clk: meson: g12a: mark fclk_div2 as critical

[ Upstream commit 2c4e80e067 ]

On Amlogic Meson G12b platform, similar to fclk_div3, the fclk_div2
seems to be necessary for the system to operate correctly as well.

Typically, the clock also gets chosen by the eMMC peripheral. This
probably masked the problem so far. However, when booting from a SD
card the clock seems to get disabled which leads to a system freeze.

Let's mark this clock as critical, fixing boot from SD card on G12b
platforms.

Fixes: 085a4ea93d ("clk: meson: g12a: add peripheral clock controller")
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Tested-by: Anand Moon <linux.amoon@gmail.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/577e0129e8ee93972d92f13187ff4e4286182f67.1598629915.git.stefan@agner.ch
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/clk/meson/g12a.c

@@ -298,6 +298,17 @@ static struct clk_regmap g12a_fclk_div2 = {
 			&g12a_fclk_div2_div.hw
 		},
 		.num_parents = 1,
+		/*
+		 * Similar to fclk_div3, it seems that this clock is used by
+		 * the resident firmware and is required by the platform to
+		 * operate correctly.
+		 * Until the following condition are met, we need this clock to
+		 * be marked as critical:
+		 * a) Mark the clock used by a firmware resource, if possible
+		 * b) CCF has a clock hand-off mechanism to make the sure the
+		 *    clock stays on until the proper driver comes along
+		 */
+		.flags = CLK_IS_CRITICAL,
 	},
 };