[PATCH 1/2] watchdog: versal: Add support for basic window watchdog

[Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>]

Existing driver uses generic watchdog mode which generates a signal to
PLM firmware, but the signal cannot be used to reset the system.

Change driver to use window watchdog basic mode. This window watchdog mode
generates a signal to PLM firmware which decides what action to take upon
expiry of watchdog.

Timeout value for xlnx_wwdt_start will come in milli seconds from wdt
framework. Make changes to load count value accordingly.

Add checks before loading the timer for min and max possible values.

Fix authour email id of Ashok Reddy Soma to long email id.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
---

 drivers/watchdog/xilinx_wwdt.c | 98 +++++++++++++++++++++-------------
 1 file changed, 60 insertions(+), 38 deletions(-)

diff --git a/drivers/watchdog/xilinx_wwdt.c b/drivers/watchdog/xilinx_wwdt.c
index c8e6c60cdd..d8b2ae7248 100644
--- a/drivers/watchdog/xilinx_wwdt.c
+++ b/drivers/watchdog/xilinx_wwdt.c
@@ -3,7 +3,7 @@
  * Xilinx window watchdog timer driver.
  *
  * Author(s):	Michal Simek <michal.simek@xilinx.com>
- *		Ashok Reddy Soma <ashokred@xilinx.com>
+ *		Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
  *
  * Copyright (c) 2020, Xilinx Inc.
  */
@@ -23,13 +23,22 @@
 /* Generic Control/Status Register Masks */
 #define XWT_WWCSR_GWEN_MASK	BIT(0) /* Enable Bit */
 
-/* Register offsets for the Wdt device */
-#define XWT_WWREF_OFFSET	0x1000 /* Refresh Register */
-#define XWT_WWCSR_OFFSET	0x2000 /* Control/Status Register */
-#define XWT_WWOFF_OFFSET	0x2008 /* Offset Register */
-#define XWT_WWCMP0_OFFSET	0x2010 /* Compare Value Register0 */
-#define XWT_WWCMP1_OFFSET	0x2014 /* Compare Value Register1 */
-#define XWT_WWWRST_OFFSET	0x2FD0 /* Warm Reset Register */
+/* Register offsets for the WWDT device */
+#define XWT_WWDT_MWR_OFFSET	0x00
+#define XWT_WWDT_ESR_OFFSET	0x04
+#define XWT_WWDT_FCR_OFFSET	0x08
+#define XWT_WWDT_FWR_OFFSET	0x0c
+#define XWT_WWDT_SWR_OFFSET	0x10
+#define XWT_WWDT_CNT_MIN	1
+#define XWT_WWDT_CNT_MAX	0xffffffff
+
+/* Master Write Control Register Masks */
+#define XWT_WWDT_MWR_MASK	BIT(0)
+
+/* Enable and Status Register Masks */
+#define XWT_WWDT_ESR_WINT_MASK	BIT(16)
+#define XWT_WWDT_ESR_WSW_MASK	BIT(8)
+#define XWT_WWDT_ESR_WEN_MASK	BIT(0)
 
 struct xlnx_wwdt_priv {
 	bool enable_once;
@@ -43,16 +52,23 @@ struct xlnx_wwdt_plat {
 
 static int xlnx_wwdt_reset(struct udevice *dev)
 {
+	u32 esr;
 	struct xlnx_wwdt_priv *wdt = dev_get_priv(dev);
 
-	regmap_write(wdt->regs, XWT_WWREF_OFFSET, XWT_WWREF_GWRR_MASK);
+	regmap_write(wdt->regs, XWT_WWDT_MWR_OFFSET, XWT_WWDT_MWR_MASK);
+	regmap_read(wdt->regs, XWT_WWDT_ESR_OFFSET, &esr);
+	esr |= XWT_WWDT_ESR_WINT_MASK;
+	esr &= ~XWT_WWDT_ESR_WSW_MASK;
+	regmap_write(wdt->regs, XWT_WWDT_ESR_OFFSET, esr);
+	regmap_read(wdt->regs, XWT_WWDT_ESR_OFFSET, &esr);
+	esr |= XWT_WWDT_ESR_WSW_MASK;
+	regmap_write(wdt->regs, XWT_WWDT_ESR_OFFSET, esr);
 
 	return 0;
 }
 
 static int xlnx_wwdt_stop(struct udevice *dev)
 {
-	u32 csr;
 	struct xlnx_wwdt_priv *wdt = dev_get_priv(dev);
 
 	if (wdt->enable_once) {
@@ -60,10 +76,9 @@ static int xlnx_wwdt_stop(struct udevice *dev)
 		return -EBUSY;
 	}
 
