rockchip: clk: rk3399: add clk_enable function and support USB HOST0/1

The generic ehci-driver (ehci-generic.c) will try to enable the clocks
listed in the DTSI. If this fails (e.g. due to clk_enable not being
implemented in a driver and -ENOSYS being returned by the clk-uclass),
the driver will bail our and print an error message.

This implements a minimal clk_enable for the RK3399 and supports the
clocks mandatory for the EHCI controllers; as these are enabled by
default we simply return success.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/clk/rockchip/clk_rk3399.c

@@ -950,9 +950,24 @@ static ulong rk3399_clk_set_rate(struct clk *clk, ulong rate)
 	return ret;
 }
 
+static int rk3399_clk_enable(struct clk *clk)
+{
+	switch (clk->id) {
+	case HCLK_HOST0:
+	case HCLK_HOST0_ARB:
+	case HCLK_HOST1:
+	case HCLK_HOST1_ARB:
+		return 0;
+	}
+
+	debug("%s: unsupported clk %ld\n", __func__, clk->id);
+	return -ENOENT;
+}
+
 static struct clk_ops rk3399_clk_ops = {
 	.get_rate = rk3399_clk_get_rate,
 	.set_rate = rk3399_clk_set_rate,
+	.enable = rk3399_clk_enable,
 };
 
 static int rk3399_clk_probe(struct udevice *dev)