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

[zyw@rock-chips.com (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