[PATCH] clk: rockchip: switch PLLs to slow mode before reboot for rk3288

[PATCH] clk: rockchip: switch PLLs to slow mode before reboot for rk3288

[Chris Zhong]

We've been seeing some crashes at reboot test on rk3288-based systems,
which boards have not reset pin connected to NPOR, they reboot by
setting 0xfdb9 to RK3288_GLB_SRST_FST register. If the APLL works in
a high frequency mode, some IPs might hang during soft reset.
It appears that we can fix the problem by switching to slow mode before
reboot, just like what we did before suspend.

Signed-off-by: Chris Zhong <zyw@rock-chips.com>

---

 drivers/clk/rockchip/clk-rk3288.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/clk/rockchip/clk-rk3288.c b/drivers/clk/rockchip/clk-rk3288.c
index 9040878..524662c 100644
--- a/drivers/clk/rockchip/clk-rk3288.c
+++ b/drivers/clk/rockchip/clk-rk3288.c
@@ -16,6 +16,7 @@
 #include <linux/clk-provider.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
+#include <linux/reboot.h>
 #include <linux/syscore_ops.h>
 #include <dt-bindings/clock/rk3288-cru.h>
 #include "clk.h"
@@ -855,6 +856,34 @@ static void rk3288_clk_sleep_init(void __iomem *reg_base)
 static void rk3288_clk_sleep_init(void __iomem *reg_base) {}
 #endif
 
+void __iomem *mode_con_reg;
+static int rk3288_restart_notify(struct notifier_block *this,
+				   unsigned long mode, void *cmd)
+{
+	writel(0xf3030000, mode_con_reg);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block rk3288_restart_handler = {
+	.notifier_call = rk3288_restart_notify,
+	/* Switch PLLs other than DPLL (for SDRAM) to slow mode before reboot
+	 * to avoid crashes in reset, so this priority must bigger than the one
+	 * in rockchip_restart_handler.
+	 */
+	.priority = 129,
+};
+
+void __init rk3288_register_restart_notifier(void __iomem *reg)
+{
+	int ret;
+
+	mode_con_reg = reg;
+	ret = register_restart_handler(&rk3288_restart_handler);
+	if (ret)
+		pr_err("%s: cannot register restart handler, %d\n",
+		       __func__, ret);
+}
+
 static void __init rk3288_clk_init(struct device_node *np)
 {
 	void __iomem *reg_base;
@@ -910,6 +939,8 @@ static void __init rk3288_clk_init(struct device_node *np)
 	rockchip_register_softrst(np, 12, reg_base + RK3288_SOFTRST_CON(0),
 				  ROCKCHIP_SOFTRST_HIWORD_MASK);
 
+	rk3288_register_restart_notifier(reg_base + RK3288_MODE_CON);
+
 	rockchip_register_restart_notifier(RK3288_GLB_SRST_FST);
 	rk3288_clk_sleep_init(reg_base);
 }
-- 
2.6.3

Re: [PATCH] clk: rockchip: switch PLLs to slow mode before reboot for rk3288

[Heiko Stuebner]

Hi Chris,

Am Dienstag, 10. November 2015, 17:35:31 schrieb Chris Zhong:
> We've been seeing some crashes at reboot test on rk3288-based systems,
> which boards have not reset pin connected to NPOR, they reboot by
> setting 0xfdb9 to RK3288_GLB_SRST_FST register. If the APLL works in
> a high frequency mode, some IPs might hang during soft reset.
> It appears that we can fix the problem by switching to slow mode before
> reboot, just like what we did before suspend.
> 
> Signed-off-by: Chris Zhong <zyw@rock-chips.com>
> 
> ---
> 
>  drivers/clk/rockchip/clk-rk3288.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/drivers/clk/rockchip/clk-rk3288.c b/drivers/clk/rockchip/clk-
rk3288.c
> index 9040878..524662c 100644
> --- a/drivers/clk/rockchip/clk-rk3288.c
> +++ b/drivers/clk/rockchip/clk-rk3288.c
> @@ -16,6 +16,7 @@
>  #include <linux/clk-provider.h>
>  #include <linux/of.h>
>  #include <linux/of_address.h>
> +#include <linux/reboot.h>
>  #include <linux/syscore_ops.h>
>  #include <dt-bindings/clock/rk3288-cru.h>
>  #include "clk.h"
> @@ -855,6 +856,34 @@ static void rk3288_clk_sleep_init(void __iomem 
*reg_base)
>  static void rk3288_clk_sleep_init(void __iomem *reg_base) {}
>  #endif
>  
> +void __iomem *mode_con_reg;
> +static int rk3288_restart_notify(struct notifier_block *this,
> +				   unsigned long mode, void *cmd)
> +{
> +	writel(0xf3030000, mode_con_reg);
> +	return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block rk3288_restart_handler = {
> +	.notifier_call = rk3288_restart_notify,
> +	/* Switch PLLs other than DPLL (for SDRAM) to slow mode before reboot
> +	 * to avoid crashes in reset, so this priority must bigger than the one
> +	 * in rockchip_restart_handler.
> +	 */
> +	.priority = 129,
> +};
> +
> +void __init rk3288_register_restart_notifier(void __iomem *reg)
> +{
> +	int ret;
> +
> +	mode_con_reg = reg;
> +	ret = register_restart_handler(&rk3288_restart_handler);
> +	if (ret)
> +		pr_err("%s: cannot register restart handler, %d\n",
> +		       __func__, ret);
> +}
> +

restart_handlers are really _only_ supposed to be used for actions actually 
restarting the system, not stuff that needs to be done before.

In the rockchip clock case, we already have the syscore_ops defined doing the 
suspend/resume handling, so you could simply define a .shutdown callback which 
also gets called from kernel_restart() [0], so runs at nearly the same time.

Heiko

[0] http://lxr.free-electrons.com/source/kernel/reboot.c#L214