linux-kernel - [PATCH 1/2] PCI: Code reorganization for VGA device link

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Date:   Fri, 31 May 2019 10:31:08 +0530
From:   Abhishek Sahu <abhsahu@...dia.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Abhishek Sahu <abhsahu@...dia.com>
Subject: [PATCH 1/2] PCI: Code reorganization for VGA device link

This patch does minor code reorganization. It introduces a helper
function which creates device link from the non-VGA controller
(consumer) to the VGA (supplier) and uses this helper function for
creating device link from integrated HDA controller to VGA. It will
help in subsequent patches which require a similar kind of device
link from USB/Type-C USCI controller to VGA.

Signed-off-by: Abhishek Sahu <abhsahu@...dia.com>
---
 drivers/pci/quirks.c | 44 +++++++++++++++++++++++++++++---------------
 1 file changed, 29 insertions(+), 15 deletions(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index a077f67fe1da..a20f7771a323 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -4916,36 +4916,50 @@ 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.
+ * GPUs can be multi-function PCI device which can contain controllers other
+ * than VGA (like Audio, USB, etc.). Internally in the hardware, these non-VGA
+ * controllers are tightly coupled with VGA controller. Whenever these
+ * controllers are runtime active, the VGA controller should also be in active
+ * state. Normally, in these GPUs, the VGA controller is present at function 0.
+ *
+ * This is a helper function which creates device link from the non-VGA
+ * controller (consumer) to the VGA (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 these non-VGA controllers to prevent
+ * it from permanently keeping the GPU awake.
  */
-static void quirk_gpu_hda(struct pci_dev *hda)
+static void
+pci_create_device_link_with_vga(struct pci_dev *pdev, unsigned int devfn)
 {
 	struct pci_dev *gpu;
 
-	if (PCI_FUNC(hda->devfn) != 1)
+	if (PCI_FUNC(pdev->devfn) != devfn)
 		return;
 
-	gpu = pci_get_domain_bus_and_slot(pci_domain_nr(hda->bus),
-					  hda->bus->number,
-					  PCI_DEVFN(PCI_SLOT(hda->devfn), 0));
+	gpu = pci_get_domain_bus_and_slot(pci_domain_nr(pdev->bus),
+					  pdev->bus->number,
+					  PCI_DEVFN(PCI_SLOT(pdev->devfn), 0));
 	if (!gpu || (gpu->class >> 16) != PCI_BASE_CLASS_DISPLAY) {
 		pci_dev_put(gpu);
 		return;
 	}
 
-	if (!device_link_add(&hda->dev, &gpu->dev,
+	if (!device_link_add(&pdev->dev, &gpu->dev,
 			     DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME))
-		pci_err(hda, "cannot link HDA to GPU %s\n", pci_name(gpu));
+		pci_err(pdev, "cannot link with VGA %s\n", pci_name(gpu));
 
-	pm_runtime_allow(&hda->dev);
+	pm_runtime_allow(&pdev->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_with_vga(hda, 1);
+}
 DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_ATI, PCI_ANY_ID,
 			      PCI_CLASS_MULTIMEDIA_HD_AUDIO, 8, quirk_gpu_hda);
 DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_AMD, PCI_ANY_ID,
-- 
2.17.1