[PATCH] PCI: dwc: Set PORT_LOGIC_LINK_WIDTH to one lane

[Wenbin Yao (Consultant)]

PORT_LOGIC_LINK_WIDTH field of the PCIE_LINK_WIDTH_SPEED_CONTROL register
indicates the number of lanes to check for exit from Electrical Idle in
Polling.Active and L2.Idle. It is used to limit the effective link width to
ignore broken or unused lanes that detect a receiver to prevent one or more
bad Receivers or Transmitters from holding up a valid Link from being
configured.

In a PCIe link that support muiltiple lanes, setting PORT_LOGIC_LINK_WIDTH
to 1 will not affect the link width that is actually intended to be used.
But setting it to a value other than 1 will lead to link training fail if
one or more lanes are broken.

Hence, always set PORT_LOGIC_LINK_WIDTH to 1 no matter how many lanes the
port actually supports to make linking up more robust. Link can still be
established with one lane at least if other lanes are broken.

Signed-off-by: Wenbin Yao <quic_wenbyao@xxxxxxxxxxx>
---
 drivers/pci/controller/dwc/pcie-designware.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c 
b/drivers/pci/controller/dwc/pcie-designware.c
index 6d6cbc8b5b2c..d40afe74ddd1 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -752,22 +752,19 @@ static void dw_pcie_link_set_max_link_width(struct 
dw_pcie *pci, u32 num_lanes)
     /* Set link width speed control register */
     lwsc = dw_pcie_readl_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL);
     lwsc &= ~PORT_LOGIC_LINK_WIDTH_MASK;
+    lwsc |= PORT_LOGIC_LINK_WIDTH_1_LANES;
     switch (num_lanes) {
     case 1:
         plc |= PORT_LINK_MODE_1_LANES;
-        lwsc |= PORT_LOGIC_LINK_WIDTH_1_LANES;
         break;
     case 2:
         plc |= PORT_LINK_MODE_2_LANES;
-        lwsc |= PORT_LOGIC_LINK_WIDTH_2_LANES;
         break;
     case 4:
         plc |= PORT_LINK_MODE_4_LANES;
-        lwsc |= PORT_LOGIC_LINK_WIDTH_4_LANES;
         break;
     case 8:
         plc |= PORT_LINK_MODE_8_LANES;
-        lwsc |= PORT_LOGIC_LINK_WIDTH_8_LANES;
         break;
     default:
         dev_err(pci->dev, "num-lanes %u: invalid value\n", num_lanes);
--
2.34.1