clk: imx: Fix reparenting of UARTs not associated with stdout

Most if not all i.MX SoC's call a function which enables all UARTS.
This is a problem for users who need to re-parent the clock source,
because any attempt to change the parent results in an busy error
due to the fact that the clocks have been enabled already.

  clk: failed to reparent uart1 to sys_pll1_80m: -16

Instead of pre-initializing all UARTS, scan the device tree to see
which UART clocks are associated to stdout, and only enable those
UART clocks if it's needed early.  This will move initialization of
the remaining clocks until after the parenting of the clocks.

When the clocks are shutdown, this mechanism will also disable any
clocks that were pre-initialized.

Fixes: 9461f7b33d11c ("clk: fix CLK_SET_RATE_GATE with clock rate protection")
Suggested-by: Aisheng Dong <aisheng.dong@nxp.com>
Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Tested-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Abel Vesa <abel.vesa@nxp.com>

1 files changed, 32 insertions, 9 deletions

diff --git a/drivers/clk/imx/clk.c b/drivers/clk/imx/clk.c
index 47882c51cb85..7cc669934253 100644
--- a/drivers/clk/imx/clk.c
+++ b/drivers/clk/imx/clk.c
@@ -147,8 +147,10 @@ void imx_cscmr1_fixup(u32 *val)
 }
 
 #ifndef MODULE
-static int imx_keep_uart_clocks;
-static struct clk ** const *imx_uart_clocks;
+
+static bool imx_keep_uart_clocks;
+static int imx_enabled_uart_clocks;
+static struct clk **imx_uart_clocks;
 
 static int __init imx_keep_uart_clocks_param(char *str)
 {
@@ -161,24 +163,45 @@ __setup_param("earlycon", imx_keep_uart_earlycon,
 __setup_param("earlyprintk", imx_keep_uart_earlyprintk,
 	      imx_keep_uart_clocks_param, 0);
 
-void imx_register_uart_clocks(struct clk ** const clks[])
+void imx_register_uart_clocks(unsigned int clk_count)
 {
+	imx_enabled_uart_clocks = 0;
+
+/* i.MX boards use device trees now.  For build tests without CONFIG_OF, do nothing */
+#ifdef CONFIG_OF
 	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]);
+		imx_uart_clocks = kcalloc(clk_count, sizeof(struct clk *), GFP_KERNEL);
+
+		if (!of_stdout)
+			return;
+
+		for (i = 0; i < clk_count; i++) {
+			imx_uart_clocks[imx_enabled_uart_clocks] = of_clk_get(of_stdout, i);
+
+			/* Stop if there are no more of_stdout references */
+			if (IS_ERR(imx_uart_clocks[imx_enabled_uart_clocks]))
+				return;
+
+			/* Only enable the clock if it's not NULL */
+			if (imx_uart_clocks[imx_enabled_uart_clocks])
+				clk_prepare_enable(imx_uart_clocks[imx_enabled_uart_clocks++]);
+		}
 	}
+#endif
 }
 
 static int __init imx_clk_disable_uart(void)
 {
-	if (imx_keep_uart_clocks && imx_uart_clocks) {
+	if (imx_keep_uart_clocks && imx_enabled_uart_clocks) {
 		int i;
 
-		for (i = 0; imx_uart_clocks[i]; i++)
-			clk_disable_unprepare(*imx_uart_clocks[i]);
+		for (i = 0; i < imx_enabled_uart_clocks; i++) {
+			clk_disable_unprepare(imx_uart_clocks[i]);
+			clk_put(imx_uart_clocks[i]);
+		}
+		kfree(imx_uart_clocks);
 	}
 
 	return 0;