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From:   Pierre Gondois <pierre.gondois@arm.com>
To:     linux-kernel@vger.kernel.org
Cc:     Bjorn Helgaas <bhelgaas@google.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>, linux-pci@vger.kernel.org,
        linux-acpi@vger.kernel.org
Subject: [PATCH RESEND v1 0/2] Make _PRS and _SRS methods optional
Date:   Fri,  1 Jul 2022 18:16:22 +0200
Message-Id: <20220701161624.2844305-1-pierre.gondois@arm.com>
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The PCI legacy interrupts can be described with link devices,
cf ACPI 6.4, s6.2.13 "_PRT (PCI Routing Table)".
Link devices can have optional _SRS/_PRS methods to set the interrupt.

In PCI Firmware Specification Revision 3.3, s4.3.2.1. "Resource Setting":
"""
A non-configurable device only specifies _CRS. However, if they are
configurable, devices include _PRS to indicate the possible resource
setting and _SRS to allow OSPM to specify a new resource allocation
for the device.
"""

However, _PRS/_SRS methods are checked in drivers/acpi/pci_link.c,
and the driver aborts if they are absent.
E.g.: When _PRS is missing:
ACPI: \_SB_.PCI0.LNKA: _CRS 36 not found in _PRS
ACPI: \_SB_.PCI0.LNKA: No IRQ available. Try pci=noacpi or acpi=off

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215560

Pierre Gondois (2):
  ACPI/PCI: Make _SRS optional for link device
  ACPI/PCI: Make _PRS optional for link device

 drivers/acpi/pci_link.c | 46 ++++++++++++++++++++++++++++-------------
 1 file changed, 32 insertions(+), 14 deletions(-)

-- 
2.25.1