PCI: imx6: Fix link training status detection in link up check

This bug was introduced in the interaction for two commits on either
branch of the merge commit 562df5c8 ("Merge branch
'pci/host-designware' into next").

Commit 4d107d3b ("PCI: imx6: Move link up check into
imx6_pcie_wait_for_link()"), changed imx6_pcie_wait_for_link() to poll
the link status register directly, checking for link up and not
training, and made imx6_pcie_link_up() only check the link up bit (once,
not a polling loop).

While commit 886bc5ce ("PCI: designware: Add generic
dw_pcie_wait_for_link()"), replaced the loop in
imx6_pcie_wait_for_link() with a call to a new dwc core function, which
polled imx6_pcie_link_up(), which still checked both link up and not
training in a loop.

When these two commits were merged, the version of
imx6_pcie_wait_for_link() from 886bc5ce was kept, which eliminated
the link training check placed there by 4d107d3b. However, the
version of imx6_pcie_link_up() from 4d107d3b was kept, which
eliminated the link training check that had been there and was moved to
imx6_pcie_wait_for_link().

The result was the link training check got lost for the imx6 driver.

Eliminate imx6_pcie_link_up() so that the default handler,
dw_pcie_link_up(), is used instead. The default handler has the correct
code, which checks for link up and also that it still is not training,
fixing the regression.

Fixes: 562df5c8 ("Merge branch 'pci/host-designware' into next")
Signed-off-by: Trent Piepho <tpiepho@impinj.com>
[lorenzo.pieralisi@arm.com: rewrote the commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Joao Pinto <Joao.Pinto@synopsys.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Richard Zhu <hongxing.zhu@nxp.com>

drivers/pci/controller/dwc/pci-imx6.c

@@ -81,8 +81,6 @@ struct imx6_pcie {
 #define PCIE_PL_PFLR_FORCE_LINK			(1 << 15)
 #define PCIE_PHY_DEBUG_R0 (PL_OFFSET + 0x28)
 #define PCIE_PHY_DEBUG_R1 (PL_OFFSET + 0x2c)
-#define PCIE_PHY_DEBUG_R1_XMLH_LINK_IN_TRAINING	(1 << 29)
-#define PCIE_PHY_DEBUG_R1_XMLH_LINK_UP		(1 << 4)
 
 #define PCIE_PHY_CTRL (PL_OFFSET + 0x114)
 #define PCIE_PHY_CTRL_DATA_LOC 0
@@ -711,12 +709,6 @@ static int imx6_pcie_host_init(struct pcie_port *pp)
 	return 0;
 }
 
-static int imx6_pcie_link_up(struct dw_pcie *pci)
-{
-	return dw_pcie_readl_dbi(pci, PCIE_PHY_DEBUG_R1) &
-			PCIE_PHY_DEBUG_R1_XMLH_LINK_UP;
-}
-
 static const struct dw_pcie_host_ops imx6_pcie_host_ops = {
 	.host_init = imx6_pcie_host_init,
 };
@@ -749,7 +741,7 @@ static int imx6_add_pcie_port(struct imx6_pcie *imx6_pcie,
 }
 
 static const struct dw_pcie_ops dw_pcie_ops = {
-	.link_up = imx6_pcie_link_up,
+	/* No special ops needed, but pcie-designware still expects this struct */
 };
 
 #ifdef CONFIG_PM_SLEEP