[PATCHv2 3/5] watchdog: rti-wdt: add support for window size configuration

[Tero Kristo <t-kristo@ti.com>]

RTI watchdog can support different open window sizes. Add support for
these and add a new module parameter to configure it. The default open
window size for the driver still remains at 50%.

Also, modify the margin calculation logic a bit for 32k source clock,
instead of adding a margin to every window config, assume the 32k source
clock is running slower.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
---
 drivers/watchdog/rti_wdt.c | 112 +++++++++++++++++++++++++++++++------
 1 file changed, 95 insertions(+), 17 deletions(-)

diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
index d456dd72d99a..110bfc8d0bb3 100644
--- a/drivers/watchdog/rti_wdt.c
+++ b/drivers/watchdog/rti_wdt.c
@@ -19,7 +19,8 @@
 #include <linux/types.h>
 #include <linux/watchdog.h>
 
-#define DEFAULT_HEARTBEAT 60
+#define DEFAULT_HEARTBEAT	60
+#define DEFAULT_WINDOWSIZE	50
 
 /* Max heartbeat is calculated at 32kHz source clock */
 #define MAX_HEARTBEAT	1000
@@ -35,9 +36,13 @@
 
 #define RTIWWDRX_NMI	0xa
 
-#define RTIWWDSIZE_50P	0x50
+#define RTIWWDSIZE_50P		0x50
+#define RTIWWDSIZE_25P		0x500
+#define RTIWWDSIZE_12P5		0x5000
+#define RTIWWDSIZE_6P25		0x50000
+#define RTIWWDSIZE_3P125	0x500000
 
-#define WDENABLE_KEY	0xa98559da
+#define WDENABLE_KEY		0xa98559da
 
 #define WDKEY_SEQ0		0xe51a
 #define WDKEY_SEQ1		0xa35c
@@ -48,7 +53,8 @@
 
 #define DWDST			BIT(1)
 
-static int heartbeat;
+static int heartbeat =		DEFAULT_HEARTBEAT;
+static u32 wsize =		DEFAULT_WINDOWSIZE;
 
 /*
  * struct to hold data for each WDT device
@@ -62,34 +68,93 @@ struct rti_wdt_device {
 	struct watchdog_device	wdd;
 };
 
+static int rti_wdt_convert_wsize(void)
+{
+	if (wsize >= 50) {
+		wsize = RTIWWDSIZE_50P;
+	} else if (wsize >= 25) {
+		wsize = RTIWWDSIZE_25P;
+	} else if (wsize > 12) {
+		wsize = RTIWWDSIZE_12P5;
+	} else if (wsize > 6) {
+		wsize = RTIWWDSIZE_6P25;
+	} else if (wsize > 3) {
+		wsize = RTIWWDSIZE_3P125;
+	} else {
+		pr_err("%s: bad windowsize: %d\n", __func__, wsize);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int rti_wdt_setup_hw_hb(struct watchdog_device *wdd)
+{
+	/*
+	 * RTI only supports a windowed mode, where the watchdog can only
+	 * be petted during the open window; not too early or not too late.
+	 * The HW configuration options only allow for the open window size
+	 * to be 50% or less than that.
+	 */
+	switch (wsize) {
+	case RTIWWDSIZE_50P:
+		/* 50% open window => 50% min heartbeat */
+		wdd->min_hw_heartbeat_ms = 500 * heartbeat;
+		break;
+
+	case RTIWWDSIZE_25P:
+		/* 25% open window => 75% min heartbeat */
+		wdd->min_hw_heartbeat_ms = 750 * heartbeat;
+		break;
+
+	case RTIWWDSIZE_12P5:
+		/* 12.5% open window => 87.5% min heartbeat */
+		wdd->min_hw_heartbeat_ms = 875 * heartbeat;
+		break;
+
+	case RTIWWDSIZE_6P25:
+		/* 6.5% open window => 93.5% min heartbeat */
+		wdd->min_hw_heartbeat_ms = 935 * heartbeat;
+		break;
+
+	case RTIWWDSIZE_3P125:
+		/* 3.125% open window => 96.9% min heartbeat */
+		wdd->min_hw_heartbeat_ms = 969 * heartbeat;
+		break;
+
+	default:
+		pr_err("%s: Bad watchdog window size!\n", __func__);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int rti_wdt_start(struct watchdog_device *wdd)
 {
 	u32 timer_margin;
 	struct rti_wdt_device *wdt = watchdog_get_drvdata(wdd);
+	int ret;
 
 	/* set timeout period */
-	timer_margin = (u64)wdd->timeout * wdt->freq;
+	timer_margin = (u64)heartbeat * wdt->freq;
 	timer_margin >>= WDT_PRELOAD_SHIFT;
 	if (timer_margin > WDT_PRELOAD_MAX)
 		timer_margin = WDT_PRELOAD_MAX;
 	writel_relaxed(timer_margin, wdt->base + RTIDWDPRLD);
 
-	/*
-	 * RTI only supports a windowed mode, where the watchdog can only
-	 * be petted during the open window; not too early or not too late.
-	 * The HW configuration options only allow for the open window size
-	 * to be 50% or less than that; we obviouly want to configure the open
-	 * window as large as possible so we select the 50% option. To avoid
-	 * any glitches, we accommodate 5% safety margin also, so we setup
-	 * the min_hw_hearbeat at 55% of the timeout period.
-	 */
-	wdd->min_hw_heartbeat_ms = 11 * wdd->timeout * 1000 / 20;
+	ret = rti_wdt_convert_wsize();
+	if (ret)
+		return ret;
+
+	ret = rti_wdt_setup_hw_hb(wdd);
+	if (ret)
+		return ret;
 
 	/* Generate NMI when wdt expires */
 	writel_relaxed(RTIWWDRX_NMI, wdt->base + RTIWWDRXCTRL);
 
-	/* Open window size 50%; this is the largest window size available */
-	writel_relaxed(RTIWWDSIZE_50P, wdt->base + RTIWWDSIZECTRL);
+	writel_relaxed(wsize, wdt->base + RTIWWDSIZECTRL);
 
 	readl_relaxed(wdt->base + RTIWWDSIZECTRL);
 
@@ -169,6 +234,14 @@ static int rti_wdt_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
+	/*
+	 * If watchdog is running at 32k clock, it is not accurate.
+	 * Adjust frequency down in this case so that we don't pet
+	 * the watchdog too often.
+	 */
+	if (wdt->freq > 30000 && wdt->freq < 32768)
+		wdt->freq = 30000;
+
 	pm_runtime_enable(dev);
 	ret = pm_runtime_get_sync(dev);
 	if (ret) {
@@ -251,5 +324,10 @@ MODULE_PARM_DESC(heartbeat,
 		 __MODULE_STRING(MAX_HEARTBEAT) ", default "
 		 __MODULE_STRING(DEFAULT_HEARTBEAT));
 
+module_param(wsize, uint, 0);
+MODULE_PARM_DESC(wsize,
+		 "Watchdog open window size in percentage from 3 to 50, "
+		 "default " __MODULE_STRING(DEFAULT_WINDOW_SIZE));
+
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("platform:rti-wdt");
-- 
2.17.1

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