[PATCH v2] PCI: designware-ep: Fix ->get_msi() to check MSI_EN bit

[Kishon Vijay Abraham I]

->get_msi() now checks MSI_EN bit in the MSI CAPABILITY register to
find whether the host supports MSI instead of using the
MSI ADDRESS in the MSI CAPABILITY register.

This fixes the issue with the following sequence
  'modprobe pci_endpoint_test' enables MSI
  'rmmod pci_endpoint_test' disables MSI but MSI address (in EP's
	capability register) has a valid value
  'modprobe pci_endpoint_test no_msi=1' - Since MSI address (in EP's
	capability register) has a valid value (set during the previous
	insertion of the module), EP thinks host supports MSI.

Fixes: f8aed6ec624fb436 ("PCI: dwc: designware: Add EP mode support")
Signed-off-by: Kishon Vijay Abraham I <kishon@xxxxxx>
---
changes from v1:
Added a Fixes tag and mentioned MSI address to be set in EP's capability
register in the commit log.

 drivers/pci/dwc/pcie-designware-ep.c | 12 +++---------
 drivers/pci/dwc/pcie-designware.h    |  1 +
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c
index d53d5f168363..7c621877a939 100644
--- a/drivers/pci/dwc/pcie-designware-ep.c
+++ b/drivers/pci/dwc/pcie-designware-ep.c
@@ -197,20 +197,14 @@ static int dw_pcie_ep_map_addr(struct pci_epc *epc, phys_addr_t addr,
 static int dw_pcie_ep_get_msi(struct pci_epc *epc)
 {
 	int val;
-	u32 lower_addr;
-	u32 upper_addr;
 	struct dw_pcie_ep *ep = epc_get_drvdata(epc);
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 
-	val = dw_pcie_readb_dbi(pci, MSI_MESSAGE_CONTROL);
-	val = (val & MSI_CAP_MME_MASK) >> MSI_CAP_MME_SHIFT;
-
-	lower_addr = dw_pcie_readl_dbi(pci, MSI_MESSAGE_ADDR_L32);
-	upper_addr = dw_pcie_readl_dbi(pci, MSI_MESSAGE_ADDR_U32);
-
-	if (!(lower_addr || upper_addr))
+	val = dw_pcie_readw_dbi(pci, MSI_MESSAGE_CONTROL);
+	if (!(val & MSI_CAP_MSI_EN_MASK))
 		return -EINVAL;
 
+	val = (val & MSI_CAP_MME_MASK) >> MSI_CAP_MME_SHIFT;
 	return val;
 }
 
diff --git a/drivers/pci/dwc/pcie-designware.h b/drivers/pci/dwc/pcie-designware.h
index e5d9d77b778e..cb493bcae8b4 100644
--- a/drivers/pci/dwc/pcie-designware.h
+++ b/drivers/pci/dwc/pcie-designware.h
@@ -101,6 +101,7 @@
 #define MSI_MESSAGE_CONTROL		0x52
 #define MSI_CAP_MMC_SHIFT		1
 #define MSI_CAP_MME_SHIFT		4
+#define MSI_CAP_MSI_EN_MASK		0x1
 #define MSI_CAP_MME_MASK		(7 << MSI_CAP_MME_SHIFT)
 #define MSI_MESSAGE_ADDR_L32		0x54
 #define MSI_MESSAGE_ADDR_U32		0x58
-- 
2.11.0