[PATCH 2/7] sandbox: fix probe order dependency between watchdog and power

[Ahmad Fatoum]

With incoming changes to enable deep probe for sandbox, watchdog driver
may be probed before power driver, which so far didn't happen. Because
the watchdog driver writes the same NVMEM cell read by the power driver,
the original value of the nvmem cell (used for $global.system.reset)
will be lost. Work around this by writing the WDG reset reason only
at first watchdog enable which is guaranteed to happen after power
driver probe. We don't need to reset the nvmem cell on watchdog disable,
because all other reset methods will already overwrite the cell with
the correct value.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 arch/sandbox/board/watchdog.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/sandbox/board/watchdog.c b/arch/sandbox/board/watchdog.c
index ff26a2019fac..daaf549642e3 100644
--- a/arch/sandbox/board/watchdog.c
+++ b/arch/sandbox/board/watchdog.c
@@ -12,6 +12,7 @@
 struct sandbox_watchdog {
 	struct watchdog wdd;
 	bool cant_disable :1;
+	struct nvmem_cell *reset_source_cell;
 };
 
 static inline struct sandbox_watchdog *to_sandbox_watchdog(struct watchdog *wdd)
@@ -29,6 +30,8 @@ static int sandbox_watchdog_set_timeout(struct watchdog *wdd, unsigned int timeo
 	if (timeout > wdd->timeout_max)
 		return -EINVAL;
 
+	nvmem_cell_write(wd->reset_source_cell, &(u8) { RESET_WDG }, 1);
+
 	linux_watchdog_set_timeout(timeout);
 	return 0;
 }
@@ -36,7 +39,6 @@ static int sandbox_watchdog_set_timeout(struct watchdog *wdd, unsigned int timeo
 static int sandbox_watchdog_probe(struct device_d *dev)
 {
 	struct device_node *np = dev->device_node;
-	struct nvmem_cell *reset_source_cell;
 	struct sandbox_watchdog *wd;
 	struct watchdog *wdd;
 	int ret;
@@ -56,16 +58,12 @@ static int sandbox_watchdog_probe(struct device_d *dev)
 		return ret;
 	}
 
-	reset_source_cell = of_nvmem_cell_get(dev->device_node, "reset-source");
-	if (IS_ERR(reset_source_cell)) {
-		dev_warn(dev, "No reset source info available: %pe\n", reset_source_cell);
+	wd->reset_source_cell = of_nvmem_cell_get(dev->device_node, "reset-source");
+	if (IS_ERR(wd->reset_source_cell)) {
+		dev_warn(dev, "No reset source info available: %pe\n", wd->reset_source_cell);
 		goto out;
 	}
 
-	nvmem_cell_write(reset_source_cell, &(u8) { RESET_WDG }, 1);
-
-	nvmem_cell_put(reset_source_cell);
-
 out:
 	dev_info(dev, "probed\n");
 	return 0;
-- 
2.30.2