[PATCH 1/2] watchdog: sama5d4: fix shared IRQ and hardcoded timeout issues

[Rosen Penev <rosenp@gmail.com>]

Fix three pre-existing issues in the sama5d4 watchdog driver:

1. Unsafe IRQF_SHARED | IRQF_NO_SUSPEND combination: The watchdog
   interrupt is a dedicated peripheral line, not shared with other
   devices.  Drop IRQF_SHARED to avoid the documented unsafe interaction
   where IRQF_NO_SUSPEND keeps the line enabled during suspend while
   other sharing devices may be powered down.

2. Unconditional IRQ_HANDLED on shared line: The handler returned
   IRQ_HANDLED even when the status register indicated no watchdog
   interrupt was pending.  Return IRQ_NONE in that case so the kernel
   can properly detect spurious interrupts on the line.

3. Hardcoded 16-second timeout: sama5d4_wdt_init() unconditionally
   used WDT_DEFAULT_TIMEOUT (16s) for the hardware timeout, ignoring
   any timeout configured via device tree (watchdog_init_timeout) or
   userspace.  Pass wdd->timeout to sama5d4_wdt_init() so the
   configured timeout is honored during probe and resume.

Assisted-by: opencode:big-pickle
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/watchdog/sama5d4_wdt.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
index 704b786cc2ec..b7a8cfed335d 100644
--- a/drivers/watchdog/sama5d4_wdt.c
+++ b/drivers/watchdog/sama5d4_wdt.c
@@ -169,11 +169,12 @@ static irqreturn_t sama5d4_wdt_irq_handler(int irq, void *dev_id)
 	else
 		reg = wdt_read(wdt, AT91_WDT_SR);
 
-	if (reg) {
-		pr_crit("Atmel Watchdog Software Reset\n");
-		emergency_restart();
-		pr_crit("Reboot didn't succeed\n");
-	}
+	if (!reg)
+		return IRQ_NONE;
+
+	pr_crit("Atmel Watchdog Software Reset\n");
+	emergency_restart();
+	pr_crit("Reboot didn't succeed\n");
 
 	return IRQ_HANDLED;
 }
@@ -197,11 +198,11 @@ static int of_sama5d4_wdt_init(struct device_node *np, struct sama5d4_wdt *wdt)
 	return 0;
 }
 
-static int sama5d4_wdt_init(struct sama5d4_wdt *wdt)
+static int sama5d4_wdt_init(struct sama5d4_wdt *wdt, unsigned int timeout)
 {
 	u32 reg, val;
 
-	val = WDT_SEC2TICKS(WDT_DEFAULT_TIMEOUT);
+	val = WDT_SEC2TICKS(timeout);
 	/*
 	 * When booting and resuming, the bootloader may have changed the
 	 * watchdog configuration.
@@ -289,8 +290,8 @@ static int sama5d4_wdt_probe(struct platform_device *pdev)
 
 	if (wdt->need_irq) {
 		ret = devm_request_irq(dev, irq, sama5d4_wdt_irq_handler,
-				       IRQF_SHARED | IRQF_IRQPOLL |
-				       IRQF_NO_SUSPEND, pdev->name, pdev);
+				       IRQF_IRQPOLL | IRQF_NO_SUSPEND,
+				       pdev->name, pdev);
 		if (ret) {
 			dev_err(dev, "cannot register interrupt handler\n");
 			return ret;
@@ -305,7 +306,7 @@ static int sama5d4_wdt_probe(struct platform_device *pdev)
 		set_bit(WDOG_HW_RUNNING, &wdd->status);
 	}
 
-	ret = sama5d4_wdt_init(wdt);
+	ret = sama5d4_wdt_init(wdt, wdd->timeout);
 	if (ret)
 		return ret;
 
@@ -358,7 +359,7 @@ static int sama5d4_wdt_resume_early(struct device *dev)
 	 * This should only be done when the registers are lost on suspend but
 	 * there is no way to get this information right now.
 	 */
-	sama5d4_wdt_init(wdt);
+	sama5d4_wdt_init(wdt, wdt->wdd.timeout);
 
 	if (watchdog_active(&wdt->wdd))
 		sama5d4_wdt_start(&wdt->wdd);
-- 
2.54.0