From: Jiang Liu <jiang.liu@linux.intel.com>
To: Marc Zyngier <marc.zyngier@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Jason Cooper <jason@lakedaemon.net>
Cc: Ma Jun <majun258@huawei.com>,
linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC 0/7] Adding core support for wire-MSI bridges
Date: Fri, 16 Oct 2015 09:55:35 +0800 [thread overview]
Message-ID: <56205917.7090001@linux.intel.com> (raw)
In-Reply-To: <1444923568-17413-1-git-send-email-marc.zyngier@arm.com>
On 2015/10/15 23:39, Marc Zyngier wrote:
> There seems to be a new class of interrupt controller out there whose
> sole purpose (apart from making everybody's life a nightmare) is to
> turn wired interrupts into MSIs.
>
> Instead of considering that the MSIs allocated to a device are for the
> direct use of that device, we can turn this set of MSIs into a irq
> domain, and use that domain to build a standard irqchip on top of
> that.
Hi Marc,
There's a working to enable Intel VMD storage device, which
has the similar requirement. Basically a PCIe hierarchy is hidden
behind a parent PCIe device, so we need to use the PCIe irqs on parent
to de-multiple PCIe IRQs from hidden PCIe devices. Seems a chance for
consolidation here.
cc Keith Busch <keith.busch@intel.com> who is the author of
VMD device driver.
Thanks!
Gerry
>
> This requires some (slightly ugly) surgery in both the generic MSI and
> platform MSI layers, but the amount of code is actually relatively
> small (about +150 LoC so far).
>
> On top of that, we add a dummy driver for a such a bridge, hoping that
> this will give enough information to driver authors so that they can
> use this new feature. An even more stupid client driver is provided to
> show the interrupt stack allocation:
>
> dummydev dummy-dev: Probing
> dummydev dummy-dev: Allocated IRQ35
> dummydev dummy-dev: Probing OK
> dummydev dummy-dev: IRQ35 hwirq 5 domain msichip_domain_ops
> dummydev dummy-dev: IRQ35 hwirq 0 domain msi_domain_ops
> dummydev dummy-dev: IRQ35 hwirq 8192 domain its_domain_ops
> dummydev dummy-dev: IRQ35 hwirq 8192 domain gic_irq_domain_ops
>
> While this seems to work, it is far from being perfect:
>
> - This is a prototype: error handling is rubbish, and there could be
> better abstractions to use.
>
> - It relies on not declaring this bridge with IRQCHIP_DECLARE in order
> to prevent the DT layer from allocating interrupts behind our back.
>
> - There is some probe ordering issues between the bridge and the wired
> interrupt device, leading to the use of -EPROBE_DEFER.
>
> The last two points could be addressed directly in the OF layer, as
> this is a generic device ordering issue (and people are already
> working on that).
>
> I'd welcome any comment on that approach (though I'm going to make
> myself scarse over the next two weeks).
>
> Marc Zyngier (7):
> platform-msi: Allow MSIs to be allocated in chunks
> platform-msi: Factor out allocation/free of private data
> irqdomain: Make irq_domain_alloc_irqs_recursive available
> genirq/msi: Make the .prepare callback reusable
> genirq/msi: Add msi_domain_populate_irqs
> platform-msi: Allow creation of a MSI-based stacked irq domain
> irqchip: [Example] dummy wired interrupt/MSI bridge driver
>
> drivers/base/platform-msi.c | 185 ++++++++++++++++++++--------
> drivers/irqchip/Kconfig | 7 ++
> drivers/irqchip/Makefile | 1 +
> drivers/irqchip/irq-msichip.c | 271 ++++++++++++++++++++++++++++++++++++++++++
> include/linux/irqdomain.h | 3 +
> include/linux/msi.h | 16 +++
> kernel/irq/irqdomain.c | 6 +-
> kernel/irq/msi.c | 47 +++++++-
> 8 files changed, 481 insertions(+), 55 deletions(-)
> create mode 100644 drivers/irqchip/irq-msichip.c
>
next prev parent reply other threads:[~2015-10-16 1:55 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-15 15:39 [PATCH RFC 0/7] Adding core support for wire-MSI bridges Marc Zyngier
2015-10-15 15:39 ` [PATCH RFC 1/7] platform-msi: Allow MSIs to be allocated in chunks Marc Zyngier
2015-10-15 15:39 ` [PATCH RFC 2/7] platform-msi: Factor out allocation/free of private data Marc Zyngier
2015-10-16 5:46 ` Jiang Liu
2015-10-16 8:50 ` Marc Zyngier
2015-10-15 15:39 ` [PATCH RFC 3/7] irqdomain: Make irq_domain_alloc_irqs_recursive available Marc Zyngier
2015-10-15 15:39 ` [PATCH RFC 4/7] genirq/msi: Make the .prepare callback reusable Marc Zyngier
2015-10-15 17:24 ` Gabriele Paoloni
2015-10-15 17:39 ` Marc Zyngier
2015-10-16 13:07 ` Gabriele Paoloni
2015-10-16 5:45 ` Jiang Liu
2015-10-16 8:48 ` Marc Zyngier
2015-10-15 15:39 ` [PATCH RFC 5/7] genirq/msi: Add msi_domain_populate_irqs Marc Zyngier
2015-10-15 15:39 ` [PATCH RFC 6/7] platform-msi: Allow creation of a MSI-based stacked irq domain Marc Zyngier
2015-10-15 15:39 ` [PATCH RFC 7/7] irqchip: [Example] dummy wired interrupt/MSI bridge driver Marc Zyngier
2015-11-04 8:00 ` majun (F)
2015-11-04 9:03 ` Marc Zyngier
2015-11-05 8:25 ` Gabriele Paoloni
2015-11-05 9:35 ` Marc Zyngier
2015-11-05 9:43 ` Gabriele Paoloni
2015-10-15 15:46 ` [PATCH RFC 0/7] Adding core support for wire-MSI bridges Arnd Bergmann
2015-10-15 16:01 ` Marc Zyngier
2015-10-15 19:16 ` Arnd Bergmann
2015-10-16 8:03 ` Marc Zyngier
2015-10-16 8:45 ` Arnd Bergmann
2015-10-16 1:55 ` Jiang Liu [this message]
2015-10-16 8:48 ` Marc Zyngier
2015-11-04 13:34 ` Thomas Gleixner
2015-11-05 12:22 ` Marc Zyngier
2015-11-05 12:25 ` Thomas Gleixner
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