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

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Message-ID: <20150923191834.1764ca02@arm.com>
Date:	Wed, 23 Sep 2015 19:18:34 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Will Deacon <will.deacon@....com>
Cc:	David Daney <ddaney@...iumnetworks.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, 23 Sep 2015 18:52:59 +0100
Will Deacon <will.deacon@....com> wrote:

> 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?

Yes, that's probably a sensible solution.

	M.
-- 
Jazz is not dead. It just smells funny.
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