[PATCH V2] ARM: imx: correct usecount of IPG, ARM and MMDC clk on i.mx6sl

[Anson Huang]

IPG, ARM and MMDC's clock should be enabled during kernel boot up,
so we need to maintain their use count, otherwise, they may be
disabled unexpectedly if their children's clock are turned off,
which is not allowed.

Signed-off-by: Anson Huang <b20788 at freescale.com>
---
 arch/arm/mach-imx/clk-imx6sl.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/arm/mach-imx/clk-imx6sl.c b/arch/arm/mach-imx/clk-imx6sl.c
index 78f3bd6..047f4ff 100644
--- a/arch/arm/mach-imx/clk-imx6sl.c
+++ b/arch/arm/mach-imx/clk-imx6sl.c
@@ -291,6 +291,22 @@ static void __init imx6sl_clocks_init(struct device_node *ccm_node)
 		pr_warn("%s: failed to set AHB clock rate %d!\n",
 			__func__, ret);
 
+	/*
+	 * Make sure those always on clocks are enabled to maintain the correct
+	 * usecount and enabling/disabling of parent PLLs.
+	 */
+	ret = clk_prepare_enable(clks[IMX6SL_CLK_IPG]);
+	if (ret)
+		pr_warn("%s: failed to enable IPG clock %d\n", __func__, ret);
+
+	ret = clk_prepare_enable(clks[IMX6SL_CLK_ARM]);
+	if (ret)
+		pr_warn("%s: failed to enable ARM clock %d\n", __func__, ret);
+
+	ret = clk_prepare_enable(clks[IMX6SL_CLK_MMDC_ROOT]);
+	if (ret)
+		pr_warn("%s: failed to enable MMDC clock %d\n", __func__, ret);
+
 	if (IS_ENABLED(CONFIG_USB_MXS_PHY)) {
 		clk_prepare_enable(clks[IMX6SL_CLK_USBPHY1_GATE]);
 		clk_prepare_enable(clks[IMX6SL_CLK_USBPHY2_GATE]);
-- 
1.7.9.5