Add support for the endpoint mode of Synopsys DesignWare core based
dual mode PCIe controllers present in Tegra194 SoC.

Signed-off-by: Vidya Sagar <redacted>
---
V4:
* Addressed Lorenzo's review comments
* Started using threaded irqs instead of kthreads

V3:
* Addressed Thierry's review comments

V2:
* Addressed Bjorn's review comments
* Made changes as part of addressing review comments for other patches

 drivers/pci/controller/dwc/Kconfig         |  30 +-
 drivers/pci/controller/dwc/pcie-tegra194.c | 681 ++++++++++++++++++++-
 2 files changed, 693 insertions(+), 18 deletions(-)

diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
index 0830dfcfa43a..169cde58dd92 100644
--- a/drivers/pci/controller/dwc/Kconfig
+++ b/drivers/pci/controller/dwc/Kconfig

@@ -248,14 +248,38 @@ config PCI_MESON
 	  implement the driver.
 
 config PCIE_TEGRA194
-	tristate "NVIDIA Tegra194 (and later) PCIe controller"
+	tristate
+
+config PCIE_TEGRA194_HOST
+	tristate "NVIDIA Tegra194 (and later) PCIe controller - Host Mode"
 	depends on ARCH_TEGRA_194_SOC || COMPILE_TEST
 	depends on PCI_MSI_IRQ_DOMAIN
 	select PCIE_DW_HOST
 	select PHY_TEGRA194_P2U
+	select PCIE_TEGRA194
+	default y
+	help
+	  Enables support for the PCIe controller in the NVIDIA Tegra194 SoC to
+	  work in host mode. There are two instances of PCIe controllers in
+	  Tegra194. This controller can work either as EP or RC. In order to
+	  enable host-specific features PCIE_TEGRA194_HOST must be selected and
+	  in order to enable device-specific features PCIE_TEGRA194_EP must be
+	  selected. This uses the DesignWare core.
+
+config PCIE_TEGRA194_EP
+	tristate "NVIDIA Tegra194 (and later) PCIe controller - Endpoint Mode"
+	depends on ARCH_TEGRA_194_SOC || COMPILE_TEST
+	depends on PCI_ENDPOINT
+	select PCIE_DW_EP
+	select PHY_TEGRA194_P2U
+	select PCIE_TEGRA194
 	help
-	  Say Y here if you want support for DesignWare core based PCIe host
-	  controller found in NVIDIA Tegra194 SoC.
+	  Enables support for the PCIe controller in the NVIDIA Tegra194 SoC to
+	  work in host mode. There are two instances of PCIe controllers in
+	  Tegra194. This controller can work either as EP or RC. In order to
+	  enable host-specific features PCIE_TEGRA194_HOST must be selected and
+	  in order to enable device-specific features PCIE_TEGRA194_EP must be
+	  selected. This uses the DesignWare core.
 
 config PCIE_UNIPHIER
 	bool "Socionext UniPhier PCIe controllers"

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index cbe95f0ea0ca..81810e644b23 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c

@@ -14,6 +14,8 @@
 #include <linux/interrupt.h>
 #include <linux/iopoll.h>
 #include <linux/kernel.h>
+#include <linux/kfifo.h>
+#include <linux/kthread.h>