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From:   Abhishek Sahu <abhsahu@nvidia.com>
To:     Bjorn Helgaas <bhelgaas@google.com>
CC:     <linux-pci@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <lukas@wunner.de>, Abhishek Sahu <abhsahu@nvidia.com>
Subject: [PATCH v2 1/2] PCI: Code reorganization for creating device link
Date:   Thu, 6 Jun 2019 14:52:24 +0530
Message-ID: <20190606092225.17960-2-abhsahu@nvidia.com>
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In Multi-function PCI device, one function (consumer) can have
hardware functional dependencies on another function (supplier).
Whenever the consumer is active and in D0 state, the supplier should
also be in D0 state. Currently, the device link is being created from
HDA function to VGA function for GPU's. This patch does minor code
reorganization. It introduces a helper function which creates device
link from consumer pci device to supplier pci device and uses this
helper function for creating device link from HDA to VGA. This helper
function can be used in future for creating device link from one
function to another function.

Signed-off-by: Abhishek Sahu <abhsahu@nvidia.com>
---
* Changes from v1:

  1. Make the helper function generic which takes supplier class,
     class shift and function number also.
  2. Minor changes in commit log

 drivers/pci/quirks.c | 53 +++++++++++++++++++++++++++-----------------
 1 file changed, 33 insertions(+), 20 deletions(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index a077f67fe1da..379cd7fbcb12 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -4916,35 +4916,48 @@ 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.
+ * Multi-function PCI devices can have hardware functional dependencies from
+ * one function (consumer) to another function (supplier). Whenever the
+ * consumer is in D0 state, the supplier should also be in D0 state. This is
+ * a helper function which creates device link from the consumer to the
+ * supplier.  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
+ * consumers 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, "Linked with %s\n", pci_name(supplier_pdev));
+	else
+		pci_err(pdev, "Cannot link with %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);
-- 
2.17.1