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    SubjectRe: [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@linux.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@linux.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
    [unhandled content-type:application/pgp-signature]
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