PCI: xgene: Add APM X-Gene v1 PCIe MSI/MSIX termination driver

APM X-Gene v1 SoC supports its own implementation of MSI, which is not
compliant to GIC V2M specification for MSI Termination.

There is a single MSI block in X-Gene v1 SOC which serves all 5 PCIe ports.
This MSI block supports 2048 MSI termination ports coalesced into 16
physical HW IRQ lines and shared across all 5 PCIe ports.

As there are only 16 HW IRQs to serve 2048 MSI vectors, to support
set_affinity correctly for each MSI vectors, the 16 HW IRQs are statically
allocated to 8 X-Gene v1 cores (2 HW IRQs for each cores).  To steer MSI
interrupt to target CPU, MSI vector is moved around these HW IRQs lines.
With this approach, the total MSI vectors this driver supports is reduced
to 256.

[bhelgaas: squash doc, driver, maintainer update]
Signed-off-by: Duc Dang <dhdang@apm.com>
Signed-off-by: Tanmay Inamdar <tinamdar@apm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/pci/host/Kconfig b/drivers/pci/host/Kconfig
index 1dfb567b3522..9c48e9986bc7 100644
--- a/drivers/pci/host/Kconfig
+++ b/drivers/pci/host/Kconfig
@@ -89,11 +89,20 @@ config PCI_XGENE
 	depends on ARCH_XGENE
 	depends on OF
 	select PCIEPORTBUS
+	select PCI_MSI_IRQ_DOMAIN if PCI_MSI
 	help
 	  Say Y here if you want internal PCI support on APM X-Gene SoC.
 	  There are 5 internal PCIe ports available. Each port is GEN3 capable
 	  and have varied lanes from x1 to x8.
 
+config PCI_XGENE_MSI
+	bool "X-Gene v1 PCIe MSI feature"
+	depends on PCI_XGENE && PCI_MSI
+	default y
+	help
+	  Say Y here if you want PCIe MSI support for the APM X-Gene v1 SoC.
+	  This MSI driver supports 5 PCIe ports on the APM X-Gene v1 SoC.
+
 config PCI_LAYERSCAPE
 	bool "Freescale Layerscape PCIe controller"
 	depends on OF && ARM