[PATCH] pci: fix incorrect value returned from pcie_get_speed_cap

[Mikulas Patocka]

The macros PCI_EXP_LNKCAP_SLS_*GB are values, not bit masks. We must mask
the register and compare it against them.

This patch fixes errors "amdgpu: [powerplay] failed to send message 261
ret is 0" errors when PCIe-v3 card is plugged into PCIe-v1 slot, because
the slot is being incorrectly reported as PCIe-v3 capable.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
Fixes: 6cf57be0f78e ("PCI: Add pcie_get_speed_cap() to find max supported link speed")
Cc: stable at vger.kernel.org	# v4.17+

---
 drivers/pci/pci.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Index: linux-4.19/drivers/pci/pci.c
===================================================================
--- linux-4.19.orig/drivers/pci/pci.c	2018-10-30 16:58:58.000000000 +0100
+++ linux-4.19/drivers/pci/pci.c	2018-10-30 16:58:58.000000000 +0100
@@ -5492,13 +5492,13 @@ enum pci_bus_speed pcie_get_speed_cap(st
 
 	pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
 	if (lnkcap) {
-		if (lnkcap & PCI_EXP_LNKCAP_SLS_16_0GB)
+		if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_16_0GB)
 			return PCIE_SPEED_16_0GT;
-		else if (lnkcap & PCI_EXP_LNKCAP_SLS_8_0GB)
+		else if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_8_0GB)
 			return PCIE_SPEED_8_0GT;
-		else if (lnkcap & PCI_EXP_LNKCAP_SLS_5_0GB)
+		else if ((lnkcap & PCI_EXP_LNKCAP_SLS) ==PCI_EXP_LNKCAP_SLS_5_0GB)
 			return PCIE_SPEED_5_0GT;
-		else if (lnkcap & PCI_EXP_LNKCAP_SLS_2_5GB)
+		else if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_2_5GB)
 			return PCIE_SPEED_2_5GT;
 	}