[PATCH 4.19 227/267] PCI: Generalize multi-function power dependency device links

Greg Kroah-Hartman
2020-06-19T15:03:22Z

From: Abhishek Sahu <abhsahu@nvidia.com>

[ Upstream commit a17beb1a0882a544523dcb5d0da4801272dfd43a ]

Although not allowed by the PCI specs, some multi-function devices have
power dependencies between the functions. For example, function 1 may not
work unless function 0 is in the D0 power state.

The existing quirk_gpu_hda() adds a device link to express this dependency
for GPU and HDA devices, but it really is not specific to those device
types.

Generalize it and rename it to pci_create_device_link() so we can create
dependencies between any "consumer" and "producer" functions of a
multi-function device, where the consumer is only functional if the
producer is in D0. This reorganization should not affect any
functionality.

Link: https://lore.kernel.org/lkml/20190606092225.17960-2-abhsahu@nvidia.com
Signed-off-by: Abhishek Sahu <abhsahu@nvidia.com>
[bhelgaas: commit log, reword diagnostic]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pci/quirks.c | 54 ++++++++++++++++++++++++++++----------------
1 file changed, 34 insertions(+), 20 deletions(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 0704025a2160..0862cb633849 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -5077,35 +5077,49 @@ static void quirk_fsl_no_msi(struct pci_dev *pdev)
DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_FREESCALE, PCI_ANY_ID, quirk_fsl_no_msi);

/*
- * GPUs with integrated HDA controller for streaming audio to attached displays
- * need a device link from the HDA controller (consumer) to the GPU (supplier)
- * so that the GPU is powered up whenever the HDA controller is accessed.
- * The GPU and HDA controller are functions 0 and 1 of the same PCI device.
- * The device link stays in place until shutdown (or removal of the PCI device
- * if it's hotplugged). Runtime PM is allowed by default on the HDA controller
- * to prevent it from permanently keeping the GPU awake.
+ * Although not allowed by the spec, some multi-function devices have
+ * dependencies of one function (consumer) on another (supplier). For the
+ * consumer to work in D0, the supplier must also be in D0. Create a
+ * device link from the consumer to the supplier to enforce this
+ * dependency. Runtime PM is allowed by default on the consumer to prevent
+ * it from permanently keeping the supplier awake.
*/
-static void quirk_gpu_hda(struct pci_dev *hda)
+static void pci_create_device_link(struct pci_dev *pdev, unsigned int consumer,
+ unsigned int supplier, unsigned int class,
+ unsigned int class_shift)
{
- struct pci_dev *gpu;
+ struct pci_dev *supplier_pdev;

- if (PCI_FUNC(hda->devfn) != 1)
+ if (PCI_FUNC(pdev->devfn) != consumer)
return;

- gpu = pci_get_domain_bus_and_slot(pci_domain_nr(hda->bus),
- hda->bus->number,
- PCI_DEVFN(PCI_SLOT(hda->devfn), 0));
- if (!gpu || (gpu->class >> 16) != PCI_BASE_CLASS_DISPLAY) {
- pci_dev_put(gpu);
+ supplier_pdev = pci_get_domain_bus_and_slot(pci_domain_nr(pdev->bus),
+ pdev->bus->number,
+ PCI_DEVFN(PCI_SLOT(pdev->devfn), supplier));
+ if (!supplier_pdev || (supplier_pdev->class >> class_shift) != class) {
+ pci_dev_put(supplier_pdev);
return;
}

- if (!device_link_add(&hda->dev, &gpu->dev,
- DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME))
- pci_err(hda, "cannot link HDA to GPU %s\n", pci_name(gpu));
+ if (device_link_add(&pdev->dev, &supplier_pdev->dev,
+ DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME))
+ pci_info(pdev, "D0 power state depends on %s\n",
+ pci_name(supplier_pdev));
+ else
+ pci_err(pdev, "Cannot enforce power dependency on %s\n",
+ pci_name(supplier_pdev));
+
+ pm_runtime_allow(&pdev->dev);
+ pci_dev_put(supplier_pdev);
+}

- pm_runtime_allow(&hda->dev);
- pci_dev_put(gpu);
+/*
+ * Create device link for GPUs with integrated HDA controller for streaming
+ * audio to attached displays.
+ */
+static void quirk_gpu_hda(struct pci_dev *hda)
+{
+ pci_create_device_link(hda, 1, 0, PCI_BASE_CLASS_DISPLAY, 16);
}
DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_ATI, PCI_ANY_ID,
PCI_CLASS_MULTIMEDIA_HD_AUDIO, 8, quirk_gpu_hda);
--
2.25.1