clk: rockchip: only enter pll slow-mode directly before reboots on rk3288

As commit 1d33929e2a2b ("clk: rockchip: switch PLLs to slow mode before
reboot for rk3288") states, switching the PLLs to slow-mode is only
necessary when rebooting using the soft-reset done through the CRU.

The dwc2 controllers used create really big number of interrupts in
special constellations involving usb-hubs and their number is so high,
it can even overwhelm the interrupt handler if the cpu-speed os to low.

Right now the PLLs are put into slow-mode in a shutdown syscore_ops
callback which means it happens on all reboots (not only the soft-reset
ones) and even on poweroff actions.

This can result in the system not powering off and getting stuck instead,
so we should move the slow-mode change nearer to the actual reboot action.

For this we introduce the possiblity to also set a callback that gets
called from the restart-handler directly prior to restarting the system
and move the shutdown-callback to this new option.

With this the slow-mode switch is done only on the necessary reboots
and also has a smaller possibility of causing artifacts.

Fixes: 1d33929e2a2b ("clk: rockchip: switch PLLs to slow mode before reboot for rk3288")
Signed-off-by: Heiko Stuebner <heiko.stuebner@collabora.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>

drivers/clk/rockchip/clk-rk3036.c

@@ -473,6 +473,6 @@ static void __init rk3036_clk_init(struct device_node *np)
 	rockchip_register_softrst(np, 9, reg_base + RK2928_SOFTRST_CON(0),
 				  ROCKCHIP_SOFTRST_HIWORD_MASK);
 
-	rockchip_register_restart_notifier(RK2928_GLB_SRST_FST);
+	rockchip_register_restart_notifier(RK2928_GLB_SRST_FST, NULL);
 }
 CLK_OF_DECLARE(rk3036_cru, "rockchip,rk3036-cru", rk3036_clk_init);

drivers/clk/rockchip/clk-rk3188.c

@@ -750,7 +750,7 @@ static void __init rk3188_common_clk_init(struct device_node *np)
 	rockchip_register_softrst(np, 9, reg_base + RK2928_SOFTRST_CON(0),
 				  ROCKCHIP_SOFTRST_HIWORD_MASK);
 
-	rockchip_register_restart_notifier(RK2928_GLB_SRST_FST);
+	rockchip_register_restart_notifier(RK2928_GLB_SRST_FST, NULL);
 }
 
 static void __init rk3066a_clk_init(struct device_node *np)

drivers/clk/rockchip/clk-rk3228.c

@@ -673,6 +673,6 @@ static void __init rk3228_clk_init(struct device_node *np)
 	rockchip_register_softrst(np, 9, reg_base + RK2928_SOFTRST_CON(0),
 				  ROCKCHIP_SOFTRST_HIWORD_MASK);
 
-	rockchip_register_restart_notifier(RK3228_GLB_SRST_FST);
+	rockchip_register_restart_notifier(RK3228_GLB_SRST_FST, NULL);
 }
 CLK_OF_DECLARE(rk3228_cru, "rockchip,rk3228-cru", rk3228_clk_init);

drivers/clk/rockchip/clk-rk3288.c

@@ -848,7 +848,6 @@ static void rk3288_clk_shutdown(void)
 static struct syscore_ops rk3288_clk_syscore_ops = {
 	.suspend = rk3288_clk_suspend,
 	.resume = rk3288_clk_resume,
-	.shutdown = rk3288_clk_shutdown,
 };
 
 static void __init rk3288_clk_init(struct device_node *np)
@@ -906,7 +905,8 @@ static void __init rk3288_clk_init(struct device_node *np)
 				  rk3288_cru_base + RK3288_SOFTRST_CON(0),
 				  ROCKCHIP_SOFTRST_HIWORD_MASK);
 
-	rockchip_register_restart_notifier(RK3288_GLB_SRST_FST);
+	rockchip_register_restart_notifier(RK3288_GLB_SRST_FST,
+					   rk3288_clk_shutdown);
 	register_syscore_ops(&rk3288_clk_syscore_ops);
 }
 CLK_OF_DECLARE(rk3288_cru, "rockchip,rk3288-cru", rk3288_clk_init);

drivers/clk/rockchip/clk-rk3368.c

@@ -889,6 +889,6 @@ static void __init rk3368_clk_init(struct device_node *np)
 	rockchip_register_softrst(np, 15, reg_base + RK3368_SOFTRST_CON(0),
 				  ROCKCHIP_SOFTRST_HIWORD_MASK);
 
-	rockchip_register_restart_notifier(RK3368_GLB_SRST_FST);
+	rockchip_register_restart_notifier(RK3368_GLB_SRST_FST, NULL);
 }
 CLK_OF_DECLARE(rk3368_cru, "rockchip,rk3368-cru", rk3368_clk_init);

drivers/clk/rockchip/clk.c

@@ -341,9 +341,13 @@ void __init rockchip_clk_protect_critical(const char *const clocks[],
 }
 
 static unsigned int reg_restart;
+static void (*cb_restart)(void);
 static int rockchip_restart_notify(struct notifier_block *this,
 				   unsigned long mode, void *cmd)
 {
+	if (cb_restart)
+		cb_restart();
+
 	writel(0xfdb9, reg_base + reg_restart);
 	return NOTIFY_DONE;
 }
@@ -353,11 +357,12 @@ static struct notifier_block rockchip_restart_handler = {
 	.priority = 128,
 };
 
-void __init rockchip_register_restart_notifier(unsigned int reg)
+void __init rockchip_register_restart_notifier(unsigned int reg, void (*cb)(void))
 {
 	int ret;
 
 	reg_restart = reg;
+	cb_restart = cb;
 	ret = register_restart_handler(&rockchip_restart_handler);
 	if (ret)
 		pr_err("%s: cannot register restart handler, %d\n",

drivers/clk/rockchip/clk.h

@@ -503,7 +503,7 @@ void rockchip_clk_register_armclk(unsigned int lookup_id, const char *name,
 			const struct rockchip_cpuclk_rate_table *rates,
 			int nrates);
 void rockchip_clk_protect_critical(const char *const clocks[], int nclocks);
-void rockchip_register_restart_notifier(unsigned int reg);
+void rockchip_register_restart_notifier(unsigned int reg, void (*cb)(void));
 
 #define ROCKCHIP_SOFTRST_HIWORD_MASK	BIT(0)