[BACKPORT 4.14.y 2/8] PCI: designware-ep: dw_pcie_ep_set_msi() should only set MMC bits

[Arnd Bergmann]

From: Niklas Cassel <niklas.cassel@xxxxxxxx>

Previously, dw_pcie_ep_set_msi() wrote all bits in the Message Control
register, thus overwriting the PCI_MSI_FLAGS_64BIT bit.
By clearing the PCI_MSI_FLAGS_64BIT bit, we break MSI
on systems where the RC has set a 64 bit MSI address.
Fix dw_pcie_ep_set_msi() so that it only sets MMC bits.

Tested-by: Gustavo Pimentel <gustavo.pimentel@xxxxxxxxxxxx>
Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxxx>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Acked-by: Joao Pinto <jpinto@xxxxxxxxxxxx>
(cherry picked from commit 099a95f3591ade29da52131895a3ba9f92a0e82c)
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
 drivers/pci/dwc/pcie-designware-ep.c | 4 +++-
 drivers/pci/dwc/pcie-designware.h    | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c
index 7c621877a939..df317d390317 100644
--- a/drivers/pci/dwc/pcie-designware-ep.c
+++ b/drivers/pci/dwc/pcie-designware-ep.c
@@ -214,7 +214,9 @@ static int dw_pcie_ep_set_msi(struct pci_epc *epc, u8 encode_int)
 	struct dw_pcie_ep *ep = epc_get_drvdata(epc);
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 
-	val = (encode_int << MSI_CAP_MMC_SHIFT);
+	val = dw_pcie_readw_dbi(pci, MSI_MESSAGE_CONTROL);
+	val &= ~MSI_CAP_MMC_MASK;
+	val |= (encode_int << MSI_CAP_MMC_SHIFT) & MSI_CAP_MMC_MASK;
 	dw_pcie_writew_dbi(pci, MSI_MESSAGE_CONTROL, val);
 
 	return 0;
diff --git a/drivers/pci/dwc/pcie-designware.h b/drivers/pci/dwc/pcie-designware.h
index 3551dd607b90..5af29d125c7e 100644
--- a/drivers/pci/dwc/pcie-designware.h
+++ b/drivers/pci/dwc/pcie-designware.h
@@ -99,6 +99,7 @@
 
 #define MSI_MESSAGE_CONTROL		0x52
 #define MSI_CAP_MMC_SHIFT		1
+#define MSI_CAP_MMC_MASK		(7 << MSI_CAP_MMC_SHIFT)
 #define MSI_CAP_MME_SHIFT		4
 #define MSI_CAP_MSI_EN_MASK		0x1
 #define MSI_CAP_MME_MASK		(7 << MSI_CAP_MME_SHIFT)
-- 
2.20.0