Both earlycon and eralyprintk 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 | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/clk/imx/clk.h |  1 +
 2 files changed, 47 insertions(+)

diff --git a/drivers/clk/imx/clk.c b/drivers/clk/imx/clk.c
index df12b5307175..3357e29e43ab 100644
--- a/drivers/clk/imx/clk.c
+++ b/drivers/clk/imx/clk.c

@@ -73,3 +73,49 @@ void imx_cscmr1_fixup(u32 *val)
 	*val ^= CSCMR1_FIXUP;
 	return;
 }
+
+static int __initdata imx_keep_uart_clocks;

+static struct clk __initdata ***imx_uart_clocks;
+
+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 **clks[])
+{
+	if (imx_keep_uart_clocks) {
+		int i;
+
+		imx_uart_clocks = clks;
+		for (i = 0;; i++) {
+			if (imx_uart_clocks[i])
+				clk_prepare_enable(*imx_uart_clocks[i]);
+			else
+				break;
+		}
+	}
+}
+
+static int __init imx_clk_disable_uart(void)
+{
+	if (imx_keep_uart_clocks) {
+		int i;
+
+		for (i = 0;; i++) {
+			if (imx_uart_clocks[i])
+				clk_disable_unprepare(*imx_uart_clocks[i]);
+			else
+				break;
+		}
+	}
+
+	return 0;
+}
+late_initcall_sync(imx_clk_disable_uart);

diff --git a/drivers/clk/imx/clk.h b/drivers/clk/imx/clk.h
index 1049b0c7d818..c4e2e282e892 100644
--- a/drivers/clk/imx/clk.h
+++ b/drivers/clk/imx/clk.h

@@ -7,6 +7,7 @@
 extern spinlock_t imx_ccm_lock;
 
 void imx_check_clocks(struct clk *clks[], unsigned int count);
+void imx_register_uart_clocks(struct clk **clks[]);
 
 extern void imx_cscmr1_fixup(u32 *val);
 

-- 
2.5.0