linux-kernel - Re: [PATCH] pci/hotplug: work-around for missing

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Message-ID: <20150516144155.GH31666@google.com>
Date:	Sat, 16 May 2015 09:41:55 -0500
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Jarod Wilson <jarod@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Len Brown <lenb@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci/hotplug: work-around for missing _RMV on HP ZBook G2

[fix Rafael's email address]

On Sat, May 16, 2015 at 09:37:50AM -0500, Bjorn Helgaas wrote:
> Hi Jarod,
> 
> On Thu, May 14, 2015 at 03:33:58PM -0400, Jarod Wilson wrote:
> > The HP ZBook 15 and 17 Mobile Workstations, generation 2, up to and
> > including at least BIOS revision 01.07, do not have an ACPI _RMV object
> > associated with their expresscard slots, so acpi-based hotplug-capable
> > slot detection fails. If we fall back to pcie-based detection, the systems
> > work just fine, so this uses dmi matching to do that. With luck, a future
> > BIOS will remedy this (I've let someone at HP know about the problem),
> > but for now, just use this for all existing versions.
> > 
> > Note: they *do* have a proper _RMV object for what I believe is their
> > thunderbolt ports.
> > 
> > Tested successfully on an HP ZBook 17 G2 and HP ZBook 15 G2.
> > 
> > CC: Len Brown <lenb@...nel.org>
> > CC: "Rafael J. Wysocki" <rjw@...k.pl>
> > CC: Bjorn Helgaas <bhelgaas@...gle.com>
> > CC: linux-acpi@...r.kernel.org
> > CC: linux-pci@...r.kernel.org
> > Signed-off-by: Jarod Wilson <jarod@...hat.com>
> > ---
> >  drivers/pci/hotplug/pciehp_acpi.c | 33 +++++++++++++++++++++++++++++++++
> >  1 file changed, 33 insertions(+)
> > 
> > diff --git a/drivers/pci/hotplug/pciehp_acpi.c b/drivers/pci/hotplug/pciehp_acpi.c
> > index 93cc926..db38fb5 100644
> > --- a/drivers/pci/hotplug/pciehp_acpi.c
> > +++ b/drivers/pci/hotplug/pciehp_acpi.c
> > @@ -28,6 +28,7 @@
> >  #include <linux/pci_hotplug.h>
> >  #include <linux/slab.h>
> >  #include <linux/module.h>
> > +#include <linux/dmi.h>
> >  #include "pciehp.h"
> >  
> >  #define PCIEHP_DETECT_PCIE	(0)
> > @@ -109,10 +110,40 @@ static struct pcie_port_service_driver __initdata dummy_driver = {
> >  	.probe		= dummy_probe,
> >  };
> >  
> > +static int __init set_slot_detection_mode_pcie(const struct dmi_system_id *d)
> > +{
> > +	info("%s lacks ACPI _RMV object for expresscard\n", d->ident);
> > +	return 1;
> > +}
> > +
> > +static struct dmi_system_id __initdata missing_acpi_rmv[] = {
> > +	/* ZBook 17 through at least bios v01.07 */
> > +	{
> > +	 .callback = set_slot_detection_mode_pcie,
> > +	 .ident = "HP ZBook 17 G2 Mobile Workstation",
> > +	 .matches = {
> > +		DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
> > +		DMI_MATCH(DMI_PRODUCT_NAME, "HP ZBook 17 G2"),
> > +		},
> > +	},
> > +	/* ZBook 15 through at least bios v01.07 */
> > +	{
> > +	 .callback = set_slot_detection_mode_pcie,
> > +	 .ident = "HP ZBook 15 G2 Mobile Workstation",
> > +	 .matches = {
> > +		DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
> > +		DMI_MATCH(DMI_PRODUCT_NAME, "HP ZBook 15 G2"),
> > +		},
> > +	},
> > +	{ .ident = NULL }
> > +};
> > +
> >  static int __init select_detection_mode(void)
> >  {
> >  	struct dummy_slot *slot, *tmp;
> >  
> > +	if (dmi_check_system(missing_acpi_rmv))
> > +		return PCIEHP_DETECT_PCIE;
> 
> Oh, my goodness.  I forgot how terrible this path is.  Can anyone write a
> simple explanation of how we choose to use acpiphp or pciehp?  Module
> parameters?  A dummy driver that looks for duplicate slot numbers?  Looking
> for _ADR, _EJ0, _RMV?  This is just nuts.
> 
> I can't really believe that we're doing this correctly.
> 
> If I understand correctly, the ZBooks don't have _RMV, but we try to use
> acpiphp anyway, and acpiphp doesn't work?  That sounds more like a problem
> with our acpiphp/pciehp selection "algorithm" than a BIOS bug.
> 
> Jarod, can you open a report at http://bugzilla.kernel.org and attach a
> complete dmesg log, "lspci -vv" output, and an acpidump?  I'm particularly
> interested in whether the BIOS granted us control over PCIe native hotplug.
> If it did, I wonder why we would even attempt to use acpiphp.
> 
> Bjorn
> 
> >  	if (pcie_port_service_register(&dummy_driver))
> >  		return PCIEHP_DETECT_ACPI;
> >  	pcie_port_service_unregister(&dummy_driver);
> > @@ -134,4 +165,6 @@ void __init pciehp_acpi_slot_detection_init(void)
> >  out:
> >  	if (slot_detection_mode == PCIEHP_DETECT_ACPI)
> >  		info("Using ACPI for slot detection.\n");
> > +	else if (slot_detection_mode == PCIEHP_DETECT_PCIE)
> > +		info("Using PCIE-based slot detection.\n");
> >  }
> > -- 
> > 1.8.3.1
> > 
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