linux-kernel - [PATCH 4.19 214/267] PCI: Add NVIDIA GPU multi-function power dependencies

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Message-Id: <20200619141658.994953070@linuxfoundation.org>
Date:   Fri, 19 Jun 2020 16:33:19 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Abhishek Sahu <abhsahu@...dia.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 214/267] PCI: Add NVIDIA GPU multi-function power dependencies

From: Abhishek Sahu <abhsahu@...dia.com>

[ Upstream commit 6d2e369f0d4c3e6125c886847c04106b03d2609e ]

The NVIDIA Turing GPU is a multi-function PCI device with the following
functions:

  - Function 0: VGA display controller
  - Function 1: Audio controller
  - Function 2: USB xHCI Host controller
  - Function 3: USB Type-C UCSI controller

Function 0 is tightly coupled with other functions in the hardware.  When
function 0 is in D3, it gates power for hardware blocks used by other
functions, which means those functions only work when function 0 is in D0.
If any of these functions (1/2/3) are in D0, then function 0 should also be
in D0.

Commit 07f4f97d7b4b ("vga_switcheroo: Use device link for HDA controller")
already creates a device link to show the dependency of function 1 on
function 0 of this GPU.  Create additional device links to express the
dependencies of functions 2 and 3 on function 0.  This means function 0
will be in D0 if any other function is in D0.

[bhelgaas: I think the PCI spec expectation is that functions can be
power-managed independently, so I don't think this device is technically
compliant.  For example, the PCIe r5.0 spec, sec 1.4, says "the PCI/PCIe
hardware/software model includes architectural constructs necessary to
discover, configure, and use a Function, without needing Function-specific
knowledge" and sec 5.1 says "D states are associated with a particular
Function" and "PM provides ... a mechanism to identify power management
capabilities of a given Function [and] the ability to transition a Function
into a certain power management state."]

Link: https://lore.kernel.org/lkml/20190606092225.17960-3-abhsahu@nvidia.com
Signed-off-by: Abhishek Sahu <abhsahu@...dia.com>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/pci/quirks.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index d6236bb26950..8ac2d5a4a224 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -5094,6 +5094,32 @@ DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_AMD, PCI_ANY_ID,
 DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
 			      PCI_CLASS_MULTIMEDIA_HD_AUDIO, 8, quirk_gpu_hda);

+/*
+ * Create device link for NVIDIA GPU with integrated USB xHCI Host
+ * controller to VGA.
+ */
+static void quirk_gpu_usb(struct pci_dev *usb)
+{
+	pci_create_device_link(usb, 2, 0, PCI_BASE_CLASS_DISPLAY, 16);
+}
+DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
+			      PCI_CLASS_SERIAL_USB, 8, quirk_gpu_usb);
+
+/*
+ * Create device link for NVIDIA GPU with integrated Type-C UCSI controller
+ * to VGA. Currently there is no class code defined for UCSI device over PCI
+ * so using UNKNOWN class for now and it will be updated when UCSI
+ * over PCI gets a class code.
+ */
+#define PCI_CLASS_SERIAL_UNKNOWN	0x0c80
+static void quirk_gpu_usb_typec_ucsi(struct pci_dev *ucsi)
+{
+	pci_create_device_link(ucsi, 3, 0, PCI_BASE_CLASS_DISPLAY, 16);
+}
+DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
+			      PCI_CLASS_SERIAL_UNKNOWN, 8,
+			      quirk_gpu_usb_typec_ucsi);
+
 /*
  * Some IDT switches incorrectly flag an ACS Source Validation error on
  * completions for config read requests even though PCIe r4.0, sec
-- 
2.25.1