[PATCH 3/4] usb: chipidea: imx: call enable_clk after all resources are requested

[Marco Felsch <m.felsch@pengutronix.de>]

Currently we enable the clock immediately after requesting it and leave
it on the whole time. Afterwards if the phy request is failing we leave
the usb-controller <-> usb-phy connection in a partly initialized state.
At least on i.MX8M SoCs this can cause strange system hangs during boot.

The (more) correct way would be to have the whole power-domain framework
and the blk-ctrl driver support within barebox. So we can leave the
power-domain in a known good state for linux. Since this is not the case
we can move the clk_enable() call so it gets called after we know that
all ressources are available. So the probability to leave the system in
a partly initialized state is lesser.

Drop the !IS_ERR() since NULL and errors are handled in clk_enable() as
well.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
---
 drivers/usb/imx/chipidea-imx.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/imx/chipidea-imx.c b/drivers/usb/imx/chipidea-imx.c
index bf8b6f1eb8..f71cf80b7d 100644
--- a/drivers/usb/imx/chipidea-imx.c
+++ b/drivers/usb/imx/chipidea-imx.c
@@ -260,8 +260,6 @@ static int imx_chipidea_probe(struct device_d *dev)
 	 * devices which have only one.
 	 */
 	ci->clk = clk_get(dev, NULL);
-	if (!IS_ERR(ci->clk))
-		clk_enable(ci->clk);
 
 	/* Device trees are using both "phys" and "fsl,usbphy".  Prefer the
 	 * more modern former one but fall back to the old one.
@@ -302,6 +300,14 @@ static int imx_chipidea_probe(struct device_d *dev)
 	ci->data.drvdata = ci;
 	ci->data.usbphy = ci->usbphy;
 
+	/*
+	 * Enable the clock after we ensured that all resources are available.
+	 * This is crucial since the phy can be missing which and so the
+	 * usb-controller <-> usb-phy communication is only partly initialized.
+	 * This can trigger strange system hangs at least on i.MX8M SoCs.
+	 */
+	clk_enable(ci->clk);
+
 	if ((ci->flags & MXC_EHCI_PORTSC_MASK) == MXC_EHCI_MODE_HSIC)
 		imx_chipidea_port_init(ci);
 
-- 
2.30.2