Re: [PATCH v2 1/3] watchdog: imx2_wdg: suspend watchdog in WAIT mode

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On 25. 10. 22 16:21, Guenter Roeck wrote:
On 10/25/22 00:25, Andrej Picej wrote:
Putting device into the "Suspend-To-Idle" mode causes watchdog to
trigger and reset the board after set watchdog timeout period elapses.


s/reset/resets/

Introduce new device-tree property "fsl,suspend-in-wait" which suspends
watchdog in WAIT mode. This is done by setting WDW bit in WCR
(Watchdog Control Register) Watchdog operation is restored after exiting

'.' after ')' missing ?

WAIT mode as expected. WAIT mode coresponds with Linux's

s/coresponds/corresponds/

Will fix this in v3, thank you.

"Suspend-To-Idle".

Signed-off-by: Andrej Picej <andrej.picej@xxxxxxxxx>
Reviewed-by: Fabio Estevam <festevam@xxxxxxxxx>
---
Changes in v2:
  - validate the property with compatible string, as this functionality
    is not supported by all devices.
---
  drivers/watchdog/imx2_wdt.c | 37 +++++++++++++++++++++++++++++++++++++
  1 file changed, 37 insertions(+)

diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
index d0c5d47ddede..dd9866c6f1e5 100644
--- a/drivers/watchdog/imx2_wdt.c
+++ b/drivers/watchdog/imx2_wdt.c
@@ -35,6 +35,7 @@
  #define IMX2_WDT_WCR        0x00        /* Control Register */
  #define IMX2_WDT_WCR_WT        (0xFF << 8)    /* -> Watchdog Timeout Field */ +#define IMX2_WDT_WCR_WDW    BIT(7)        /* -> Watchdog disable for WAIT */   #define IMX2_WDT_WCR_WDA    BIT(5)        /* -> External Reset WDOG_B */   #define IMX2_WDT_WCR_SRS    BIT(4)        /* -> Software Reset Signal */
  #define IMX2_WDT_WCR_WRE    BIT(3)        /* -> WDOG Reset Enable */
@@ -67,6 +68,27 @@ struct imx2_wdt_device {
      bool ext_reset;
      bool clk_is_on;
      bool no_ping;
+    bool sleep_wait;
+};
+
+static const char * const wdw_boards[] __initconst = {
+    "fsl,imx25-wdt",
+    "fsl,imx35-wdt",
+    "fsl,imx50-wdt",
+    "fsl,imx51-wdt",
+    "fsl,imx53-wdt",
+    "fsl,imx6q-wdt",
+    "fsl,imx6sl-wdt",
+    "fsl,imx6sll-wdt",
+    "fsl,imx6sx-wdt",
+    "fsl,imx6ul-wdt",
+    "fsl,imx7d-wdt",
+    "fsl,imx8mm-wdt",
+    "fsl,imx8mn-wdt",
+    "fsl,imx8mp-wdt",
+    "fsl,imx8mq-wdt",
+    "fsl,vf610-wdt",
+    NULL
  };
  static bool nowayout = WATCHDOG_NOWAYOUT;
@@ -129,6 +151,9 @@ static inline void imx2_wdt_setup(struct watchdog_device *wdog)
      /* Suspend timer in low power mode, write once-only */
      val |= IMX2_WDT_WCR_WDZST;
+    /* Suspend timer in low power WAIT mode, write once-only */
+    if (wdev->sleep_wait)
+        val |= IMX2_WDT_WCR_WDW;
      /* Strip the old watchdog Time-Out value */
      val &= ~IMX2_WDT_WCR_WT;
      /* Generate internal chip-level reset if WDOG times out */
@@ -313,6 +338,18 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
      wdev->ext_reset = of_property_read_bool(dev->of_node,
                          "fsl,ext-reset-output");
+
+    if (of_property_read_bool(dev->of_node, "fsl,suspend-in-wait"))
+        if (of_device_compatible_match(dev->of_node, wdw_boards))
+            wdev->sleep_wait = 1;

Since sleep_wait is bool:
             wdev->sleep_wait = true;

+        else {
+            dev_warn(dev, "Warning: Suspending watchdog during " \
+                "WAIT mode is not supported for this device.\n");

Do not split strings. "Warning:" is redundant. Please handle the error first.

+            wdev->sleep_wait = 0;

Unnecessary; false by default. Also, this should fail and return -EINVAL.
Devicetree files should be correct, and warning messages tend to be ignored.

+        }

All branches of if/else need to wither use {} or no {}.

+    else
+        wdev->sleep_wait = 0;
+
Unnecessary.

I would suggest to replace the above code with something like

     if (of_property_read_bool(dev->of_node, "fsl,suspend-in-wait")) {
         if (!of_device_compatible_match(dev->of_node, wdw_boards)) {
            dev_err(dev, "Suspending watchdog in WAIT mode is not supported for this device\n");
             return -EINVAL;
         }
         wdev->sleep_wait = true;
     }

OK, this look cleaner, will use this, thanks.


      /*
       * The i.MX7D doesn't support low power mode, so we need to ping the watchdog
       * during suspend.

I still wonder how that interacts with fsl,suspend-in-wait, but since we have a property for that we can leave that for someone else to find out. Maybe add a
comment explaining that interaction with "fsl,suspend-in-wait" is unknown.
I'm assuming that i.MX7D doesn't enter any of low-power modes including WAIT mode. If this is the case the watchdog wouldn't get disabled.

Anyway, I will add a short comment regarding the unknown behaviour of this property with i.MX7D device.

Best regards,
Andrej



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