[PATCH v4 13/17] PCI: imx6: Do not wait for speed change on i.MX7

[Andrey Smirnov <andrew.smirnov@gmail.com>]

Port of a Linux commit e6dcd87fff69a9d454104b65569074855cf95b1e

  As can be seen from [1]:

    "...the different behavior between iMX6Q PCIe and iMX7D PCIe maybe caused
    by the different controller version.

    Regarding to the DOC description, the DIRECT_SPEED_CHANGE should be
    cleared after the speed change from GEN1 to GEN2. Unfortunately, when
    GEN1 device is used, the behavior is not documented.

    So, IC design guys run the simulation and find out the following
    behaviors:

       1. DIRECT_SPEED_CHANGE will be cleared in 7D after speed change
          from GEN1 to GEN2. This matches doc’s description

       2. set MAX link speed(PCIE_CAP_TARGET_LINK_SPEED=0x01) as GEN1 and
          re-run the simulation, DIRECT_SPEED_CHANGE will not be cleared;
          remain as 1, this matches your result, but function test is
          passed, so this bit should not affect the normal PCIe function."

  imx6_pcie_wait_for_speed_change() will report false failures for Gen1 ->
  Gen1 speed transition, so avoid doing that check and just rely on
  imx6_pcie_wait_for_link() only.

  [1] https://community.nxp.com/message/867943

  Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
  Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
  Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
  Cc: yurovsky@gmail.com
  Cc: Fabio Estevam <fabio.estevam@nxp.com>
  Cc: Dong Aisheng <dongas86@gmail.com>
  Cc: linux-arm-kernel@lists.infradead.org

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---
 drivers/pci/pci-imx6.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/pci-imx6.c b/drivers/pci/pci-imx6.c
index ce68b007ab..d121a20ce1 100644
--- a/drivers/pci/pci-imx6.c
+++ b/drivers/pci/pci-imx6.c
@@ -508,10 +508,21 @@ static int imx6_pcie_establish_link(struct imx6_pcie *imx6_pcie)
 	tmp |= PORT_LOGIC_SPEED_CHANGE;
 	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, tmp);
 
-	ret = imx6_pcie_wait_for_speed_change(imx6_pcie);
-	if (ret) {
-		dev_err(dev, "Failed to bring link up!\n");
-		goto err_reset_phy;
+	if (imx6_pcie->variant != IMX7D) {
+		/*
+		 * On i.MX7, DIRECT_SPEED_CHANGE behaves differently
+		 * from i.MX6 family when no link speed transition
+		 * occurs and we go Gen1 -> yep, Gen1. The difference
+		 * is that, in such case, it will not be cleared by HW
+		 * which will cause the following code to report false
+		 * failure.
+		 */
+
+		ret = imx6_pcie_wait_for_speed_change(imx6_pcie);
+		if (ret) {
+			dev_err(dev, "Failed to bring link up!\n");
+			goto err_reset_phy;
+		}
 	}
 
 	/* Make sure link training is finished as well! */
-- 
2.20.1


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