PCI: designware-ep: dw_pcie_ep_set_msi() should only set MMC bits

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@synopsys.com>
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Joao Pinto <jpinto@synopsys.com>

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

@@ -220,7 +220,9 @@ 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;

drivers/pci/dwc/pcie-designware.h

@@ -101,6 +101,7 @@
 
 #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_MME_MASK		(7 << MSI_CAP_MME_SHIFT)
 #define MSI_MESSAGE_ADDR_L32		0x54