Both earlycon and earlyprintk depend on the bootloader setup UART
clocks being retained. This patch adds the common logic to detect such
situations and make the information available to the clock drivers, as
well as adding the facilities to disable those clocks at the end of
the kernel init.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/clk/imx/clk.c | 38 ++++++++++++++++++++++++++++++++++++++
 drivers/clk/imx/clk.h |  1 +
 2 files changed, 39 insertions(+)

diff --git a/drivers/clk/imx/clk.c b/drivers/clk/imx/clk.c
index df12b5307175..45a073dab435 100644
--- a/drivers/clk/imx/clk.c
+++ b/drivers/clk/imx/clk.c

@@ -73,3 +73,41 @@ void imx_cscmr1_fixup(u32 *val)
 	*val ^= CSCMR1_FIXUP;
 	return;
 }
+
+static int imx_keep_uart_clocks __initdata;
+static struct clk ** const *imx_uart_clocks __initdata;
+
+static int __init imx_keep_uart_clocks_param(char *str)
+{
+	imx_keep_uart_clocks = 1;
+
+	return 0;
+}
+__setup_param("earlycon", imx_keep_uart_earlycon,
+	      imx_keep_uart_clocks_param, 0);
+__setup_param("earlyprintk", imx_keep_uart_earlyprintk,
+	      imx_keep_uart_clocks_param, 0);
+
+void __init imx_register_uart_clocks(struct clk ** const clks[])
+{
+	if (imx_keep_uart_clocks) {
+		int i;
+
+		imx_uart_clocks = clks;
+		for (i = 0; imx_uart_clocks[i]; i++)
+			clk_prepare_enable(*imx_uart_clocks[i]);
+	}
+}
+
+static int __init imx_clk_disable_uart(void)
+{
+	if (imx_keep_uart_clocks) {
+		int i;
+
+		for (i = 0; imx_uart_clocks[i]; i++)
+			clk_disable_unprepare(*imx_uart_clocks[i]);
+	}
+
+	return 0;
+}
+late_initcall_sync(imx_clk_disable_uart);