linux-kernel - Re: [PATCH 0/3] PCI: rockchip: assert PERST# in S3

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Message-ID: <20171013031523.GB25517@bhelgaas-glaptop.roam.corp.google.com>
Date:   Thu, 12 Oct 2017 22:15:23 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, Heiko Stuebner <heiko@...ech.de>,
        linux-pci@...r.kernel.org, Shawn Lin <shawn.lin@...k-chips.com>,
        linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        Rob Herring <robh+dt@...nel.org>,
        Rajat Jain <rajatja@...gle.com>,
        Frank Rowand <frowand.list@...il.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/3] PCI: rockchip: assert PERST# in S3

On Thu, Oct 12, 2017 at 01:52:17PM -0700, Brian Norris wrote:
> Hi,
> 
> This patch series should mostly be self-descriptive, but it's motivated by the
> fact that I've found differing requirements from PCIe endpoint makers regarding
> the state of PERST# when in system suspend (S3). Additionally, some existing
> boards are not especially well suited for holding PERST# low in S3 (e.g., the
> pin is driven by a non-PMU GPIO, so it's hard or impossible to keep it
> asserted). So the solution is...give it a device tree property!

How do ACPI systems solve this problem?

Can you point to any relevant sections in the PCI specs?

Is this a hole in those specs?  Is this something that needs to be
clarified by the PCI-SIG to improve interoperability?

Why is this problem only showing up now?

> Brian Norris (3):
>   Documentation/devicetree: Add pcie-reset-suspend property
>   of/pci: Add of_pci_get_pcie_reset_suspend() to parse
>     pcie-reset-suspend
>   PCI: rockchip: Support configuring PERST# state via DT
> 
>  Documentation/devicetree/bindings/pci/pci.txt | 11 +++++++++++
>  drivers/of/of_pci.c                           | 25 +++++++++++++++++++++++++
>  drivers/pci/host/pcie-rockchip.c              |  7 +++++++
>  include/linux/of_pci.h                        |  7 +++++++
>  4 files changed, 50 insertions(+)
> 
> -- 
> 2.15.0.rc0.271.g36b669edcc-goog
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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