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From: Bjorn Helgaas <helgaas@kernel.org>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Duc Dang <dhdang@apm.com>, Rafael Wysocki <rafael@kernel.org>,
	linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org,
	Marc Zyngier <marc.zyngier@arm.com>, patches <patches@apm.com>,
	bhelgaas@google.com, punit.agrawal@arm.com
Subject: Re: Defining polarity and trigger mode for static interrupts in _PRT
Date: Wed, 24 Aug 2016 14:30:00 -0500	[thread overview]
Message-ID: <20160824193000.GE23914@localhost> (raw)
In-Reply-To: <20160824142723.GA25843@red-moon>

On Wed, Aug 24, 2016 at 03:27:23PM +0100, Lorenzo Pieralisi wrote:
> [ +Bjorn, Punit]
> 
> On Wed, Aug 24, 2016 at 04:06:13AM -0700, Duc Dang wrote:
> > [Resend in plain text mode]
> > 
> > Hi Lorenzo, Rafael,
> > 
> > ACPI 6.1 spec does not specify how to set interrupt polarity and
> > trigger mode in _PRT when the interrupts are static (hardwired to
> > specific interrupt inputs in interrupt controller). In current
> > acpi_pci_irq_enable (drivers/acpi/pci_irq.c) implementation, by
> > default the trigger mode is set to LEVEL_SENSITIVE, polarity is set to
> > ACTIVE_LOW. This default setting won't work for ARM64 GICv2, GICv2m,
> > GICv3 controllers and will cause failures in PCIe AER, PME services
> > (on X-Gene platforms).

PCI (not PCIe) r3.0, sec 2.2.6, says "Interrupts on PCI are optional
and defined as 'level sensitive,' asserted low."

I've heard before that ARM64 does this differently, but I still don't
understand the difference.  Obviously if you plug a legacy PCI card
into an ARM64 system, it's still going to pull INTA# low to assert an
interrupt.  So is there something special about ARM64 that inverts
that, or what?

> > Is there any way to specify polarity and trigger mode for static
> > interrupts in _PRT? 

There is no way I'm aware of in _PRT to specify polarity and trigger
mode.  I don't know the history, but my guess is that it would be seen
as superfluous given that the PCI spec requires level, active low.

Obviously I'm missing something important.

Bjorn

  reply	other threads:[~2016-08-24 19:30 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-24 11:06 Defining polarity and trigger mode for static interrupts in _PRT Duc Dang
2016-08-24 14:27 ` Lorenzo Pieralisi
2016-08-24 19:30   ` Bjorn Helgaas [this message]
2016-08-24 20:30     ` Marc Zyngier
2016-08-24 20:30       ` Marc Zyngier
2016-08-24 22:19       ` Duc Dang
2016-08-24 22:56         ` Bjorn Helgaas
2016-08-25 11:18         ` Marc Zyngier
2016-08-25 11:18           ` Marc Zyngier
2016-08-25 16:52           ` Duc Dang
2016-08-25 18:59             ` Marc Zyngier
2016-08-25 18:59               ` Marc Zyngier
2016-08-26  9:08               ` Lorenzo Pieralisi
2016-08-26 11:04                 ` okaya
2016-08-26 12:08                 ` Marc Zyngier
2016-08-26 12:08                   ` Marc Zyngier
2016-08-26 14:07                   ` Sinan Kaya
2016-08-26 17:06                     ` Lorenzo Pieralisi
2016-08-26 22:53                       ` Sinan Kaya
2016-08-30 10:08                         ` Lorenzo Pieralisi
2016-08-30 15:51                           ` Duc Dang
2016-08-30 17:54                             ` Sinan Kaya
2016-08-31 10:07                               ` Lorenzo Pieralisi
2016-08-31 13:05                           ` Bjorn Helgaas
2016-08-31 13:34                             ` Lorenzo Pieralisi
2016-08-31 16:05                               ` Bjorn Helgaas
2016-08-31 16:37                                 ` Lorenzo Pieralisi
2016-08-31 23:08                                   ` Rafael J. Wysocki
2016-09-02 11:09                                     ` Lorenzo Pieralisi
2016-09-02 21:28                                       ` Rafael J. Wysocki
2016-08-25 10:04       ` Punit Agrawal
2016-08-25 10:04         ` Punit Agrawal
2016-08-25 11:14         ` Lorenzo Pieralisi
2016-08-25 16:46           ` Duc Dang
2016-08-25 17:20             ` Bjorn Helgaas
2016-08-24 15:26 ` Marc Zyngier
2016-08-24 15:26   ` Marc Zyngier

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