[PATCH 3/4] watchdog: stm32mp: check the watchdog status

[Antonio Borneo]

From: Clément Le Goffic <clement.legof...@foss.st.com>

Add a mean to check the IWDG status based on the peripheral version.
This is done by either checking the status bit ONF either by updating
the reload register with the same value and check if the reload succeed.

Signed-off-by: Clément Le Goffic <clement.legof...@foss.st.com>
Signed-off-by: Antonio Borneo <antonio.bor...@foss.st.com>
---
 drivers/watchdog/stm32mp_wdt.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/watchdog/stm32mp_wdt.c b/drivers/watchdog/stm32mp_wdt.c
index 97ab8cfe7ab..0712524b4a8 100644
--- a/drivers/watchdog/stm32mp_wdt.c
+++ b/drivers/watchdog/stm32mp_wdt.c
@@ -21,11 +21,13 @@
 #define IWDG_PR                0x04    /* Prescaler Register */
 #define IWDG_RLR       0x08    /* ReLoad Register */
 #define IWDG_SR                0x0C    /* Status Register */
+#define IWDG_VERR      0x3F4   /* Version Register */
 
 /* IWDG_KR register bit mask */
 #define KR_KEY_RELOAD  0xAAAA  /* Reload counter enable */
 #define KR_KEY_ENABLE  0xCCCC  /* Peripheral enable */
 #define KR_KEY_EWA     0x5555  /* Write access enable */
+#define KR_KEY_DWA     0x0000  /* Write access disable*/
 
 /* IWDG_PR register bit values */
 #define PR_256         0x06    /* Prescaler set to 256 */
@@ -36,10 +38,17 @@
 /* IWDG_SR register bit values */
 #define SR_PVU         BIT(0)  /* Watchdog prescaler value update */
 #define SR_RVU         BIT(1)  /* Watchdog counter reload value update */
+#define SR_ONF         BIT(8)  /* Watchdog enable status bit */
+
+/* IWDG Compatibility */
+#define ONF_MIN_VER    0x31
+
+#define TIMEOUT_US     10000
 
 struct stm32mp_wdt_priv {
        fdt_addr_t base;                /* registers addr in physical memory */
        unsigned long wdt_clk_rate;     /* Watchdog dedicated clock rate */
+       unsigned int hw_version;        /* Peripheral version */
 };
 
 static int stm32mp_wdt_reset(struct udevice *dev)
@@ -90,6 +99,7 @@ static int stm32mp_wdt_start(struct udevice *dev, u64 
timeout_ms, ulong flags)
 static int stm32mp_wdt_probe(struct udevice *dev)
 {
        struct stm32mp_wdt_priv *priv = dev_get_priv(dev);
+       u32 rlr, sr;
        struct clk clk;
        int ret;
 
@@ -115,6 +125,29 @@ static int stm32mp_wdt_probe(struct udevice *dev)
 
        priv->wdt_clk_rate = clk_get_rate(&clk);
 
+       priv->hw_version = readl(priv->base + IWDG_VERR);
+
+       if (priv->hw_version >= ONF_MIN_VER) {
+               if (readl(priv->base + IWDG_SR) & SR_ONF)
+                       wdt_set_force_autostart(dev);
+       } else {
+               /*
+                * Workaround for old versions without IWDG_SR_ONF bit:
+                * - write in IWDG_RLR_OFFSET
+                * - wait for sync
+                * - if sync succeeds, then iwdg is running
+                */
+               writel(KR_KEY_EWA, priv->base + IWDG_KR);
+               rlr = readl(priv->base + IWDG_RLR);
+               writel(rlr, priv->base + IWDG_RLR);
+               ret = readl_poll_timeout(priv->base + IWDG_SR, sr, sr & SR_RVU,
+                                        TIMEOUT_US);
+               if (!ret)
+                       wdt_set_force_autostart(dev);
+
+               writel(KR_KEY_DWA, priv->base + IWDG_KR);
+       }
+
        dev_dbg(dev, "IWDG init done\n");
 
        return 0;
-- 
2.34.1