PCI: altera: Fix altera_pcie_link_is_up()

BugLink: https://bugs.launchpad.net/bugs/1818237

commit eff31f40 upstream.

Originally altera_pcie_link_is_up() decided the link was up if any of the
low four bits of the LTSSM register were set.  But the link is only up if
the LTSSM state is L0, so check for that exact value.

[bhelgaas: changelog]
Signed-off-by: Ley Foon Tan <lftan@altera.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Claudius Heine <claudius.heine.ext@siemens.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/pci/host/pcie-altera.c

@@ -40,6 +40,7 @@
 #define P2A_INT_ENABLE			0x3070
 #define P2A_INT_ENA_ALL			0xf
 #define RP_LTSSM			0x3c64
+#define RP_LTSSM_MASK			0x1f
 #define LTSSM_L0			0xf
 
 /* TLP configuration type 0 and 1 */
@@ -140,7 +141,7 @@ static void tlp_write_tx(struct altera_pcie *pcie,
 
 static bool altera_pcie_link_is_up(struct altera_pcie *pcie)
 {
-	return !!(cra_readl(pcie, RP_LTSSM) & LTSSM_L0);
+	return !!((cra_readl(pcie, RP_LTSSM) & RP_LTSSM_MASK) == LTSSM_L0);
 }
 
 static bool altera_pcie_valid_config(struct altera_pcie *pcie,