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

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Date:	Mon, 18 May 2015 02:26:42 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Jarod Wilson <jarod@...hat.com>, linux-kernel@...r.kernel.org,
	Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci/hotplug: work-around for missing _RMV on HP ZBook G2

On Saturday, May 16, 2015 09:41:55 AM Bjorn Helgaas wrote:
> [fix Rafael's email address]

Thanks. :-)

> 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?

In theory, that should depend on the _OSC handshake in acpi_pci_root_add().

If the firmware doesn't give us control of the PCIe features, we'll not use
pciehp (or at least that's the idea).

acpiphp is used if pciehp doesn't claim the device, AFAICS.

Rafael

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