drivers/irqchip/irq-gic-v3-its-pci-msi.c
> >> @@ -86,7 +86,8 @@ static int its_pci_msi_prepare(struct irq_domain *domain, struct device *dev,
> >>   	pci_for_each_dma_alias(pdev, its_get_pci_alias, &dev_alias);
> >>
> >>   	/* ITS specific DeviceID, as the core ITS ignores dev. */
> >> -	info->scratchpad[0].ul = dev_alias.dev_id;
> >> +	info->scratchpad[0].ul = of_msi_map_rid(dev, domain->of_node,
> >> +						dev_alias.dev_id);
> >>
> >>   	return msi_info->ops->msi_prepare(domain->parent,
> >>   					  dev, dev_alias.count, info);
> >
> > I really wonder if that shouldn't be part of the pci_for_each_dma_alias
> > call. It would make a lot more sense for this functionality to be an
> > integral part of the core code, and would probably make the integration
> > of _IORT (which has the exact same requirements) a bit easier.
> >
> > Thoughts?
> >
> 
> I am a proponent of pushing things like this as far into the core code 
> as possible.  So, from that point of view, I think it would probably be 
> a good idea.
> 
> I can prepare a patch that does that, but it would also be nice hear 
> from other maintainers and get their thoughts on this.

Hmm, we use pci_for_each_dma_alias in the SMMU drivers to get the SID,
so I'm not sure that using the MSI mapping is necessarily the right thing
to do there. Maybe we should instead have dma_alias_to_msi_id helpers or
something?

Will
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