[v4] PCI: imx: make msi work without CONFIG_PCIEPORTBUS=y

[Richard Zhu]

Assertion of the MSI Enable bit of RC's MSI CAP is mandatory required to
trigger MSI on i.MX6 PCIe.
This bit would be asserted when CONFIG_PCIEPORTBUS=y.
Thus, the MSI works fine on i.MX6 PCIe before the commit "f3fdfc4".

Assert it unconditionally when MSI is enabled.
Otherwise, the MSI wouldn't be triggered although the EP is present and
the MSIs are assigned.

Signed-off-by: Richard Zhu <hongxing.zhu@xxxxxxx>
Reviewed-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
---
Changes v1 -> v2:
* Assert the MSI_EN unconditionally when MSI is supported.
Changes v2 -> v3:
* Remove the IS_ENABLED(CONFIG_PCI_MSI) since the driver depends on
PCI_MSI_IRQ_DOMAIN
* Extended with a check for pci_msi_enabled() to see if the user
explicitly want legacy IRQs
Changes v3 -> v4:
* Refer to Bjorn's comments, refine the subject and commit log and change
the PCI_MSI_CAP to PCIE_RC_IMX6_MSI_CAP.
---
 drivers/pci/controller/dwc/pci-imx6.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 26087b3..639bb27 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -74,6 +74,7 @@ struct imx6_pcie {
 #define PHY_PLL_LOCK_WAIT_USLEEP_MAX	200
 
 /* PCIe Root Complex registers (memory-mapped) */
+#define PCIE_RC_IMX6_MSI_CAP			0x50
 #define PCIE_RC_LCR				0x7c
 #define PCIE_RC_LCR_MAX_LINK_SPEEDS_GEN1	0x1
 #define PCIE_RC_LCR_MAX_LINK_SPEEDS_GEN2	0x2
@@ -926,6 +927,7 @@ static int imx6_pcie_probe(struct platform_device *pdev)
 	struct resource *dbi_base;
 	struct device_node *node = dev->of_node;
 	int ret;
+	u16 val;
 
 	imx6_pcie = devm_kzalloc(dev, sizeof(*imx6_pcie), GFP_KERNEL);
 	if (!imx6_pcie)
@@ -1071,6 +1073,14 @@ static int imx6_pcie_probe(struct platform_device *pdev)
 	if (ret < 0)
 		return ret;
 
+	if (pci_msi_enabled()) {
+		val = dw_pcie_readw_dbi(pci, PCIE_RC_IMX6_MSI_CAP +
+				PCI_MSI_FLAGS);
+		val |= PCI_MSI_FLAGS_ENABLE;
+		dw_pcie_writew_dbi(pci, PCIE_RC_MSI_IMX6_CAP +
+				PCI_MSI_FLAGS, val);
+	}
+
 	return 0;
 }
 
-- 
2.7.4