[PATCH] rng: meson: make core clock optional

[Neil Armstrong <narmstrong@baylibre.com>]

This fixes HWRNG support on Amlogic GXL, GXM, G12A, G12B & SM1
based boards dues to the lack of the core clock in the device tree.

It was reported breaking EFI boot in the Linux EFI stub, because the
EFI_RNG_PROTOCOL didn't check for the RNG device presence before
installing itself.

The Linux amlogic,meson-rng.yaml doesn't mandate the core clock,
this the clock should be ignores if not present.

Nevertheless, the clock should be present and this should be fixed
on the Linux meson-gxl.dtsi & meson-g12-common.dtsi then synced
with U-Boot.

The change has been tested on a Khadas VIM3, which uses the common
meson-g12-common.dtsi like the Odroid-C4 & Odroid-N2 in Scott's
report, along with the RNG cmd.

Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reported-by: Scott K Logan <logans@cottsay.net>
Fixes: bc40eb278b ("drivers/rng: add Amlogic hardware RNG driver")
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
---
 drivers/rng/meson-rng.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/rng/meson-rng.c b/drivers/rng/meson-rng.c
index 4b81a62353..57a5a702a2 100644
--- a/drivers/rng/meson-rng.c
+++ b/drivers/rng/meson-rng.c
@@ -90,8 +90,9 @@ static int meson_rng_ofdata_to_platdata(struct udevice *dev)
 	if (!pdata->base)
 		return -ENODEV;
 
+	/* Get optional "core" clock */
 	err = clk_get_by_name(dev, "core", &pdata->clk);
-	if (err)
+	if (err && err != -ENODATA)
 		return err;
 
 	return 0;
-- 
2.22.0