PCI: endpoint: Add PCI Endpoint function driver for MHI bus

Add PCI Endpoint driver for the Qualcomm MHI (Modem Host Interface) bus.

The driver implements the MHI function over PCI in the endpoint device such
as SDX55 modem. The MHI endpoint function driver acts as a controller
driver for the MHI Endpoint stack and carries out all PCI related
functionality.

Link: https://lore.kernel.org/r/20230602114756.36586-9-manivannan.sadhasivam@linaro.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kishon Vijay Abraham I <kishon@kernel.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

PCI: endpoint: Support NTB transfer between RC and EP

Add NTB function driver and virtual PCI Bus and Virtual NTB driver
to implement communication between PCIe Root Port and PCIe EP devices

┌────────────┐ ┌─────────────────────────────────────┐
│ │ │ │
├────────────┤ │ ┌──────────────┤
│ NTB │ │ │ NTB │
│ NetDev │ │ │ NetDev │
├────────────┤ │ ├──────────────┤
│ NTB │ │ │ NTB │
│ Transfer │ │ │ Transfer │
├────────────┤ │ ├──────────────┤
│ │ │ │ │
│ PCI NTB │ │ │ │
│ EPF │ │ │ │
│ Driver │ │ │ PCI Virtual │
│ │ ├───────────────┐ │ NTB Driver │
│ │ │ PCI EP NTB │◄────►│ │
│ │ │ FN Driver │ │ │
├────────────┤ ├───────────────┤ ├──────────────┤
│ │ │ │ │ │
│ PCI Bus │ ◄─────► │ PCI EP Bus │ │ Virtual PCI │
│ │ PCI │ │ │ Bus │
└────────────┘ └───────────────┴──────┴──────────────┘
PCIe Root Port PCI EP

This driver includes 3 parts:
1 PCI EP NTB function driver
2 Virtual PCI bus
3 PCI virtual NTB driver, which is loaded only by above virtual PCI bus

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

PCI: endpoint: Add EP function driver to provide NTB functionality

Add a new endpoint function driver to provide NTB functionality using
multiple PCIe endpoint instances.

[arnd@arndb.de: Select configfs dependency]
[yebin10@huawei.com: Fix unused but set variables]
[geert+renesas@glider.be: Explain NTB in PCI_EPF_NTB help text]

Link: https://lore.kernel.org/r/20210201195809.7342-14-kishon@ti.com
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ye Bin <yebin10@huawei.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

PCI: Add SPDX GPL-2.0 when no license was specified

b24413180f56 ("License cleanup: add SPDX GPL-2.0 license identifier to
files with no license") added SPDX GPL-2.0 to several PCI files that
previously contained no license information.

Add SPDX GPL-2.0 to all other PCI files that did not contain any license
information and hence were under the default GPL version 2 license of the
kernel.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

PCI: endpoint: functions: Add an EP function to test PCI

Adds a new endpoint function driver (to program the virtual test device)
making use of the EP-core library.

[bhelgaas: fold in pci_epf_test_probe() -ENOMEM test from Wei Yongjun
<weiyongjun1@huawei.com>]
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>