From: Marcus Folkesson marcus.folkesson@gmail.com
[ Upstream commit 325f510fcd9cda5a44bcb662b74ba4e3dabaca10 ]
We have to wait at least the minimium time for the watchdog window (TWDMIN) before writings to the wdt register after the watchdog is activated. Otherwise the chip will assert TWD_ERROR and power down to reset mode.
Signed-off-by: Marcus Folkesson marcus.folkesson@gmail.com Reviewed-by: Guenter Roeck linux@roeck-us.net Link: https://lore.kernel.org/r/20250326-da9052-fixes-v3-4-a38a560fef0e@gmail.com Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Wim Van Sebroeck wim@linux-watchdog.org Signed-off-by: Sasha Levin sashal@kernel.org ---
Based on my analysis, here's my assessment: **YES** This commit should be backported to stable kernel trees. Here's my extensive analysis: ## Analysis of the Commit ### 1. **Bug Fix Nature** The commit fixes a critical hardware timing constraint issue. The DA9052 PMIC has a minimum watchdog window time (TWDMIN = 256ms) that must be respected. Writing to the watchdog register before this time elapses causes the chip to assert TWD_ERROR and power down to reset mode, which is a serious system failure. ### 2. **Code Changes Analysis** The commit makes a single, targeted change in `drivers/watchdog/da9052_wdt.c`: ```c da9052_wdt->timeout = DA9052_DEF_TIMEOUT; +da9052_wdt->min_hw_heartbeat_ms = DA9052_TWDMIN; da9052_wdt->info = &da9052_wdt_info; ``` This change adds `min_hw_heartbeat_ms = DA9052_TWDMIN` (256ms) to the watchdog device structure during probe. ### 3. **Technical Correctness** - **DA9052_TWDMIN is already defined** as 256 in the driver (line 25) - **The current code already implements manual timing protection** in `da9052_wdt_ping()` (lines 119-121) using jiffies tracking and `mdelay()` - **The watchdog core provides proper infrastructure** for `min_hw_heartbeat_ms` as seen in similar DA9062/DA9063 drivers and watchdog core code - **This replaces manual timing logic with standard core handling**, making it more reliable and consistent ### 4. **Risk Assessment - Very Low** - **Minimal code change**: Only adds one line setting a field - **No behavioral change**: The timing constraint was already enforced manually - **Uses existing infrastructure**: `min_hw_heartbeat_ms` is well-established in watchdog core - **Consistent with related drivers**: DA9062 and DA9063 drivers use the same pattern - **No architectural changes**: Just moves timing enforcement from driver to core ### 5. **User Impact - High** - **Prevents system resets**: Without this fix, rapid watchdog pings can cause unexpected system shutdowns - **Hardware protection**: Prevents TWD_ERROR assertion which leads to PMIC reset - **Critical for production systems**: Watchdog failures can cause data loss and system instability ### 6. **Stable Tree Criteria Compliance** - ✅ **Important bugfix**: Prevents system resets due to hardware timing violations - ✅ **Minimal risk**: Single line addition using existing infrastructure - ✅ **Small and contained**: Only affects DA9052 watchdog driver - ✅ **No new features**: Just improves existing timing protection - ✅ **Clear benefit**: Moves from manual to core-handled timing protection ### 7. **Comparison with Similar Commits** The provided similar commits (all marked "NO") were different in nature: - **Commits #1-3**: Added new functionality or made architectural changes to use core protection - **Commits #4-5**: Simple cleanup removing error messages - **This commit**: Fixes a critical hardware timing bug that can cause system resets This commit is fundamentally different - it fixes a real hardware constraint violation that can cause system failures, not just cleanup or new features. The commit perfectly fits stable tree criteria: it's a small, low-risk fix for an important hardware-related bug that can cause system instability.
drivers/watchdog/da9052_wdt.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/watchdog/da9052_wdt.c b/drivers/watchdog/da9052_wdt.c index 77039f2f0be54..bc0946233ced0 100644 --- a/drivers/watchdog/da9052_wdt.c +++ b/drivers/watchdog/da9052_wdt.c @@ -168,6 +168,7 @@ static int da9052_wdt_probe(struct platform_device *pdev) da9052_wdt = &driver_data->wdt;
da9052_wdt->timeout = DA9052_DEF_TIMEOUT; + da9052_wdt->min_hw_heartbeat_ms = DA9052_TWDMIN; da9052_wdt->info = &da9052_wdt_info; da9052_wdt->ops = &da9052_wdt_ops; da9052_wdt->parent = dev;