[PATCH 5.10 5.4 4.19 4.14] watchdog: sbsa_wdog: Make sure the timeout programming is within the limits

["Tyler Hicks (Microsoft)" <code@tyhicks.com>]

From: George Cherian <george.cherian@marvell.com>

[ Upstream commit 000987a38b53c172f435142a4026dd71378ca464 ]

Make sure to honour the max_hw_heartbeat_ms while programming the timeout
value to WOR. Clamp the timeout passed to sbsa_gwdt_set_timeout() to
make sure the programmed value is within the permissible range.

Fixes: abd3ac7902fb ("watchdog: sbsa: Support architecture version 1")

Signed-off-by: George Cherian <george.cherian@marvell.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230209021117.1512097-1-george.cherian@marvell.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Signed-off-by: Tyler Hicks (Microsoft) <code@tyhicks.com>
---

The Fixes line in the original commit is incorrect. This commit fixes a
bug that goes all the way back to v4.6 commit 57d2caaabfc7 ("Watchdog:
introduce ARM SBSA watchdog driver") when only 32-bit Watchdog Offset
Registers (WOR) were supported.

Without this fix, there's a truncation on the first argument, of u32
type, passed to writel() in the following situation situation:

Generic Watchdog architecture version is 1 (WOR is 32-bit)
action is 1
timeout is 240s
CNTFRQ_EL0 is 25000050 Hz
wdd.max_hw_heartbeat_ms is 171s

25000050 * 240 = 6000012000  <--- requires 33 bits to store
6000012000 & 0xFFFFFFFF = 1705044704  <--- truncated value written to WOR
1705044704 / 25000050 = 68.2s  <--- timeout incorrectly set to 68.2s

The timeout from userspace is greater than wdd.max_hw_heartbeat_ms so
the watchdog core pings at 69s (240 - 171) which results in
intermittent and unexpected panics (action=1).

With this patch applied, the timeout passed to writel() never exceeds
32-bits and the watchdog core + systemd keeps the watchdog happy.

I've validated this fix on real hardware running a linux-5.10.y stable
kernel. Please apply this patch to 5.10 through 4.14. Thanks!

Tyler

 drivers/watchdog/sbsa_gwdt.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/watchdog/sbsa_gwdt.c b/drivers/watchdog/sbsa_gwdt.c
index f0f1e3b2e463..4cbe6ba52754 100644
--- a/drivers/watchdog/sbsa_gwdt.c
+++ b/drivers/watchdog/sbsa_gwdt.c
@@ -121,6 +121,7 @@ static int sbsa_gwdt_set_timeout(struct watchdog_device *wdd,
 	struct sbsa_gwdt *gwdt = watchdog_get_drvdata(wdd);
 
 	wdd->timeout = timeout;
+	timeout = clamp_t(unsigned int, timeout, 1, wdd->max_hw_heartbeat_ms / 1000);
 
 	if (action)
 		writel(gwdt->clk * timeout,
-- 
2.34.1