From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: Re: [PATCH] drivers: acpi: fix GIC irq model default PCI IRQ polarity Date: Mon, 5 Sep 2016 15:32:01 +0100 Message-ID: <57CD81E1.4090705@arm.com> References: <1473084758-7377-1-git-send-email-lorenzo.pieralisi@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from foss.arm.com ([217.140.101.70]:58054 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755307AbcIEOcJ (ORCPT ); Mon, 5 Sep 2016 10:32:09 -0400 In-Reply-To: <1473084758-7377-1-git-send-email-lorenzo.pieralisi@arm.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Lorenzo Pieralisi , linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, Punit Agrawal , Duc Dang , Bjorn Helgaas , Sinan Kaya , "Rafael J. Wysocki" On 05/09/16 15:12, Lorenzo Pieralisi wrote: > On ACPI ARM based systems the GIC interrupt controller > and corresponding interrupt model permit only the high > polarity for level interrupts. > > ACPI firmware describes PCI legacy IRQs through entries > in the _PRT objects. Entries in the _PRT can be of two types: > > - Static: not configurable, trigger/polarity default to level-low, > _PRT entry defines the global GSI interrupt number > - Configurable: _PRT interrupt entry contains a reference to the > corresponding PCI interrupt link device (that in turn provides the > interrupt descriptor through its _CRS/_PRS methods) > > Configurable IRQ entries are not currently allowed by the ACPI > specification on ARM, since they can only be used for interrupt > pins that are routable, and ARM platforms GIC configurations > do not allow dynamic IRQ routing, routing is statically laid out > at synthesis time; therefore PCI interrupt links cannot be used > for PCI legacy IRQ descriptions in the _PRT on ARM systems. > > On the other hand, current core ACPI code handling PCI legacy IRQs > consider IRQ trigger/polarity for static _PRT entries as level-low. > > On ARM systems with a GIC interrupt controller and corresponding > ACPI interrupt model this does not work in that GIC interrupt > controller is only capable of handling level interrupts whose > polarity is high (for PCI legacy IRQs - that are level-low by > specification - this means that the legacy IRQs are inverted before > reaching the interrupt controller pin), resulting in IRQ allocation > failures such as: > > genirq: Setting trigger mode 8 for irq 18 failed (gic_set_type+0x0/0x48) > > Change the default polarity for PCI legacy IRQs to high on systems > booting wth ACPI on platforms with a GIC interrupt controller model, > fixing the discrepancy between specification and HW behaviour. > > Signed-off-by: Lorenzo Pieralisi > Cc: Punit Agrawal > Cc: Duc Dang > Cc: Bjorn Helgaas > Cc: Sinan Kaya > Cc: "Rafael J. Wysocki" > Cc: Marc Zyngier > --- > drivers/acpi/pci_irq.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c > index 2c45dd3..c576a6f 100644 > --- a/drivers/acpi/pci_irq.c > +++ b/drivers/acpi/pci_irq.c > @@ -411,7 +411,15 @@ int acpi_pci_irq_enable(struct pci_dev *dev) > int gsi; > u8 pin; > int triggering = ACPI_LEVEL_SENSITIVE; > - int polarity = ACPI_ACTIVE_LOW; > + /* > + * On ARM systems with the GIC interrupt model, level interrupts > + * are always polarity high by specification; PCI legacy > + * IRQs lines are inverted before reaching the interrupt > + * controller and must therefore be considered active high > + * as default. > + */ > + int polarity = acpi_irq_model == ACPI_IRQ_MODEL_GIC ? > + ACPI_ACTIVE_HIGH : ACPI_ACTIVE_LOW; > char *link = NULL; > char link_desc[16]; > int rc; > Acked-by: Marc Zyngier M. -- Jazz is not dead. It just smells funny...