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dmaengine: ioatdma: Ignore IOAT devices under hotplug-capable PCI host bridge

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The dmaengine core assumes that async DMA devices will only be removed
when they not used anymore, or it assumes dma_async_device_unregister()
will only be called by dma driver exit routines. But this assumption is
not true for the IOAT driver, which calls dma_async_device_unregister()
from ioat_remove(). So current IOAT driver doesn't support device
hot-removal because it may cause system crash to hot-remove an inuse
IOAT device.

To support CPU socket hot-removal, all PCI devices, including IOAT
devices embedded in the socket, will be hot-removed. The idea solution
is to enhance the dmaengine core and IOAT driver to support hot-removal,
but that's too hard.

This patch implements a hack to disable IOAT devices under hotplug-capable
CPU socket so it won't break socket hot-removal.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
This commit is contained in:
Jiang Liu 2015-07-08 15:41:42 +08:00 committed by Vinod Koul
parent 7618d0359c
commit b6c52c6345
1 changed files with 34 additions and 0 deletions
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34
drivers/dma/ioat/pci.c
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@ -27,6 +27,7 @@
#include <linux/interrupt.h>
#include <linux/dca.h>
#include <linux/slab.h>
#include <linux/acpi.h>
#include "dma.h"
#include "dma_v2.h"
#include "registers.h"
@ -148,6 +149,34 @@ alloc_ioatdma(struct pci_dev *pdev, void __iomem *iobase)
return d;
}
/*
* The dmaengine core assumes that async DMA devices will only be removed
* when they not used anymore, or it assumes dma_async_device_unregister()
* will only be called by dma driver exit routines. But this assumption is
* not true for the IOAT driver, which calls dma_async_device_unregister()
* from ioat_remove(). So current IOAT driver doesn't support device
* hot-removal because it may cause system crash to hot-remove inuse IOAT
* devices.
*
* This is a hack to disable IOAT devices under ejectable PCI host bridge
* so it won't break PCI host bridge hot-removal.
*/
static bool ioat_pci_has_ejectable_acpi_ancestor(struct pci_dev *pdev)
{
#ifdef CONFIG_ACPI
struct pci_bus *bus = pdev->bus;
struct acpi_device *adev;
while (bus->parent)
bus = bus->parent;
for (adev = ACPI_COMPANION(bus->bridge); adev; adev = adev->parent)
if (adev->flags.ejectable)
return true;
#endif
return false;
}
static int ioat_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
{
void __iomem * const *iomap;
@ -155,6 +184,11 @@ static int ioat_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
struct ioatdma_device *device;
int err;
if (ioat_pci_has_ejectable_acpi_ancestor(pdev)) {
dev_dbg(&pdev->dev, "ignore ejectable IOAT device.\n");
return -ENODEV;
}
err = pcim_enable_device(pdev);
if (err)
return err;