linux-kernel - [PATCH] PCI: pciehp: Flush slot control prior to reset

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Message-ID: <20141107225359.1937.61243.stgit@gimli.home>
Date:	Fri, 07 Nov 2014 15:54:41 -0700
From:	Alex Williamson <alex.williamson@...hat.com>
To:	linux-pci@...r.kernel.org, bhelgaas@...gle.com
Cc:	linux-kernel@...r.kernel.org, rajatxjain@...il.com,
	yinghai@...nel.org
Subject: [PATCH] PCI: pciehp: Flush slot control prior to reset

Since 3461a068661c we don't automatically do a pcie_wait_cmd() for
as part of pcie_write_cmd(), it needs to be called explicitly or
triggered by the next pcie_write_cmd().  However, when we do a
secondary bus reset and we're using pcie_write_cmd() to make sure
that we don't see that bus reset as a hotplug event, we really want
to make sure the update is complete.  Testing on an old Lenovo S20
system, which sets surprise hotplug for some slots, this failure to
flush results in a link down event seen by the hotplug controller
when we issue the bus reset and returns us to the undesireable
behavior of removing and re-adding the device.  Force a flush by
adding an explicit call to pcie_wait_cmd().

Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
Cc: stable@...r.kernel.org [3.17]
---

 drivers/pci/hotplug/pciehp_hpc.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 0ebf754..e540966 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -660,6 +660,7 @@ int pciehp_reset_slot(struct slot *slot, int probe)
 		 pci_pcie_cap(ctrl->pcie->port) + PCI_EXP_SLTCTL, 0);
 	if (pciehp_poll_mode)
 		del_timer_sync(&ctrl->poll_timer);
+	pcie_wait_cmd(ctrl);

 	pci_reset_bridge_secondary_bus(ctrl->pcie->port);

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