linux-kernel - Re: [PATCH 3/3] PCI Hotplug: workaround for Thunderbolt on Intel DZ77RE-75K motherboard

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Date:	Thu, 13 Dec 2012 22:08:57 +0200
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Miles J Penner <miles.j.penner@...el.com>,
	John Ronciak <john.ronciak@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Tushar N Dave <tushar.n.dave@...el.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Amos Kong <kongjianjun@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] PCI Hotplug: workaround for Thunderbolt on Intel
 DZ77RE-75K motherboard

On Thu, Dec 13, 2012 at 10:48:20AM -0800, Greg KH wrote:
> On Thu, Dec 13, 2012 at 05:31:48PM +0200, Kirill A. Shutemov wrote:
> > From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> > 
> > BIOS on Intel DZ77RE-75K motherboard notifies OS about Thunderbolt
> > hotplug before devices behind Thunderbolt are ready to be enumerated.
> > 
> > Let's delay enumeration by 2 seconds.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > ---
> >  drivers/pci/hotplug/acpiphp_glue.c |   16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> > index 1a2b3ca..165987a 100644
> > --- a/drivers/pci/hotplug/acpiphp_glue.c
> > +++ b/drivers/pci/hotplug/acpiphp_glue.c
> > @@ -49,6 +49,7 @@
> >  #include <linux/mutex.h>
> >  #include <linux/slab.h>
> >  #include <linux/acpi.h>
> > +#include <linux/dmi.h>
> >  
> >  #include "../pci.h"
> >  #include "acpiphp.h"
> > @@ -1327,6 +1328,19 @@ out:
> >  static void handle_hotplug_event_bridge(acpi_handle handle, u32 type,
> >  					void *context)
> >  {
> > +	unsigned long delay = 0;
> > +	const char *board_name;
> > +
> > +	board_name = dmi_get_system_info(DMI_BOARD_NAME);
> > +	/*
> > +	 * BIOS on Intel DZ77RE-75K motherboard notifies OS about Thunderbolt
> > +	 * hotplug before devices behind Thunderbolt are ready to be
> > +	 * enumerated.
> > +	 * Let's delay enumeration by 2 seconds.
> > +	 */
> > +	if (board_name && !strcmp(board_name, "DZ77RE-75K"))
> > +		delay = 2 * HZ;
> 
> Again, no objection to this patch as-is, but should we make it a bit
> more "general" and provide a quirk table to make this type of fix easier
> for other motherboards?  Shouldn't we also match on a manufacturer field
> as well as the board_name?  The kernel provides a very easy to match on
> any arbritary set of DMI fields for this kind of problem that we could
> use here.

Something like this (untested):

diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index 1a2b3ca..c4db634 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -49,6 +49,7 @@
 #include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/acpi.h>
+#include <linux/dmi.h>
 
 #include "../pci.h"
 #include "acpiphp.h"
@@ -1327,6 +1328,31 @@ out:
 static void handle_hotplug_event_bridge(acpi_handle handle, u32 type,
 					void *context)
 {
+	unsigned long delay = 0;
+	const struct dmi_system_id *match;
+	static const struct dmi_system_id sysids[] = {
+		/*
+		 * BIOS on Intel DZ77RE-75K motherboard notifies OS about
+		 * Thunderbolt hotplug before devices behind Thunderbolt are
+		 * ready to be enumerated.
+		 * Let's delay enumeration by 2 seconds.
+		 */
+		{
+			.ident = "DZ77RE-75K",
+			.matches = {
+				DMI_MATCH(DMI_BOARD_VENDOR,
+						"Intel Corporation"),
+				DMI_MATCH(DMI_BOARD_NAME,
+						"DZ77RE-75K"),
+			},
+			.driver_data = (void *) (2 * HZ), /* delay */
+		},
+	};
+
+	match = dmi_first_match(sysids);
+	if (match)
+		delay = (unsigned long) match->driver_data;
+
 	/*
 	 * Currently the code adds all hotplug events to the kacpid_wq
 	 * queue when it should add hotplug events to the kacpi_hotplug_wq.
@@ -1336,7 +1362,7 @@ static void handle_hotplug_event_bridge(acpi_handle handle, u32 type,
 	 * don't deadlock on hotplug actions.
 	 */
 	alloc_acpiphp_hp_work(handle, type, context,
-			      _handle_hotplug_event_bridge, 0);
+			      _handle_hotplug_event_bridge, delay);
 }
 
 static void _handle_hotplug_event_func(struct work_struct *work)

-- 
 Kirill A. Shutemov

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