From: Ray Jui <ray.jui@broadcom.com>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
linux-pci@vger.kernel.org, Tomasz Nowicki <tn@semihalf.com>,
Vladimir Olovyannikov <vladimir.olovyannikov@broadcom.com>,
BCM Kernel Feedback <bcm-kernel-feedback-list@broadcom.com>
Subject: Re: [RFC] ARM64, PCIe, annd ACPI
Date: Wed, 8 Aug 2018 11:49:46 -0700 [thread overview]
Message-ID: <a32a8761-f49f-f0cf-928b-0c323c2b540e@broadcom.com> (raw)
In-Reply-To: <20180808093822.GA25150@e107981-ln.cambridge.arm.com>
On 8/8/2018 2:38 AM, Lorenzo Pieralisi wrote:
> On Tue, Aug 07, 2018 at 05:10:15PM -0700, Ray Jui wrote:
>> Hi Lorenzo/Bjorn,
>>
>> I have a question on PCIe controller APCI support on ARM64 based systems.
>>
>> If my understanding of the implementation of "pci_acpi_scan_root" under
>> "arch/arm64/kernel/pci.c" is correct, it appears
>> "pci_acpi_setup_ecam_mapping" is called within "pci_acpi_scan_root".
>>
>> Does that mean for a PCIe host controller on ARM64 to support ACPI, it needs
>> to support ECAM and MMIO based access to the configuration space registers?
>>
>> If the above statement is true, does it imply that any PCIe controller on
>> ARM64 that does not support MMIO based access to the config space register
>> cannot have ACPI support?
>
> Yes and it is not just MMIO, config space must be ECAM compliant as described
> in the PCI firmware specification and enforced here:
>
> http://infocenter.arm.com/help/topic/com.arm.doc.den0029b/Server_Base_System_Architecture_v5_0_ARM_DEN_0029B.pdf
>
Okay, got it, the SBSA spec makes it very clear that the PCIe controller
needs to support ECAM.
> In short: what's in the mainline (+ adequate PCI controller firmware
> configuration) must be sufficient to bootstrap your PCI subsystem in
> ACPI, it is a very simple litmus test and we won't add anything that
> deviates from that to the mainline kernel ARM64 ACPI PCI code support.
>
It sounds like I'll have to look into ways to work around this at the
driver level as Bjorn pointed out with some other examples.
> Thanks,
> Lorenzo
>
Thanks!
Ray
next prev parent reply other threads:[~2018-08-08 21:10 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-08 0:10 [RFC] ARM64, PCIe, annd ACPI Ray Jui
2018-08-08 2:10 ` Bjorn Helgaas
2018-08-08 18:46 ` Ray Jui
2018-08-08 9:38 ` Lorenzo Pieralisi
2018-08-08 18:49 ` Ray Jui [this message]
2018-08-09 8:59 ` Lorenzo Pieralisi
2018-08-09 14:57 ` Ray Jui
2018-08-09 15:41 ` Lorenzo Pieralisi
2018-08-09 15:44 ` Ray Jui
2018-08-09 16:00 ` Lorenzo Pieralisi
2018-08-09 16:04 ` Ray Jui
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