[PATCH 5.11 592/775] phy: lantiq: rcu-usb2: wait after clock enable

[Greg Kroah-Hartman]

From: Mathias Kresin <dev@xxxxxxxxx>

commit 36acd5e24e3000691fb8d1ee31cf959cb1582d35 upstream.

Commit 65dc2e725286 ("usb: dwc2: Update Core Reset programming flow.")
revealed that the phy isn't ready immediately after enabling it's
clocks. The dwc2_check_core_version() fails and the dwc2 usb driver
errors out.

Add a short delay to let the phy get up and running. There isn't any
documentation how much time is required, the value was chosen based on
tests.

Signed-off-by: Mathias Kresin <dev@xxxxxxxxx>
Acked-by: Hauke Mehrtens <hauke@xxxxxxxxxx>
Acked-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v5.7+
Link: https://lore.kernel.org/r/20210107224901.2102479-1-dev@xxxxxxxxx
Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/phy/lantiq/phy-lantiq-rcu-usb2.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/drivers/phy/lantiq/phy-lantiq-rcu-usb2.c
+++ b/drivers/phy/lantiq/phy-lantiq-rcu-usb2.c
@@ -124,8 +124,16 @@ static int ltq_rcu_usb2_phy_power_on(str
 	reset_control_deassert(priv->phy_reset);
 
 	ret = clk_prepare_enable(priv->phy_gate_clk);
-	if (ret)
+	if (ret) {
 		dev_err(dev, "failed to enable PHY gate\n");
+		return ret;
+	}
+
+	/*
+	 * at least the xrx200 usb2 phy requires some extra time to be
+	 * operational after enabling the clock
+	 */
+	usleep_range(100, 200);
 
 	return ret;
 }