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, 2 insertions, 16 deletions

diff --git a/drivers/clk/imx/clk-imx8mm.c b/drivers/clk/imx/clk-imx8mm.c
index 6a01eec36dd0..f1919fafb124 100644
--- a/drivers/clk/imx/clk-imx8mm.c
+++ b/drivers/clk/imx/clk-imx8mm.c
@@ -296,20 +296,12 @@ static const char * const clkout_sels[] = {"audio_pll1_out", "audio_pll2_out", "
 static struct clk_hw_onecell_data *clk_hw_data;
 static struct clk_hw **hws;
 
-static const int uart_clk_ids[] = {
-	IMX8MM_CLK_UART1_ROOT,
-	IMX8MM_CLK_UART2_ROOT,
-	IMX8MM_CLK_UART3_ROOT,
-	IMX8MM_CLK_UART4_ROOT,
-};
-static struct clk **uart_hws[ARRAY_SIZE(uart_clk_ids) + 1];
-
 static int imx8mm_clocks_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct device_node *np = dev->of_node;
 	void __iomem *base;
-	int ret, i;
+	int ret;
 
 	clk_hw_data = kzalloc(struct_size(clk_hw_data, hws,
 					  IMX8MM_CLK_END), GFP_KERNEL);
@@ -634,13 +626,7 @@ static int imx8mm_clocks_probe(struct platform_device *pdev)
 		goto unregister_hws;
 	}
 
-	for (i = 0; i < ARRAY_SIZE(uart_clk_ids); i++) {
-		int index = uart_clk_ids[i];
-
-		uart_hws[i] = &hws[index]->clk;
-	}
-
-	imx_register_uart_clocks(uart_hws);
+	imx_register_uart_clocks(4);
 
 	return 0;