-	/* Disable the generic watchdog timer */
-	regmap_read(wdt->regs, XWT_WWCSR_OFFSET, &csr);
-	csr &= ~(XWT_WWCSR_GWEN_MASK);
-	regmap_write(wdt->regs, XWT_WWCSR_OFFSET, csr);
+	/* Disable the  window watchdog timer */
+	regmap_write(wdt->regs, XWT_WWDT_MWR_OFFSET, XWT_WWDT_MWR_MASK);
+	regmap_write(wdt->regs, XWT_WWDT_ESR_OFFSET, ~(u32)XWT_WWDT_ESR_WEN_MASK);
 
 	clk_disable(&wdt->clk);
 
@@ -72,11 +87,11 @@ static int xlnx_wwdt_stop(struct udevice *dev)
 	return 0;
 }
 
-static int xlnx_wwdt_start(struct udevice *dev, u64 timeout, ulong flags)
+static int xlnx_wwdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
 {
 	int ret;
-	u32 csr;
-	u64 count;
+	u32 esr;
+	u64 count, timeout;
 	unsigned long clock_f;
 	struct xlnx_wwdt_priv *wdt = dev_get_priv(dev);
 
@@ -88,36 +103,43 @@ static int xlnx_wwdt_start(struct udevice *dev, u64 timeout, ulong flags)
 
 	dev_dbg(dev, "%s: CLK %ld\n", __func__, clock_f);
 
+	/* Convert timeout from msec to sec */
+	timeout = timeout_ms / 1000;
+
 	/* Calculate timeout count */
 	count = timeout * clock_f;
 
+	/* Count should be at least 1 */
+	if (count < XWT_WWDT_CNT_MIN) {
+		debug("%s: watchdog won't fire with 0 ticks\n", __func__);
+		count = XWT_WWDT_CNT_MIN;
+	}
+
+	/* Limit the count to maximum possible value */
+	if (count > XWT_WWDT_CNT_MAX) {
+		debug("%s: maximum watchdog timeout exceeded\n", __func__);
+		count = XWT_WWDT_CNT_MAX;
+	}
+
 	ret = clk_enable(&wdt->clk);
 	if (ret) {
 		dev_err(dev, "failed to enable clock\n");
 		return ret;
 	}
 
-	/*
-	 * Timeout count is half as there are two windows
-	 * first window overflow is ignored (interrupt),
-	 * reset is only generated at second window overflow
-	 */
-	count = count >> 1;
-
-	/* Disable the generic watchdog timer */
-	regmap_read(wdt->regs, XWT_WWCSR_OFFSET, &csr);
-	csr &= ~(XWT_WWCSR_GWEN_MASK);
-	regmap_write(wdt->regs, XWT_WWCSR_OFFSET, csr);
-
-	/* Set compare and offset registers for generic watchdog timeout */
-	regmap_write(wdt->regs, XWT_WWCMP0_OFFSET, (u32)count);
-	regmap_write(wdt->regs, XWT_WWCMP1_OFFSET, 0);
-	regmap_write(wdt->regs, XWT_WWOFF_OFFSET, (u32)count);
-
-	/* Enable the generic watchdog timer */
-	regmap_read(wdt->regs, XWT_WWCSR_OFFSET, &csr);
-	csr |= (XWT_WWCSR_GWEN_MASK);
-	regmap_write(wdt->regs, XWT_WWCSR_OFFSET, csr);
+	/* Disable the window watchdog timer */
+	regmap_write(wdt->regs, XWT_WWDT_MWR_OFFSET, XWT_WWDT_MWR_MASK);
+	regmap_write(wdt->regs, XWT_WWDT_ESR_OFFSET, ~(u32)XWT_WWDT_ESR_WEN_MASK);
+
+	/* Set first window and second window registers with timeout */
+	regmap_write(wdt->regs, XWT_WWDT_FWR_OFFSET, 0); /* No pre-timeout */
+	regmap_write(wdt->regs, XWT_WWDT_SWR_OFFSET, (u32)count);
+	regmap_write(wdt->regs, XWT_WWDT_FCR_OFFSET, 0);
+
+	/* Enable the window watchdog timer */
+	regmap_read(wdt->regs, XWT_WWDT_ESR_OFFSET, &esr);
+	esr |= XWT_WWDT_ESR_WEN_MASK;
+	regmap_write(wdt->regs, XWT_WWDT_ESR_OFFSET, esr);
 
 	return 0;
 }
-- 
2.17.1