[PATCH v6 2/4] PCI: imx6: Do not wait for speed change on i.MX7

Andrey Smirnov andrew.smirnov at gmail.com
Tue Mar 14 08:18:25 PDT 2017

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

Cc: yurovsky at gmail.com
Cc: Lucas Stach <l.stach at pengutronix.de>
Cc: Bjorn Helgaas <bhelgaas at google.com>
Cc: Fabio Estevam <fabio.estevam at nxp.com>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Andrey Smirnov <andrew.smirnov at gmail.com>
 drivers/pci/host/pci-imx6.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index 2f3f375..473bbdc 100644
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -577,10 +577,21 @@ static int imx6_pcie_establish_link(struct imx6_pcie *imx6_pcie)
 	dw_pcie_writel_rc(pp, 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! */

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