From b6c52c634506d52b3a2dc18503980d717e478739 Mon Sep 17 00:00:00 2001 From: Jiang Liu Date: Wed, 8 Jul 2015 15:41:42 +0800 Subject: dmaengine: ioatdma: Ignore IOAT devices under hotplug-capable PCI host bridge 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 Signed-off-by: Vinod Koul --- drivers/dma/ioat/pci.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/drivers/dma/ioat/pci.c b/drivers/dma/ioat/pci.c index 76f0dc6..3b8c9b0 100644 --- a/drivers/dma/ioat/pci.c +++ b/drivers/dma/ioat/pci.c @@ -27,6 +27,7 @@ #include #include #include +#include #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; -- cgit v1.1