PCI: qcom-ep: Add Qualcomm PCIe Endpoint controller driver

Add driver for Qualcomm PCIe Endpoint controller based on the DesignWare
core with added Qualcomm-specific wrapper around the core. The driver
support is very basic such that it supports only enumeration, PCIe
read/write, and MSI. There is no ASPM and PM support for now but these will
be added later.

The driver is capable of using the PERST# and WAKE# side-band GPIOs for
operation and written on top of the DWC PCI framework.

[bhelgaas: wrap a few long lines]
Co-developed-by: Siddartha Mohanadoss <smohanad@codeaurora.org>
[mani: restructured the driver and fixed several bugs for upstream]
Link: https://lore.kernel.org/r/20210920065946.15090-3-manivannan.sadhasivam@linaro.org
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rob Herring <robh@kernel.org>

Author: Mani-Sadhasivam

drivers/pci/controller/dwc/Kconfig

@@ -180,6 +180,16 @@ config PCIE_QCOM
 	  PCIe controller uses the DesignWare core plus Qualcomm-specific
 	  hardware wrappers.
 
+config PCIE_QCOM_EP
+	tristate "Qualcomm PCIe controller - Endpoint mode"
+	depends on OF && (ARCH_QCOM || COMPILE_TEST)
+	depends on PCI_ENDPOINT
+	select PCIE_DW_EP
+	help
+	  Say Y here to enable support for the PCIe controllers on Qualcomm SoCs
+	  to work in endpoint mode. The PCIe controller uses the DesignWare core
+	  plus Qualcomm-specific hardware wrappers.
+
 config PCIE_ARMADA_8K
 	bool "Marvell Armada-8K PCIe controller"
 	depends on ARCH_MVEBU || COMPILE_TEST

drivers/pci/controller/dwc/Makefile

@@ -12,6 +12,7 @@ obj-$(CONFIG_PCI_KEYSTONE) += pci-keystone.o
 obj-$(CONFIG_PCI_LAYERSCAPE) += pci-layerscape.o
 obj-$(CONFIG_PCI_LAYERSCAPE_EP) += pci-layerscape-ep.o
 obj-$(CONFIG_PCIE_QCOM) += pcie-qcom.o
+obj-$(CONFIG_PCIE_QCOM_EP) += pcie-qcom-ep.o
 obj-$(CONFIG_PCIE_ARMADA_8K) += pcie-armada8k.o
 obj-$(CONFIG_PCIE_ARTPEC6) += pcie-artpec6.o
 obj-$(CONFIG_PCIE_ROCKCHIP_DW_HOST) += pcie-dw-rockchip.o

drivers/pci/controller/dwc/pcie-designware-ep.c

@@ -83,6 +83,7 @@ void dw_pcie_ep_reset_bar(struct dw_pcie *pci, enum pci_barno bar)
 	for (func_no = 0; func_no < funcs; func_no++)
 		__dw_pcie_ep_reset_bar(pci, func_no, bar, 0);
 }
+EXPORT_SYMBOL_GPL(dw_pcie_ep_reset_bar);
 
 static u8 __dw_pcie_ep_find_next_cap(struct dw_pcie_ep *ep, u8 func_no,
 		u8 cap_ptr, u8 cap)
@@ -485,6 +486,7 @@ int dw_pcie_ep_raise_legacy_irq(struct dw_pcie_ep *ep, u8 func_no)
 
 	return -EINVAL;
 }
+EXPORT_SYMBOL_GPL(dw_pcie_ep_raise_legacy_irq);
 
 int dw_pcie_ep_raise_msi_irq(struct dw_pcie_ep *ep, u8 func_no,
 			     u8 interrupt_num)
@@ -536,6 +538,7 @@ int dw_pcie_ep_raise_msi_irq(struct dw_pcie_ep *ep, u8 func_no,
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(dw_pcie_ep_raise_msi_irq);
 
 int dw_pcie_ep_raise_msix_irq_doorbell(struct dw_pcie_ep *ep, u8 func_no,
 				       u16 interrupt_num)