linux-kernel - Re: [PATCH] PCI/shpchp: fix a bus speed issue on hotplug

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Date:	Thu, 01 May 2014 21:57:05 +0300
From:	Marcel Apfelbaum <marcel.apfelbaum@...il.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Matthew Wilcox <matthew@....cx>,
	"Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH] PCI/shpchp: fix a bus speed issue on hotplug

On Thu, 2014-05-01 at 21:13 +0300, Marcel Apfelbaum wrote:
> On Thu, 2014-05-01 at 12:02 -0600, Bjorn Helgaas wrote:
> > On Thu, May 1, 2014 at 8:35 AM, Marcel Apfelbaum <marcel.a@...hat.com> wrote:
> > > When a board is added, the shpchp driver checks if there
> > > is a mismatch between the bridge's adapter and the bus speed.
> > > If there is, it sets the subordinate speed (if there is no device on it).
> > >
> > > However, it takes the reference of the board speed from the primary bus
> > > and not from the subordinate. If the primary bus is PCI and not PCIX/PCIe,
> > > its speed is not updated and remains 0xff. As a result hotplug fails
> > > with error: "Speed of bus ff and adapter 0 mismatch".
> > 
> > It'd be cool to have a bugzilla for this with lspci and dmesg output.
> > I'll also have to check the other hotplug drivers for similar issues,
> > unless you've already done that.
> I'll open a BZ with the details, sure.
Done: https://bugzilla.kernel.org/show_bug.cgi?id=75251
If you need further details, please let me know.

Thanks,
Marcel


> 
> I didn't check the other hotplug drivers, but I do plan
> to look into PCIe driver as part of QEMU's PCIe hotplug feature.
> 
> Thanks,
> Marcel
> 
> > 
> > > Fixed that by checking the speed against the subordinate bus.
> > >
> > > Signed-off-by: Marcel Apfelbaum <marcel.a@...hat.com>
> > > Acked-by: Michael S. Tsirkin <mst@...hat.com>
> > > ---
> > >  drivers/pci/hotplug/shpchp_ctrl.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/pci/hotplug/shpchp_ctrl.c b/drivers/pci/hotplug/shpchp_ctrl.c
> > > index 5849927..6efc2ec 100644
> > > --- a/drivers/pci/hotplug/shpchp_ctrl.c
> > > +++ b/drivers/pci/hotplug/shpchp_ctrl.c
> > > @@ -282,8 +282,8 @@ static int board_added(struct slot *p_slot)
> > >                 return WRONG_BUS_FREQUENCY;
> > >         }
> > >
> > > -       bsp = ctrl->pci_dev->bus->cur_bus_speed;
> > > -       msp = ctrl->pci_dev->bus->max_bus_speed;
> > > +       bsp = ctrl->pci_dev->subordinate->cur_bus_speed;
> > > +       msp = ctrl->pci_dev->subordinate->max_bus_speed;
> > >
> > >         /* Check if there are other slots or devices on the same bus */
> > >         if (!list_empty(&ctrl->pci_dev->subordinate->devices))
> > > --
> > > 1.8.3.1
> > >
> 
> 
> 
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