[PATCH 1/2] watchdog: imx7ulp: Strictly follow the sequence for wdog operations

[Anson Huang]

According to reference manual, the i.MX7ULP WDOG's operations should
follow below sequence:

1. disable global interrupts;
2. unlock the wdog and wait unlock bit set;
3. reconfigure the wdog and wait for reconfiguration bit set;
4. enabel global interrupts.

Strictly follow the recommended sequence can make it more robust.

Signed-off-by: Anson Huang <anson.hu...@nxp.com>
---
 drivers/watchdog/imx7ulp_wdt.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/watchdog/imx7ulp_wdt.c b/drivers/watchdog/imx7ulp_wdt.c
index 7993c8c..b414ecf 100644
--- a/drivers/watchdog/imx7ulp_wdt.c
+++ b/drivers/watchdog/imx7ulp_wdt.c
@@ -4,6 +4,7 @@
  */
 
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -48,17 +49,32 @@ struct imx7ulp_wdt_device {
        struct clk *clk;
 };
 
+static inline void imx7ulp_wdt_wait(void __iomem *base, u32 mask)
+{
+       int retries = 100;
+
+       do {
+               if (readl_relaxed(base + WDOG_CS) & mask)
+                       return;
+               usleep_range(200, 1000);
+       } while (retries--);
+}
+
 static void imx7ulp_wdt_enable(struct watchdog_device *wdog, bool enable)
 {
        struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
 
        u32 val = readl(wdt->base + WDOG_CS);
 
+       local_irq_disable();
        writel(UNLOCK, wdt->base + WDOG_CNT);
+       imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK);
        if (enable)
                writel(val | WDOG_CS_EN, wdt->base + WDOG_CS);
        else
                writel(val & ~WDOG_CS_EN, wdt->base + WDOG_CS);
+       imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS);
+       local_irq_enable();
 }
 
 static bool imx7ulp_wdt_is_enabled(void __iomem *base)
@@ -72,7 +88,12 @@ static int imx7ulp_wdt_ping(struct watchdog_device *wdog)
 {
        struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
 
+       local_irq_disable();
+       writel(UNLOCK, wdt->base + WDOG_CNT);
+       imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK);
        writel(REFRESH, wdt->base + WDOG_CNT);
+       imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS);
+       local_irq_enable();
 
        return 0;
 }
@@ -98,8 +119,12 @@ static int imx7ulp_wdt_set_timeout(struct watchdog_device 
*wdog,
        struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
        u32 val = WDOG_CLOCK_RATE * timeout;
 
+       local_irq_disable();
        writel(UNLOCK, wdt->base + WDOG_CNT);
+       imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK);
        writel(val, wdt->base + WDOG_TOVAL);
+       imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS);
+       local_irq_enable();
 
        wdog->timeout = timeout;
 
@@ -140,15 +165,19 @@ static void imx7ulp_wdt_init(void __iomem *base, unsigned 
int timeout)
 {
        u32 val;
 
+       local_irq_disable();
        /* unlock the wdog for reconfiguration */
        writel_relaxed(UNLOCK_SEQ0, base + WDOG_CNT);
        writel_relaxed(UNLOCK_SEQ1, base + WDOG_CNT);
+       imx7ulp_wdt_wait(base, WDOG_CS_ULK);
 
        /* set an initial timeout value in TOVAL */
        writel(timeout, base + WDOG_TOVAL);
        /* enable 32bit command sequence and reconfigure */
        val = WDOG_CS_CMD32EN | WDOG_CS_CLK | WDOG_CS_UPDATE;
        writel(val, base + WDOG_CS);
+       imx7ulp_wdt_wait(base, WDOG_CS_RCS);
+       local_irq_enable();
 }
 
 static void imx7ulp_wdt_action(void *data)
-- 
2.7.4