clk: sunxi-ng: h6: Reparent CPUX during PLL CPUX rate change

[ Upstream commit 7e91ed763dc07437777bd012af7a2bd4493731ff ]

While PLL CPUX clock rate change when CPU is running from it works in
vast majority of cases, now and then it causes instability. This leads
to system crashes and other undefined behaviour. After a lot of testing
(30+ hours) while also doing a lot of frequency switches, we can't
observe any instability issues anymore when doing reparenting to stable
clock like 24 MHz oscillator.

Fixes: 524353ea480b ("clk: sunxi-ng: add support for the Allwinner H6 CCU")
Reported-by: Chad Wagner <wagnerch42@gmail.com>
Link: https://forum.libreelec.tv/thread/27295-orange-pi-3-lts-freezes/
Tested-by: Chad Wagner <wagnerch42@gmail.com>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20231013181712.2128037-1-jernej.skrabec@gmail.com
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-h6.c b/drivers/clk/sunxi-ng/ccu-sun50i-h6.c
index bff446b7829071df891d74dd4a5eda8740cc1c42..2d4fc55718eb4a14ebeda779b08526fb8e2c7237 100644 (file)
--- a/drivers/clk/sunxi-ng/ccu-sun50i-h6.c
+++ b/drivers/clk/sunxi-ng/ccu-sun50i-h6.c
@@ -1181,12 +1181,19 @@ static const u32 usb2_clk_regs[] = {
        SUN50I_H6_USB3_CLK_REG,
 };
 
+static struct ccu_mux_nb sun50i_h6_cpu_nb = {
+       .common         = &cpux_clk.common,
+       .cm             = &cpux_clk.mux,
+       .delay_us       = 1,
+       .bypass_index   = 0, /* index of 24 MHz oscillator */
+};
+
 static int sun50i_h6_ccu_probe(struct platform_device *pdev)
 {
        struct resource *res;
        void __iomem *reg;
+       int i, ret;
        u32 val;
-       int i;
 
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        reg = devm_ioremap_resource(&pdev->dev, res);
@@ -1240,7 +1247,15 @@ static int sun50i_h6_ccu_probe(struct platform_device *pdev)
        val |= BIT(24);
        writel(val, reg + SUN50I_H6_HDMI_CEC_CLK_REG);
 
-       return sunxi_ccu_probe(pdev->dev.of_node, reg, &sun50i_h6_ccu_desc);
+       ret = sunxi_ccu_probe(pdev->dev.of_node, reg, &sun50i_h6_ccu_desc);
+       if (ret)
+               return ret;
+
+       /* Reparent CPU during PLL CPUX rate changes */
+       ccu_mux_notifier_register(pll_cpux_clk.common.hw.clk,
+                                 &sun50i_h6_cpu_nb);
+
+       return 0;
 }
 
 static const struct of_device_id sun50i_h6_ccu_ids[] = {