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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jiang Liu <liuj97@gmail.com>, Jiang Liu <jiang.liu@huawei.com>,
        Yinghai Lu <yinghai@kernel.org>,
        Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>,
        Yijing Wang <wangyijing@huawei.com>, linux-kernel@vger.kernel.org,
        linux-pci@vger.kernel.org,
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        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Toshi Kani <toshi.kani@hp.com>, Myron Stowe <myron.stowe@redhat.com>
Subject: Re: [RFC PATCH v5 7/8] PCI/PCIe: add "pci=nopciehp" to disable PCIe native hotplug
Date: Fri, 18 Jan 2013 23:01:16 +0100
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On Friday, January 18, 2013 10:35:46 AM Bjorn Helgaas wrote:
> On Fri, Jan 18, 2013 at 9:07 AM, Jiang Liu <liuj97@gmail.com> wrote:
> > If user specifies "pci=nopciehp" on kernel boot command line, OSPM
> > won't claim PCIe native hotplug service from firmware and no PCIe
> > port devices will be created for PCIe native hotplug service.
> 
> Why do we need this option?
> 
> If I understand correctly, there are machines where it *looks* like we
> should use pciehp, but pciehp doesn't work because we don't get the
> interrupts we expect.  On those machines, we have to use acpiphp
> instead.  It seems like many Dell XPS laptops have this issue with
> ExpressCard slots, e.g.,
> https://bugzilla.kernel.org/show_bug.cgi?id=40802 .
> 
> If you want "pci=nopciehp" as a way for users to deal with this
> problem by forcing the use of acpiphp, I object.  Windows manages to
> make these slots work without having users do anything special, so we
> should be able to do it, too.

And one can use pcie_ports=compat to work around these problems anyway.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.