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imx6: fix legacy IRQ support (4.19)

The PCIe DWC host controller is now using MSI
(Message-signaled-interrupts) by default.

While ath9k itself does support MSI here, a lot of wlan adapters do not.
Avoid non-functioning cards by simply continue to disable MSI for now.

This can be done by appending "pci=nomsi" to the boot cmdline.

Also an extra fix needs to be backported which avoids MSI initialization
which prevented legacy IRQ's init from taking over.

Signed-off-by: Koen Vandeputte <>
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xback committed Mar 21, 2019
1 parent f7a0578 commit 9c63141025ed5554891a1e4ae9be221f64ec0888
@@ -0,0 +1,48 @@
From 26a3cdb73644090ff9a2fb68775ef61d361a8883 Mon Sep 17 00:00:00 2001
From: Lucas Stach <>
Date: Wed, 27 Feb 2019 17:52:19 +0100
Subject: [PATCH] PCI: dwc: skip MSI init if MSIs have been explicitly disabled

commit 3afc8299f39a27b60e1519a28e18878ce878e7dd upstream.

Since 7c5925afbc58 (PCI: dwc: Move MSI IRQs allocation to IRQ domains
hierarchical API) the MSI init claims one of the controller IRQs as a
chained IRQ line for the MSI controller. On some designs, like the i.MX6,
this line is shared with a PCIe legacy IRQ. When the line is claimed for
the MSI domain, any device trying to use this legacy IRQs will fail to
request this IRQ line.

As MSI and legacy IRQs are already mutually exclusive on the DWC core,
as the core won't forward any legacy IRQs once any MSI has been enabled,
users wishing to use legacy IRQs already need to explictly disable MSI
support (usually via the pci=nomsi kernel commandline option). To avoid
any issues with MSI conflicting with legacy IRQs, just skip all of the
DWC MSI initalization, including the IRQ line claim, when MSI is disabled.

Fixes: 7c5925afbc58 ("PCI: dwc: Move MSI IRQs allocation to IRQ domains hierarchical API")
Tested-by: Tim Harvey <>
Signed-off-by: Lucas Stach <>
Signed-off-by: Lorenzo Pieralisi <>
Acked-by: Gustavo Pimentel <>
Signed-off-by: Greg Kroah-Hartman <>
drivers/pci/controller/dwc/pcie-designware-host.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 0fa9e8fdce66..b56e22262a77 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -439,7 +439,7 @@ int dw_pcie_host_init(struct pcie_port *pp)
if (ret)
pci->num_viewport = 2;

+ if (IS_ENABLED(CONFIG_PCI_MSI) && pci_msi_enabled()) {
* If a specific SoC driver needs to change the
* default number of vectors, it needs to implement

@@ -65,6 +65,8 @@ CONFIG_CLKSRC_IMX_GPT=y

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